qq_26296197
qq_26296197

SQLite_Android

1.SQLite概述

SQLite是一款轻量级的关系型数据库，由于它占用的资源非常少，所以在很多嵌入式设备都是用SQLite来存储数据。Android作为目前主流的移动操作系统，完全符合SQLite占用资源少的优势，故在Android平台上，集成了一个嵌入式关系型数据库SQLite。

继承SQLiteOpenHelper类，同时覆盖onCreate(SQLiteDatabase)，onUpgrade(SQLiteDatabase,int,int)和定义构造函数，使用该类实例对象的getReadableDatabase()或者getWritableDatabase()得到当前数据库的实例化对象，可直接对其进行操作

2.SQLite实现增删改查

[java] view plaincopy
  1. //数据库的基本操作，增删改查  
  2. @Override  
  3. protected void onCreate(Bundle savedInstanceState) {  
  4.     super.onCreate(savedInstanceState);  
  5.     setContentView(R.layout.activity_main);  
  6.       
  7.     DbOpenHelper dbOpenHelper = new DbOpenHelper(this, "mytest.db", 1);  
  8.     SQLiteDatabase db = dbOpenHelper.getWritableDatabase();  
  9.       
  10.     //////////////////////////////////////////////////////////  
  11.     db.execSQL("insert into user(name, age) values(?,?)",new Object[]{"zhang", 10});        //1.1增  
  12.       
  13.     db.execSQL("delete from user where _id = ?",new String[]{"1"});                         //1.2删  
  14.   
  15.     db.execSQL("update user set name=? where _id=?",new String[]{"haha", "2"});             //1.3改  
  16.   
  17.     Cursor cursor = db.rawQuery("select * from user where age >= ?", new String[]{"1"}); //1.4查  
  18.     while(cursor.moveToNext()){  
  19.         Toast.makeText(this, cursor.getString(1), Toast.LENGTH_SHORT).show();  
  20.     }  
  21.       
  22.     //////////////////////////////////////////////////////////  
  23.     ContentValues values = new ContentValues();                                             //2.1增  
  24.     values.put("name", "John");  
  25.     values.put("age", 20);  
  26.     db.insert("user",                   //表格名  
  27.             "name",                     //String nullColumnHack  
  28.                                         //  SQl不允许插入一个空行，当values的值为空时，将相当于执行于  
  29.                                         //  insert into age(name) values("null");  
  30.             values);                    //插入值，相当于一个键值对的集合  
  31.       
  32.     db.delete("user", "age>=? and age<=?", new String[]{"12", "18"});                     //2.2删  
  33.       
  34.     ContentValues values1 = new ContentValues();                                            //2.3改  
  35.     values.put("name", "liu");  
  36.     db.update("user", values1, "_id = ?", new String[]{"8"});  
  37.       
  38.     Cursor cursor1 = db.query("user",   //表格名                                               //2.4查  
  39.             null,                       //String[] columns 如果为空，则返回所有列  
  40.             "age >= ?",                  //String selection 查询条件  
  41.             new String[]{"15"},         //String[] selectionArgs 查询参数  
  42.             null,                       //String groupBy  
  43.             null,                       //String having  
  44.             null);                      //String orderBy  
  45.     while (cursor.moveToNext()) {  
  46.         int id = cursor1.getInt(cursor1.getColumnIndex("_id"));  
  47.         Toast.makeText(this, cursor1.getString(cursor1.getColumnIndex("name")), Toast.LENGTH_SHORT).show();  
  48.     }  
  49. }  
[java] view plaincopy
  1. /** 
  2.  * DbOpenHelper.java 
  3.  */  
  4. import android.content.Context;  
  5. import android.database.sqlite.SQLiteDatabase;  
  6. import android.database.sqlite.SQLiteOpenHelper;  
  7. public class DbOpenHelper extends SQLiteOpenHelper{  
  8.     public DbOpenHelper(Context context, String name, int version) {  
  9.         super(context, name, null, version);  
  10.     }  
  11.       
  12.     /** 
  13.      * 数据库只有在第一次创建时才调用该方法,对于一个已经存在的数据库，该方法不执行 
  14.      * SQLiteDatabase.openOrCreateDatabase() 
  15.      */  
  16.     @Override  
  17.     public void onCreate(SQLiteDatabase db) {  
  18.         String sql = "create table user(_id integer primary key autoincrement, name varchar(10), age integer)";  
  19.         db.execSQL(sql);  
  20.     }  
  21.   
  22.     /** 
  23.      * 只有当数据库的版本号增加时，才会执行到该函数 
  24.      * 初始默认数据库版本为0，当构造函数传递newVersion时，这时会有db.getVersion() 与 newVersion比较觉得该函数是否执行 
  25.      */  
  26.     @Override  
  27.     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {  
  28.     }  
  29. }  

3.getReadableDatabase()和getWritableDatabase()区别

(1).getReadableDatabase()

使用SQLiteDatabase实例对象的getReadableDatabase()方法，首先会检查数据库是否已经实例化并处于打开状态，如果满足要求直接返回数据库对象，否则试图返回一个可读写模式的数据库，但当磁盘空间已满，只能得到只读模式数据库对象

(2).getWritableDatabase()

使用SQLiteDatabase实例对象的getWritableDatabase()方法，目的是得到一个具有可读写的数据库实例对象，首先判断mDatabase是否不为空且已打开且不是只读模式，则直接返回该实例对象，否则如果mDatabase不为空则加锁，然后开始打开或创建数据库，进行版本相关操作并解锁，最后返回数据库实例对象！

总之，一般情况下，通过这两种方法获得的数据库实例对象时一样的，只有在数据库空间已满或其它情况下，通过getReadableDatabase得到的才是只读的实例对象

[java] view plaincopy
  1. //得到一个具有可读写的数据库实例对象  
  2. public synchronized SQLiteDatabase getWritableDatabase() {  
  3.     if (mDatabase != null && mDatabase.isOpen() && !mDatabase.isReadOnly()) {  
  4.         return mDatabase;       //如mDatabase不为空已打开并且不是只读模式 则返回该对象  
  5.     }  
  6.   
  7.     if (mIsInitializing) {      //判断是否正在初始化  
  8.         throw new IllegalStateException("getWritableDatabase called recursively");  
  9.     }  
  10.   
  11.     boolean success = false;    //默认为false  
  12.     SQLiteDatabase db = null;  
  13.     if (mDatabase != null)  
  14.         mDatabase.lock();       //如果mDatabase不为空则加锁 阻止其他的操作  
  15.     try {  
  16.         mIsInitializing = true; //初始化完成  
  17.         if (mName == null) {  
  18.             db = SQLiteDatabase.create(null);     
  19.         } else {  
  20.             db = mContext.openOrCreateDatabase(mName, 0, mFactory);//打开或创建数据库  
  21.         }  
  22.         int version = db.getVersion();                      //获取数据库版本(如果新创建的数据库版本为0)  
  23.         if (version != mNewVersion) {                       //获得的数据库版本号与指定的数据库版本号进行比较  
  24.             db.beginTransaction();              //开始事务  
  25.             try {  
  26.                 if (version == 0) {                         //新建的数据库版本号为0，则直接执行onCreate方法  
  27.                     onCreate(db);  
  28.                 } else {  
  29.                     onUpgrade(db, version, mNewVersion);    //如果版本号发生变化，且不是新建的数据库，则执行onUpgrade方法  
  30.                 }  
  31.                 db.setVersion(mNewVersion);                 //为当前的数据库设置新版本号  
  32.                 db.setTransactionSuccessful();  //设置事务成功提交  
  33.             } finally {  
  34.                 db.endTransaction();            //结束事务  
  35.             }  
  36.         }  
  37.   
  38.         onOpen(db);  
  39.         success = true;  
  40.         return db;                          //返回当前的可读写模式数据库实例对象  
  41.     } finally {  
  42.         mIsInitializing = false;  
  43.         if (success) {  
  44.             if (mDatabase != null) {  
  45.                 try {  
  46.                     mDatabase.close();      //如果mDatabase存在则先关闭  
  47.                 } catch (Exception e) {  
  48.                 }  
  49.                 mDatabase.unlock();         //为当前的数据库实例对象进行解锁操作  
  50.             }  
  51.             mDatabase = db;  
  52.         } else {  
  53.             if (mDatabase != null)  
  54.                 mDatabase.unlock();  
  55.             if (db != null)  
  56.                 db.close();  
  57.         }  
  58.     }  
  59. }  
[java] view plaincopy
  1. /* 
  2.  * 在getReadableDatabase()方法中，首先检查数据库是否已经实例化并处于打开状态 
  3.  * 如果满足要求直接返回数据库对象，否则试图获取一个可读写模式的数据库实例； 
  4.  *  当磁盘空间已满，再以只读模式打开数据库 
  5.  */  
  6. public synchronized SQLiteDatabase getReadableDatabase() {  
  7.     if (mDatabase != null && mDatabase.isOpen()) {  
  8.         return mDatabase;       //如果发现mDatabase存在并已打开，则直接返回该数据库对象  
  9.     }  
  10.   
  11.     if (mIsInitializing) {      //检查数据库是否正在进行初始化操作  
  12.         throw new IllegalStateException("初始化");  
  13.     }  
  14.   
  15.     try {  
  16.         /******注意！！！调用了getWritableDatabase()方法*****/  
  17.         return getWritableDatabase();//一般情况下使用getReadableDatabase得到的是getWritableDatabase的数据库对象  
  18.     } catch (SQLiteException e) {  
  19.         if (mName == null)  
  20.             throw e;   
  21.     }  
  22.   
  23.     /* 
  24.      * 使用可读写不能得到数据库对象，下面的操作只能得到对对象 
  25.      * 常见数据库已满，不能再添加数据，此时只能写，不能读 
  26.      */  
  27.     SQLiteDatabase db = null;  
  28.     try {  
  29.         mIsInitializing = true;  
  30.         String path = mContext.getDatabasePath(mName).getPath();  
  31.         db = SQLiteDatabase.openDatabase(path, mFactory, SQLiteDatabase.OPEN_READONLY);//以只读方式打开数据库  
  32.         if (db.getVersion() != mNewVersion) {   //只读数据库，不接收新版本数据库  
  33.             throw new SQLiteException("Can't upgrade read-only database from version " + db.getVersion() + " to "  
  34.                     + mNewVersion + ": " + path);  
  35.         }  
  36.         onOpen(db);  
  37.         Log.w(TAG, "Opened " + mName + " in read-only mode");  
  38.         mDatabase = db;                         //mDatabase为打开的数据库对象  
  39.         return mDatabase;  
  40.     } finally {  
  41.         mIsInitializing = false;  
  42.         if (db != null && db != mDatabase)  
  43.             db.close();  
  44.     }  
  45. }  

4.Cursor对象

(1).主要方法

[java] view plaincopy
  1. c.move(int offset);                 //以当前位置为参考,移动到指定行  
  2. c.moveToFirst();                //移动到第一行  
  3. c.moveToLast();                     //移动到最后一行  
  4. c.moveToPosition(int position); //移动到指定行  
  5. c.moveToPrevious();                 //移动到前一行  
  6. c.moveToNext();                 //移动到下一行  
  7. c.isFirst();                        //是否指向第一条  
  8. c.isLast();                     //是否指向最后一条  
  9. c.isBeforeFirst();                  //是否指向第一条之前  
  10. c.isAfterLast();                //是否指向最后一条之后  
  11. c.isNull(int columnIndex);          //指定列是否为空(列基数为0)  
  12. c.isClosed();                   //游标是否已关闭  
  13. c.getCount();                       //总数据项数  
  14. c.getPosition();                //返回当前游标所指向的行数  
  15. c.getColumnIndex(String columnName);//返回某列名对应的列索引值  
  16. c.getString(int columnIndex);   //返回当前行指定列的值  

(2).Cursor对象的管理

Activity提供了LoaderManager去管理cursor的生命周期，可参考cursor管理>>

(3).Cursor注意情况

1).要求

需要注意的是，在cursor的结果集中必须要包含一个“_id”的列，否则SimpleCursorAdapter会不识别，因为这源于SQLite的规范，主键以“_id”为标准。

2).措施

第一，建表时根据规范去做；
第二，查询时用别名，例如：SELECT id AS _id FROM person；
第三，使用CursorWrapper

[java] view plaincopy
  1. CursorWrapper cursorWrapper = new CursorWrapper(c) {  
  2.     @Override  
  3.     public int getColumnIndexOrThrow(String columnName) throws IllegalArgumentException {  
  4.         if (columnName.equals("_id")) {  
  5.             return super.getColumnIndex("id");  
  6.         }  
  7.         return super.getColumnIndexOrThrow(columnName);  
  8.     }  
  9. }  

5.防止数据重复插入

[java] view plaincopy
  1. @Override  
  2. public void onCreate(SQLiteDatabase db) {  
  3.     String sql = "create table bitmap(" +  
  4.             "_id integer primary key autoincrement," +  
  5.             /* 
  6.              * 防止重复,如果发现重复，数据不能添加 
  7.              * fileName varchar(100) UNIQUE 
  8.              *  
  9.              * 如果是下面这样声明，重复冲突后，原有的数据将会被替换 
  10.              * fileName varchar(100) UNIQUE ON CONFLICT REPLACE 
  11.              */  
  12.             " fileName varchar(100) UNIQUE," +    
  13.             " latitude varchar(100)," +  
  14.             " longitude varchar(100)," +  
  15.             " addr varchar(100)," +  
  16.             " isSaved integer,"+  
  17.             " model varchar(100))";  
  18.     db.execSQL(sql);  
  19. }  

6.事务Transacation

[java] view plaincopy
  1. //数据库事务  
  2. public void dbTransacation() {  
  3.     db.beginTransaction();              //开始事务  
  4.     try {  
  5.         {  
  6.             //多个sql执行语句  
  7.         }  
  8.         db.setTransactionSuccessful();  //设置事务成功完成，将缓冲区的数据提交  
  9.     } finally {  
  10.         db.endTransaction();            //结束事务  
  11.     }  
  12. }  

7.关于CursorIndexOutOfBoundsException

在使用SQLiteDatabase.openOrCreateDatabase()去打开一个sdcard上的db文件时，此时光标应该移动为记录的最后，如果没有使用cursor.moveToFirst()，就会报该异常，所有任何游标使用时，应该先moveToFirst()

[java] view plaincopy
  1. if (cursor != null && cursor.getCount() > 0) {  
  2.     cursor.moveToFirst();  
  3.     int indexTrainsetType = cursor.getColumnIndex(TrainsetTypeMetaDate.trainsetType);  
  4.     do {  
  5.         String trainsetType = cursor.getString(indexTrainsetType);  
  6.         list.add(trainsetType);  
  7.     } while (cursor.moveToNext());  
  8. }  

8.SQLITE分页查询

[java] view plaincopy
  1. //方法一：select * from table_name where id > 7 limit 10 offset 3;  
  2. limit 10 offset 3;//limit N表示取N个记录, offset P表示跳过P行.  
  3.   
  4. //方法二：select * from table_name where id > 7 limit 3,10;  
  5. limit 3,10;//limit index,count表示跳过index行后，取出count个记录  

9.Update or Replace

<code style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; white-space: inherit; background-color: rgb(255, 255, 255);"><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">INSERT</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">OR</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> REPLACE </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">INTO</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> Employee </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">(</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">id</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> name</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> role</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">)</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> 
  </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">VALUES</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(128, 0, 0); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">1</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="str" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(128, 0, 0); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">'John Foo'</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="str" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(128, 0, 0); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">'CEO'</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">);</span></code>

BAD: This will insert or replace 2 of the columns... the NAME column will be set to NULL or the default value:

<code style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; white-space: inherit; background-color: rgb(255, 255, 255);"><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">INSERT</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">OR</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> REPLACE </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">INTO</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> Employee </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">(</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">id</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> role</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">)</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> 
  </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">VALUES</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(128, 0, 0); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">1</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="str" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(128, 0, 0); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">'code monkey'</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">);</span></code>

GOOD: This will update 2 of the columns. When ID=1 exists, the NAME will be unaffected. When ID=1 does not exist, the name will be default (NULL).

<code style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; white-space: inherit; background-color: rgb(255, 255, 255);"><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">INSERT</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">OR</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> REPLACE </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">INTO</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> Employee </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">(</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">id</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> role</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> name</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">)</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> 
  </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">VALUES</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">(</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">  </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(128, 0, 0); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">1</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> 
            </span><span class="str" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(128, 0, 0); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">'code monkey'</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">
            </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">(</span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">SELECT</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> name </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">FROM</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> Employee </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">WHERE</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> id </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">=</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(128, 0, 0); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">1</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">)</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">
          </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">);</span></code>

This will update 2 of the columns. When ID=1 exists, the ROLE will be unaffected. When ID=1 does not exist, the role will be set to 'Benchwarmer' instead of the default value.

<code style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; white-space: inherit; background-color: rgb(255, 255, 255);"><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">INSERT</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">OR</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> REPLACE </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">INTO</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> Employee </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">(</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">id</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> name</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> role</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">)</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> 
  </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">VALUES</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">(</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">  </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(128, 0, 0); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">1</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> 
            </span><span class="str" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(128, 0, 0); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">'Susan Bar'</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">
            </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">COALESCE</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">((</span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">SELECT</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> role </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">FROM</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> Employee </span><span class="kwd" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(0, 0, 139); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">WHERE</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> id </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">=</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(128, 0, 0); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">1</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">),</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"> </span><span class="str" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; color: rgb(128, 0, 0); background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">'Benchwarmer'</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">)</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">
          </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;">);</span></code>

10.Replace部分字符串

You can use the built in replace() function to perform a string replace in a query.

Other string manipulation functions (and more) are detailed in the SQLite core functions list

The following should point you in the right direction.

UPDATE table SET field = replace( field, 'C:\afolder\', 'C:\anewfolder\' ) WHERE field LIKE 'C:\afolder\%'

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