sqlite 基本操作

Android SQLite数据库操作实例

博客分类：  android

 

     Android的自带数据库SQLite小巧且功能强大，Android提供了两种方式去操作数据库，第一种是用SQL语句去操作数据，SQLite支持标准的SQL，其分页等操作与Mysql一样，以下是利用SQL操作SQLite：

 import java.util.ArrayList;
 import java.util.List;

 import android.content.Context;
 import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;

 public class PersonDaoClassic {
     private DBOpenHelper helper;

     public PersonDaoClassic(Context context) {
         helper = new DBOpenHelper(context);
     }

     public void insert(Person p) {
         // 打开可写数据库
         SQLiteDatabase db = helper.getWritableDatabase();

         // 执行SQL语句, 替换占位符
         db.execSQL("INSERT INTO person(name, balance) VALUES(?, ?)", new Object[] { p.getName(), p.getBalance() });

         // 释放资源
         db.close();
     }

     public void delete(int id) {
         SQLiteDatabase db = helper.getWritableDatabase();
         db.execSQL("DELETE FROM person WHERE id=?", new Object[] { id });
         db.close();
     }

     public void update(Person p) {
         SQLiteDatabase db = helper.getWritableDatabase();
         db.execSQL("UPDATE person SET name=?, balance=? WHERE id=?", new Object[] { p.getName(), p.getBalance(), p.getId() });
         db.close();
     }

     public Person query(int id) {
         SQLiteDatabase db = helper.getReadableDatabase();

         // 执行原始查询, 得到一个Cursor(类似ResultSet)
         Cursor c = db.rawQuery("SELECT name, balance FROM person WHERE id=?", new String[] { String.valueOf(id) });
         Person p = null;

         // 判断Cursor是否有下一条记录
         if (c.moveToNext())
             // 从Cursor中获取数据, 创建Person对象
             p = new Person(id, c.getString(0), c.getInt(1));

         // 释放资源
         c.close();
         db.close();
         return p;
     }

     public List queryAll() {
         SQLiteDatabase db = helper.getReadableDatabase();
         Cursor c = db.rawQuery("SELECT id, name, balance FROM person", null);
         List persons = new ArrayList();
         while (c.moveToNext())
             persons.add(new Person(c.getInt(0), c.getString(1), c.getInt(2)));
         c.close();
         db.close();
         return persons;
     }

     public List queryPage(int pageNum, int capacity) {
         // 开始索引
         String start = String.valueOf((pageNum - 1) * capacity);
         // 查询的个数
         String length = String.valueOf(capacity);

         SQLiteDatabase db = helper.getReadableDatabase();

         // 翻页查询语句, 和MySQL中相同
         Cursor c = db.rawQuery("SELECT id, name, balance FROM person LIMIT ?,?", new String[]{start, length});
         List persons = new ArrayList();
         while (c.moveToNext())
             persons.add(new Person(c.getInt(0), c.getString(1), c.getInt(2)));
         c.close();
         db.close();
         return persons;
     }

     public int queryCount() {
         SQLiteDatabase db = helper.getReadableDatabase();

         // 查询记录条数
         Cursor c = db.rawQuery("SELECT COUNT(*) FROM person", null);
         c.moveToNext();
         int count =c.getInt(0);
         c.close();
         db.close();
         return count;
     }

 }

      除上述方法以外，android还给我们带来了另外一种更加简单，也是android推荐使用的一种方式，此种方式把数据封装在ContentValues中，因为android编程过程中经常会使用到已经封装好了数据的ContentValues，所以使用第二种方式在有些时候更加便捷，以下是代码：

 package cn.itcast.sqlite;

 import java.util.ArrayList;
 import java.util.List;

 import android.content.ContentValues;
 import android.content.Context;
 import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;

 public class PersonDao {
     private DBOpenHelper helper;

     public PersonDao(Context context) {
         helper = new DBOpenHelper(context);
     }

     public void remit(int from, int to, int amount) {
         SQLiteDatabase db = helper.getWritableDatabase();

         // 开启事务
         db.beginTransaction();
         try {
             db.execSQL("UPDATE person SET balance=balance-? WHERE id=?", new Object[]{amount, from});
             db.execSQL("UPDATE person SET balance=balance+? WHERE id=?", new Object[]{amount, to});
             db.setTransactionSuccessful();
         } catch (Exception e) {
             e.printStackTrace();
         }
         // 结束事务, 将事务成功点前面的代码提交
         db.endTransaction();

         db.close();
     }

     public void insert(Person p) {
         SQLiteDatabase db = helper.getWritableDatabase();

         // 准备数据
         ContentValues values = new ContentValues();
         values.put("name", p.getName());
         values.put("balance", p.getBalance());

         // 通过ContentValues中的数据拼接SQL语句, 执行插入操作, id为表中的一个列名
         db.insert("person", "id", values);

         db.close();
     }

     public void delete(int id) {
         SQLiteDatabase db = helper.getWritableDatabase();

         // 执行删除操作, 在person表中删除id为指定值的记录
         db.delete("person", "id=?", new String[]{String.valueOf(id)});

         db.close();
     }

     public void update(Person p) {
         SQLiteDatabase db = helper.getWritableDatabase();

         // 要更新的数据
         ContentValues values = new ContentValues();
         values.put("name", p.getName());
         values.put("balance", p.getBalance());

         // 更新person表中id为指定值的记录
         db.update("person", values, "id=?", new String[] { String.valueOf(p.getId()) });

         db.close();
     }

     public Person query(int id) {
         SQLiteDatabase db = helper.getReadableDatabase();

         // 执行查询: 不去重复, 表是person, 查询name和balance两列, Where条件是"id=?", 占位符是id, 不分组, 没有having, 不排序, 没有分页
         Cursor c = db.query(false, "person", new String[]{"name", "balance"}, "id=?", new String[]{String.valueOf(id)}, null, null, null, null);

         Person p = null;
         // 判断Cursor是否有下一条记录
         if (c.moveToNext())
             // 从Cursor中获取数据, 创建Person对象
             p = new Person(id, c.getString(0), c.getInt(1));

         // 释放资源
         c.close();
         db.close();
         return p;
     }

     public List queryAll() {
         SQLiteDatabase db = helper.getReadableDatabase();

         // 查询所有记录, 倒序
         Cursor c = db.query(false, "person", new String[]{"id","name", "balance"}, null, null, null, null, "id DESC", null);

         List persons = new ArrayList();
         while (c.moveToNext())
             persons.add(new Person(c.getInt(0), c.getString(1), c.getInt(2)));
         c.close();
         db.close();
         return persons;
     }

     public List queryPage(int pageNum, int capacity) {
         // 开始索引
         String start = String.valueOf((pageNum - 1) * capacity);
         // 查询的个数
         String length = String.valueOf(capacity);

         SQLiteDatabase db = helper.getReadableDatabase();

         // 翻页查询
         Cursor c = db.query(false, "person", new String[]{"id","name", "balance"}, null, null, null, null, null, start + "," + length);

         List persons = new ArrayList();
         while (c.moveToNext())
             persons.add(new Person(c.getInt(0), c.getString(1), c.getInt(2)));
         c.close();
         db.close();
         return persons;
     }

     public int queryCount() {
         SQLiteDatabase db = helper.getReadableDatabase();

         // 查询记录条数
         Cursor c = db.query(false, "person", new String[]{"COUNT(*)"}, null, null, null, null, null, null);

         c.moveToNext();
         int count =c.getInt(0);
         c.close();
         db.close();
         return count;
     }

 }