android 数据库操作

定义schema:

 1 public final class FeedReaderContract {

 2     // To prevent someone from accidentally instantiating the contract class,

 3     // give it an empty constructor.

 4     public FeedReaderContract() {}

 5 

 6     /* Inner class that defines the table contents */

 7     public static abstract class FeedEntry implements BaseColumns {

 8         public static final String TABLE_NAME = "entry";

 9         public static final String COLUMN_NAME_ENTRY_ID = "entryid";

10         public static final String COLUMN_NAME_TITLE = "title";

11         public static final String COLUMN_NAME_SUBTITLE = "subtitle";

12         ...

13     }

14 }

自定义SQL Helper:

 1 public class FeedReaderDbHelper extends SQLiteOpenHelper {

 2     // If you change the database schema, you must increment the database version.

 3     public static final int DATABASE_VERSION = 1;

 4     public static final String DATABASE_NAME = "FeedReader.db";

 5 

 6    private static final String TEXT_TYPE = " TEXT";

 7    private static final String COMMA_SEP = ",";

 8    private static final String SQL_CREATE_ENTRIES =

 9     "CREATE TABLE " + FeedEntry.TABLE_NAME + " (" +

10     FeedEntry._ID + " INTEGER PRIMARY KEY," +

11     FeedEntry.COLUMN_NAME_ENTRY_ID + TEXT_TYPE + COMMA_SEP +

12     FeedEntry.COLUMN_NAME_TITLE + TEXT_TYPE + COMMA_SEP +

13     ... // Any other options for the CREATE command

14     " )";

15 

16 private static final String SQL_DELETE_ENTRIES =

17     "DROP TABLE IF EXISTS " + FeedEntry.TABLE_NAME;

18 

19 

20     public FeedReaderDbHelper(Context context) {

21         super(context, DATABASE_NAME, null, DATABASE_VERSION);

22     }

23     public void onCreate(SQLiteDatabase db) {

24         db.execSQL(SQL_CREATE_ENTRIES);

25     }

26     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

27         // This database is only a cache for online data, so its upgrade policy is

28         // to simply to discard the data and start over

29         db.execSQL(SQL_DELETE_ENTRIES);

30         onCreate(db);

31     }

32     public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {

33         onUpgrade(db, oldVersion, newVersion);

34     }

35 }

View Code

插入条目：

 1 FeedReaderDbHelper mDbHelper = new FeedReaderDbHelper(getContext());

 2 

 3 // Gets the data repository in write mode

 4 SQLiteDatabase db = mDbHelper.getWritableDatabase();

 5 

 6 // Create a new map of values, where column names are the keys

 7 ContentValues values = new ContentValues();

 8 values.put(FeedEntry.COLUMN_NAME_ENTRY_ID, id);

 9 values.put(FeedEntry.COLUMN_NAME_TITLE, title);

10 values.put(FeedEntry.COLUMN_NAME_CONTENT, content);

11 

12 // Insert the new row, returning the primary key value of the new row

13 long newRowId;

14 newRowId = db.insert(

15          FeedEntry.TABLE_NAME,

16          FeedEntry.COLUMN_NAME_NULLABLE,

17          values);

View Code

查找、更新、删除：

 1 SQLiteDatabase db = mDbHelper.getReadableDatabase();

 2 

 3 // Define a projection that specifies which columns from the database

 4 // you will actually use after this query.

 5 String[] projection = {

 6     FeedEntry._ID,

 7     FeedEntry.COLUMN_NAME_TITLE,

 8     FeedEntry.COLUMN_NAME_UPDATED,

 9     ...

10     };

11 

12 // How you want the results sorted in the resulting Cursor

13 String sortOrder =

14     FeedEntry.COLUMN_NAME_UPDATED + " DESC";

15 

16 Cursor c = db.query(

17     FeedEntry.TABLE_NAME,  // The table to query

18     projection,                               // The columns to return

19     selection,                                // The columns for the WHERE clause

20     selectionArgs,                            // The values for the WHERE clause

21     null,                                     // don't group the rows

22     null,                                     // don't filter by row groups

23     sortOrder                                 // The sort order

24     );

View Code

 1 SQLiteDatabase db = mDbHelper.getReadableDatabase();

 2 

 3 // Define a projection that specifies which columns from the database

 4 // you will actually use after this query.

 5 String[] projection = {

 6     FeedEntry._ID,

 7     FeedEntry.COLUMN_NAME_TITLE,

 8     FeedEntry.COLUMN_NAME_UPDATED,

 9     ...

10     };

11 

12 // How you want the results sorted in the resulting Cursor

13 String sortOrder =

14     FeedEntry.COLUMN_NAME_UPDATED + " DESC";

15 

16 Cursor c = db.query(

17     FeedEntry.TABLE_NAME,  // The table to query

18     projection,                               // The columns to return

19     selection,                                // The columns for the WHERE clause

20     selectionArgs,                            // The values for the WHERE clause

21     null,                                     // don't group the rows

22     null,                                     // don't filter by row groups

23     sortOrder                                 // The sort order

24     );

View Code

// Define 'where' part of query.

String selection = FeedEntry.COLUMN_NAME_ENTRY_ID + " LIKE ?";

// Specify arguments in placeholder order.

String[] selectionArgs = { String.valueOf(rowId) };

// Issue SQL statement.

db.delete(table_name, selection, selectionArgs);

SQLiteDatabase db = mDbHelper.getReadableDatabase();



// New value for one column

ContentValues values = new ContentValues();

values.put(FeedEntry.COLUMN_NAME_TITLE, title);



// Which row to update, based on the ID

String selection = FeedEntry.COLUMN_NAME_ENTRY_ID + " LIKE ?";

String[] selectionArgs = { String.valueOf(rowId) };



int count = db.update(

    FeedReaderDbHelper.FeedEntry.TABLE_NAME,

    values,

    selection,

    selectionArgs);

 

 

访问数据库数据：

cursor.moveToFirst();

long itemId = cursor.getLong(

    cursor.getColumnIndexOrThrow(FeedEntry._ID)

);