public class FeedReaderDbHelper extends SQLiteOpenHelper {

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

    public static final int DATABASE_VERSION = 1;

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

    public FeedReaderDbHelper(Context context) {

        super(context, DATABASE_NAME, null, DATABASE_VERSION);

    }

    /*(必须重写的方法)

该函数是在第一次创建数据库的时候执行，实际上是在第一次得到SQLiteDatabase对象的时候，才会调用这个方法

    * 在SQLiteOpenHelper的getReaderDatabase()或者getWritableDatabase()

    * 被第一次调用时都会调用该方法

    */

    public void onCreate(SQLiteDatabase db) {

        db.execSQL(SQL_CREATE_ENTRIES);

    }

    //(必须重写的方法)数据库更新的时候会调用该方法

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

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

        // to simply to discard the data and start over

        db.execSQL(SQL_DELETE_ENTRIES);

        onCreate(db);

    }

    //可以不用重写

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

        onUpgrade(db, oldVersion, newVersion);

    }

}

DatabaseHelper dbHelper = new DatabaseHelper(getApplicationContext());

SQLiteDatabase db = dbHelper.getWritableDatabase();

ContentValues cv = new ContentValues();

//key是列名，value是要插入的值

cv.put("name", "value");

//rowId是返回的新插入的行号，如果插入失败返回-1

long rowId = db.insert("user_table", null, cv);

SQLiteDatabase db = mDbHelper.getReadableDatabase();

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

// you will actually use after this query.

//需要查询返回的列名

String[] projection = {

    FeedEntry._ID,

    FeedEntry.COLUMN_NAME_TITLE,

    FeedEntry.COLUMN_NAME_UPDATED,

    ...

    };

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

//查询语句排序

String sortOrder =

    FeedEntry.COLUMN_NAME_UPDATED + " DESC";

Cursor c = db.query(

    FeedEntry.TABLE_NAME,  // The table to query

    projection,                               // The columns to return

    selection,                                // The columns for the WHERE clause

    selectionArgs,                            // The values for the WHERE clause

    null,                                     // don't group the rows

    null,                                     // don't filter by row groups

    sortOrder                                 // The sort order

    );

cursor.moveToFirst();

long itemId = cursor.getLong(

    cursor.getColumnIndexOrThrow(FeedEntry._ID)

);