SQLite数据库查询

Question

I have three columns in my database id ,message and message status and I only want to select only those rows from the list whose message status is 'r' and want to return the cursor from query for only id and message. I am new to databases,Please help. My current code which is selecting all the rows is:

private String[] allColumns = { MySQLiteHelper.COLUMN_ID,MySQLiteHelper.COLUMN_MESSAGE };

public List<Message> getAllMessages() {
    List<Message> message = new ArrayList<Message>();

    Cursor cursor = database.query(MySQLiteHelper.TABLE_NAME,allColumns, null, null, null, null, null);

    cursor.moveToFirst();
    while (!cursor.isAfterLast()) {
      Message message1 = cursorToMessage(cursor);
      message.add(message1);
      cursor.moveToNext();
    }
    // Make sure to close the cursor
    cursor.close();
    return message;
  }

Answer 1

You need to pass a Where clause yo your query. It is the 4th parameter of the query() . It takes a String , and you should not include the Sqlite3 keyword WHERE (Android does that for you). The clause can be structured like MySQLiteHelper.COLUMN_MESSAGE+"="+"r"

Answer 2

 SQLiteDatabase database = this.getReadableDatabase();
 String queryz = "SELECT " + COLUMN_ID + "," + COLUMN_MESSAGE + " FROM " + TABLE_NAME + " WHERE " + COLUMN_MESSAGE_STATUS + "= 'r'";
 Cursor c = database.rawQuery(queryz, null);

Answer 3

Try this code,

public static final String KEY_ROWID = "row";
public static final String KEY_NAME = "name";

public Cursor fetchNamesByConstraint(String filter) {
    Cursor cursor = mDb.query(true, DATABASE_NAMES_TABLE, null, "row LIKE '%" + filter + "%' or name LIKE '%" + filter + "%'",null, null, null, null);
}