Android: How can I port ExecuteScalar to Java?

Question

SqlCommand.ExecuteScalar Method
Executes the query, and returns the first column of the first row in the result set returned by the query. Additional columns or rows are ignored.

I guess this will involve heavy use of generics.

Assume I have an SQLiteDatabase / Cursor object.

Answer 1

Have a look at SQLLiteStatement

long simpleQueryForLong() Execute a statement that returns a 1 by 1 table with a numeric value.

String simpleQueryForString() Execute a statement that returns a 1 by 1 table with a text value.

Answer 2

This logic worked for me:

public int ExecuteScalar(/* code...*/) {
    Cursor cursor = database.rawQuery(sql, selectionArgs);
    try {
        cursor.moveToNext();
        int val = cursor.getInt(0);
        cursor.close();
        return val;
    }   
    catch (Exception e) {
        /* code...*/
    }
    return -1;
}

Answer 3

给数据库对象是db

long result = db.compileStatement("select count(*) from some_table").simpleQueryForLong();

Answer 4

如果要检索主键，则可以使用语句getGeneratedKeys方法，该方法在插入后返回生成键的resultSet。