android - SQLiteDatabase 在查询中需要帮助...请

Question

我有这张表:

id | CUPNAME | FRENCHNAME
1  | 2       | null
2  | null    | 4

我想从非空的 CUPNAME 和 FRENCHNAME 中提取数据。表格可以填1到10的数字。在这个例子中，应该可以CUPNAME=2，FRENCHNAME=4。

有这样一个查询:

SELECT sum(ifnull(french_press_bd.CUPNAME,0)) as a , sum(ifnull(french_press_bd.FRENCHNAME,0)) as b FROM my_table WHERE id in (1,2)

我试着写，所以它不起作用:

 String sqr = "id in (1,2)";
Cursor cursor = sqdb.query(french_press_bd.TABLE_NAME, new String[] {                   
"sum(ifnull(french_press_bd.CUPNAME,0)) as a , sum(ifnull(french_press_bd.FRENCHNAME,0)) as b" 
},sqr, null,null,null,null );

Answer 1

我认为您可以使用 rawQuery。作为:

String your_query= "SELECT sum(ifnull(french_press_bd.CUPNAME,0)) as a , sum(ifnull(french_press_bd.FRENCHNAME,0)) as b FROM my_table WHERE id in (1,2)";
Cursor result = sqdb.rawQuery(your_query, null);

但要确保 SQLiteDatabase 不是 NULL。你必须在它之前打电话，

sqdb = dbhelper.getReadableDatabase(); // or getWritableDatabase()