Question

我想在sum的行中获取sqlite个类似项目。

例如， x 的所有值， y 的所有值以及 z 的所有值。我知道如何在我的查询中使用WHERE子句，但问题是它需要我将值与另一个参数进行比较。例如，像这样的查询：

select sum(number_column) from your_table where number_column = 'some_number'

从上面来看，我没有'some_number'来比较。所以我需要一种方法来为每个相似的行添加所有值，有点像将它们组合在一起。

所以我最终会得到类似的东西：

x 25
y 24
z 16

这可能吗？欢迎任何建议。

编辑：在克里斯蒂安的建议之后我尝试了这个：

＆＃13;

 private void getSumOfGroupedTime() {
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor c = db.rawQuery("SELECT " + KEY_CREATED_AT_AM_PM + ",sum(quantity) as sum FROM " + TABLE_SALES
                + " GROUP BY " + KEY_CREATED_AT_AM_PM, null);
        c.moveToFirst();
        double i = c.getDouble(0);
        Log.d("sum_values_", String.valueOf(i));
        c.close();
    }
But it returns 1 for the three similar items i added in which each of these items have 1 as quantity. I expected 3. I'm i doing it wrong?

＆＃13;

Answer 1

假设您有一个具有以下结构的表：

+----------------+--------+
| KEY_CREATED_AT | number |
+----------------+--------+
| a              |    132 |
| e              |    264 |
| f              |    142 |
| x              |    132 |
| y              |    122 |
| z              |    112 |
+----------------+--------+

为了获得这些单独值的总和，您可以使用group by

子句

所以查询将是这样的：

SELECT KEY_CREATED_AT,sum(number) as sum FROM table_name

GROUP BY KEY_CREATED_AT

此处示例：sqlfiddle

private void getSumOfGroupedTime() {
   SQLiteDatabase db = this.getReadableDatabase();
   Cursor c = db.rawQuery("SELECT " + KEY_CREATED_AT_AM_PM + ",sum(quantity) as sum FROM " + TABLE_SALES
            + " GROUP BY " + KEY_CREATED_AT_AM_PM, null);
   try {
        while (c.moveToNext()) {
            Double sum = c.getDouble(1);

            Log.d("Sum is: " + sum);
        }
   } finally {
      c.close();
   }

}

sqlite数据库中给定列的数字总和

1 个答案: