SELECT 和 VIEW 中的 SELECT 结果不同答案

【问题标题】：different result from SELECT and from SELECT inside a VIEWSELECT 和 VIEW 中的 SELECT 结果不同
【发布时间】：2011-06-04 15:42:58
【问题描述】：

SELECT 语句的结果与 VIEW 中的 SELECT 的结果不同。如何解决问题并在视图中获得相同的结果？

动作表：

+--+---------+--------------+-----------+------+
|id|person_id|action_type_id|currency_id|sum   |
+--+---------+--------------+-----------+------+
|1 |1        |1             |1          | 1.00 |
|2 |1        |1             |1          | 5.00 |
|3 |1        |1             |2          |10.00 | 
|4 |1        |2             |1          | 2.00 |
|5 |2        |1             |1          |20.00 |
|6 |2        |2             |2          | 5.00 |
+--+---------+--------------+-----------+------+

选择：

SELECT person_id AS p, currency_id AS c,
(
CAST(
COALESCE(
(SELECT SUM(sum) FROM actions WHERE action_type_id=1 AND person_id=p AND currency_id=c)
, 0)
AS DECIMAL(11,2)) -
CAST(
COALESCE(
(SELECT SUM(sum) FROM actions WHERE action_type_id=2 AND person_id=p AND currency_id=c)
, 0)
AS DECIMAL(11,2))
) AS sum
FROM actions
GROUP BY currency_id, person_id
ORDER BY person_id, currency_id;

结果：

+--+--+------+
|p |c |sum   |
+--+--+------+
|1 |1 | 4.00 |
|1 |2 |10.00 |
|2 |1 |20.00 |
|2 |2 |-5.00 |
+--+--+------+

选择内部视图：

CREATE VIEW p_sums AS
SELECT person_id AS p, currency_id AS c,
(
CAST(
COALESCE(
(SELECT SUM(sum) FROM actions WHERE action_type_id=1 AND person_id=p AND currency_id=c)
, 0)
AS DECIMAL(11,2)) -
CAST(
COALESCE(
(SELECT SUM(sum) FROM actions WHERE action_type_id=2 AND person_id=p AND currency_id=c)
, 0)
AS DECIMAL(11,2))
) AS sum
FROM actions
GROUP BY currency_id, person_id
ORDER BY person_id, currency_id;

SELECT * FROM p_sums;

结果：

+--+--+------+
|p |c |sum   |
+--+--+------+
|1 |1 |29.00 |
|1 |2 |29.00 |
|2 |1 |29.00 |
|2 |2 |29.00 |
+--+--+------+

【问题讨论】：

你用的是什么版本的mysql？
仅供参考，对于新手（我也是一个），当有人帮助提供解决方案时，它可以让您超越您的树桩，请点击他们回答下方的复选框给予他们信任，以便其他人知道解决方案已经解决。
我这样做了，但是我要等 60 秒才能接受答案:)

标签： sql mysql sql-view

【解决方案1】：

你可以不做吗：

SELECT person_id AS p, currency_id AS c, SUM(CASE action_Type_id WHEN 1 THEN sum WHEN 2 THEN -sum END) as sum
FROM actions
GROUP BY currency_id, person_id
ORDER BY person_id, currency_id;

即摆脱子查询，只建立一个总结（使 action_type_id 2 值为负）

【讨论】：

它有效！它非常优雅。非常非常感谢！！