题
从SELECT语句的结果是由该结果从SELECT内部VIEW不同。如何解决这个问题,从视图得到同样的结果?
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 |
+--+--+------+
解决方案
你不能做的:
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,只是建立一个单一的总结(制造action_type_id 2个值负)
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