Question

（您可以理解更好的阅读here）

我想知道是否可以优化此查询：

SELECT id_type, value FROM Action, Action_set WHERE id_action = id_action_p1 AND id_action_set = 1
UNION ALL
SELECT id_type, value FROM Action, Action_set WHERE id_action = id_action_p2 AND id_action_set = 1
UNION ALL
SELECT id_type, value FROM Action, Action_set WHERE id_action = id_action_p3 AND id_action_set = 1
UNION ALL
SELECT id_type, value FROM Action, Action_set WHERE id_action = id_action_p4 AND id_action_set = 1
UNION ALL
SELECT id_type, value FROM Action, Action_set WHERE id_action = id_action_p5 AND id_action_set = 1
UNION ALL
SELECT id_type, value FROM Action, Action_set WHERE id_action = id_action_p6 AND id_action_set = 1
UNION ALL
SELECT id_type, value FROM Action, Action_set WHERE id_action = id_action_p7 AND id_action_set = 1
UNION ALL
SELECT id_type, value FROM Action, Action_set WHERE id_action = id_action_p8 AND id_action_set = 1

Answer 1

尝试：

SELECT id_type, value 
FROM Action, Action_set 
WHERE id_action IN (id_action_p1,id_action_p2,id_action_p3,id_action_p4,id_action_p5,id_action_p6,id_action_p7,id_action_p8) 
AND id_action_set = 1

如果有多行，请尝试：

SELECT id_type, value 
FROM Action, Action_set 
WHERE (id_action = id_action_p1
     OR id_action = id_action_p2
     OR id_action = id_action_p3
     OR id_action = id_action_p4
     OR id_action = id_action_p5
     OR id_action = id_action_p6
     OR id_action = id_action_p7
     OR id_action = id_action_p8) 
AND id_action_set = 1

Answer 2

行;首先，您的查询没有达到预期的效果。假设您的一个动作有3个动作集; id_action_p1，id_action_p2和id_action_p3。这意味着它会在Union All查询中显示3个不同的项目，但具有相同的值 - 因为id_type和值都不取决于id_action。

如果是这样的话，你不能只使用或 - 它只会匹配一次 - 但你不止一次地回复物品而无法区分它们，这看起来很奇怪。如果是这样的话，我们可以通过在表格中包含项目列表并加入它来简化它。

首先，我们设置表格：

Select into Table_name id_action_p1 as action
Insert into Table_name (Select id_action_p2)
Insert into Table_name (Select id_action_p3)
Insert into Table_name (Select id_action_p4)
Insert into Table_name (Select id_action_p5)
...

接下来，我们编写新查询：

SELECT id_type, value 
FROM Action, Action_set, Table_name 
WHERE id_action=Table_name.action
AND id_action_set = 1

这应该与您之前的查询完全相同。

是否可以优化我的查询？

2 个答案: