Question

我想写一个postgres查询，这是与CASE语句。查询如下：

SELECT "State" AS x, count("Age Group") AS y from test.smp_state_survey where "State" IN 
(CASE 
     WHEN 'State' = 'State' THEN 'State 1' 
     WHEN 'State' = 'District' THEN 'State 1' 
    END) 
    group by x ORDER BY x,y 

请告知：

在 'State' = 'State'

然而，当我执行下面的查询，我得到相应的结果

SELECT "State" AS x, count("Age Group") AS y from test.smp_state_survey where "State" IN 
(CASE 
     WHEN 'State' = 'State' THEN 'State 1','State 2','State 3' 
     WHEN 'State' = 'District' THEN 'State 1' 
    END) 
    group by x ORDER BY x,y 

以上查询显示语法错误我知道我做错了什么。

编辑：

THEN子句后的值是动态的，它可含有1倍或更多的值（从多选择框）。我想查询被执行为

SELECT "State" AS x, count("Age Group") AS y from test.smp_state_survey where "State" IN 
('State 1','State 2','State 3') 
    group by x ORDER BY x,y 

哪个运行得很好，但问题是CASE没有返回我所需的字符串。

Answer 1

您的查询应该是这样的，我希望这会为你工作

SELECT "State" AS x, count("Age Group") AS y from test.smp_state_survey where 
CASE 
     WHEN 'State' = 'State' THEN "State" IN ('State 1' ,'State 3') 
     WHEN 'State' = 'District' THEN "State" IN ('District 1') 
    END 
    group by x ORDER BY x,y 

Answer 2

你不能有多个值的单个案例。

那问题

WHEN 'State' = 'State' THEN 'State 1','State 2','State 3' 

Answer 3

既然你试图使用IN，您可以利用的事实上，IN接受集合或一个数组：

SELECT "State" AS x, count("Age Group") AS y 
FROM test.smp_state_survey 
WHERE "State" IN (CASE 
    WHEN 'State' = 'State' THEN ARRAY['State 1','State 2','State 3'] 
    WHEN 'State' = 'District' THEN ARRAY['State 1'] 
END) 
GROUP BY x 
ORDER BY x,y 

或使用@ user1327246的重新语句，将IN测试推入CASE语句。

Answer 4

'State'='State'是一个重言式。 您的意思是“State”='State'，即列“State”的值等于字符串'State'？