postgresql - Postgres案例查询问题

Question

我正在尝试编写一个带有 CASE 语句的 postgres 查询。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','State 2','State 3'
        WHEN 'State' = 'District' THEN 'State 1'
    END) 
  group by x ORDER BY x,y 

上面的查询在 'State' = 'State' 处显示语法错误

然而，当我执行以下查询时，我得到了适当的结果:

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

请让我知道我做错了什么。

编辑:

THEN 子句后的值是动态的，它可能包含 1 个或多个值(来自多选框)。我希望查询执行为

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 

运行得很好，但问题是 CASE 没有返回我需要的字符串。

Answer 1

你的查询应该是这样的，我希望这对你有用

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