Question

我想寫一個postgres查詢，這是與CASE語句。查詢如下：

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 

請告知：

在 'State' = 'State'

然而，當我執行下面的查詢，我得到相應的結果

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 

以上查詢顯示語法錯誤我知道我做錯了什麼。

編輯：

THEN子句後的值是動態的，它可含有1倍或更多的值（從多選擇框）。我想查詢被執行爲

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 

哪個運行得很好，但問題是CASE沒有返回我所需的字符串。

Answer 1

您的查詢應該是這樣的，我希望這會爲你工作

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

你不能有多個值的單個案例。

那問題

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

Answer 3

既然你試圖使用IN，您可以利用的事實上，IN接受集合或一個數組：

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的重新語句，將IN測試推入CASE語句。

Answer 4

'State'='State'是一個重言式。 您的意思是「State」='State'，即列「State」的值等於字符串'State'？