錯誤選擇內部計數

Question

我有這個程序

SELECT COUNT( a.id_badania ) AS iloscBadan, COUNT( b.zdjecie ) AS iloscZdjec, COUNT (SELECT id_badania FROM Badania WHERE status='W trakcie realizacji';)
FROM Badania a
INNER JOIN Zdjecia b ON a.id_badania = b.id_badania

而這個錯誤

您的SQL語法有誤； 在第1行的“ SELECT id_badania FROM Badania WHERE status ='W trakcie realizacji'）FROM Badani”中檢查與您的MySQL服務器版本相對應的手冊以使用正確的語法

我不太了解sql。

Answer 1

您可以使用帶有case語句的sum來計算特定狀態的值

    SELECT COUNT( a.id_badania )   AS iloscBadan, COUNT( b.zdjecie ) AS iloscZdjec, Sum( case when status='W trakcie realizacji' then 1 else 0 end ) 
     FROM Badania a
     INNER JOIN Zdjecia b ON a.id_badania = b.id_badania

Answer 2

您不能將子查詢放在聚合函數中。 並且在查詢中間有一個分號。 我猜想您只需要條件聚合。 可以這樣：

SELECT COUNT( a.id_badania ) AS iloscBadan, COUNT( b.zdjecie ) AS iloscZdjec,
       SUM(status = 'W trakcie realizacji')
FROM Badania a INNER JOIN
     Zdjecia b
     ON a.id_badania = b.id_badania;

要么：

SELECT COUNT( a.id_badania ) AS iloscBadan, COUNT( b.zdjecie ) AS iloscZdjec,
       COUNT(DISTINCT case when status = 'W trakcie realizacji' then a.id_badania end)
FROM Badania a INNER JOIN
     Zdjecia b
     ON a.id_badania = b.id_badania;