mysql - 错误-选择内部计数

Question

我有这个程序

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

还有这个错误

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SELECT id_badania FROM Badania WHERE status='W trakcie realizacji') FROM Badani' at line 1

我不太了解sql。

Answer 1

您可以使用带有 case 语句的 sum 来计算特定状态的值

    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