Question

为什么我收到此错误？

 SELECT        unitCode
        FROM            Enrolment
        WHERE        count(studentID) >
         (SELECT        AVG(Students) AS avgstudents
        FROM            (SELECT        COUNT(*) AS Students
       FROM            Enrolment AS Enrolment_1
        GROUP BY unitCode) AS a))

Answer 1

看起来最后有一个额外的paren。我不太了解SQL，所以我不能说是否有任何错误（或者paren是否是一个问题）。

Answer 2

在where子句中，我们不能使用聚合函数。您可以在HAVING子句中使用count（studentID）函数。

检查此样本，

SELECT department, SUM(sales) as "Total sales"
FROM order_details
GROUP BY department
HAVING SUM(sales) > 1000;

Answer 3

大卫检查一下，

select count(*),unicode from Enrolement 
    having count(StudentID) > (select avg(Students) ad avgstudents,unitCode
    from table_Name where Enrolement = "some of ur condtion"
    group by unitCode)

需要更改格式化语法的查询..相应地检查您的查询业务。

Answer 4

试试这个：

select unitCode
from Enrolment
group by unitCode
having count(*) > (select avg(c.c) from (select count(*) as c from Enrolment group by unitCode) c);

适当尊重：

TSQL: Cannot perform an aggregate function AVG on COUNT(*) to find busiest hours of day

子查询有子句错误，我错过了什么？

4 个答案: