为什么我从这个子查询脚本中得到一个错误？

Question

我遇到与子查询有关的问题，并从其他表离开。

代码：

SELECT effectiveDate,

    (SELECT

      CASE
        WHEN note='REGULAR LOGGED' THEN log
      END

    FROM schedules LEFT JOIN timesheet ON schedules.effectiveDate = timesheet.date WHERE schedules.empid='40'
    AND YEAR(effectiveDate) = YEAR(CURDATE()) AND MONTH(effectiveDate) ='1' GROUP BY effectiveDate

    )

    FROM schedules
    LEFT JOIN timesheet ON schedules.effectiveDate = timesheet.date WHERE schedules.empid='40'
    AND YEAR(effectiveDate) = YEAR(CURDATE()) AND MONTH(effectiveDate) ='1' GROUP BY effectiveDate

Answer 1

这就是你的实际查询

 SELECT effectiveDate,
 CASE
        WHEN note='REGULAR LOGGED' THEN log
      END
     FROM schedules LEFT JOIN timesheet ON schedules.effectiveDate = timesheet.date WHERE schedules.empid='40'
    AND YEAR(effectiveDate) = YEAR(CURDATE()) AND MONTH(effectiveDate) ='1' GROUP BY effectiveDate.

不知道为什么要使用子查询