Question

这是4张桌子......

tbl_std_working_hour
tbl_attendance
tbl_holiday
tbl_leave

我想通过此查询找出员工缺席报告....但是我需要为很多员工应用此报告...有什么方法可以简化此查询吗？

SELECT date
FROM tbl_std_working_hour
WHERE date NOT IN (SELECT date FROM tbl_attendance WHERE emp_id = '$emp_id')
AND date NOT IN (SELECT date FROM tbl_holiday)
AND date NOT IN (SELECT date FROM tbl_leave WHERE emp_id = '$emp_id')
AND total_hour <> '00:00:00'
AND date >= '$start'
AND date <= '$end'
AND emp_id = '$emp_id'

Answer 1

首先，我会使用NOT EXISTS重写：

SELECT wh.date
FROM tbl_std_working_hour wh
WHERE NOT EXISTS (SELECT 1
                  FROM tbl_attendance a
                  WHERE a.date = wh.date AND a.emp_id = wh.emp_id
                 ) AND
      NOT EXISTS (SELECT 1
                  FROM tbl_holiday h
                  WHERE h.date = wh.date
                 ) AND
      NOT EXISTS (SELECT 1
                  FROM tbl_leave l
                  WHERE l.emp_id = wh.emp_id and l.date = wh.date
                 )
WHERE wh.total_hour <> '00:00:00' AND
      wh.date >= '$start' AND
      wh.date <= '$end' AND
      wh.emp_id = '$emp_id';

然后添加以下复合（多列）索引：

tbl_std_working_hour(emp_id, date, total_hour)
tbl_attendance(emp_id, date)
tbl_holiday(date)（如果date是主键或唯一身份，则可能已存在）
tbl_leave(emp_id)（如果emp_id是主键或唯一身份，则可能已存在）

请注意，我更改了子查询以引用外部查询中的emp_id。这样可以更轻松地更改emp_id。此外，您的查询应该使用WHERE子句中的值的参数。

Answer 2

这也是使用UNION ALL

更好地工作的更好方法

SELECT date
FROM tbl_std_working_hour AS tswh
WHERE NOT EXISTS(
    SELECT date FROM tbl_attendance ta WHERE ta.date = tswh.date AND ta.emp_id = tswh.emp_id
    UNION ALL
    SELECT date FROM tbl_holiday th WHERE th.date = tswh.date
    UNION ALL
    SELECT date FROM tbl_leave tl WHERE tl.date = tswh.date AND tl.emp_id = tswh.emp_id)
AND total_hour <> '00:00:00'
AND date >= '$start'
AND date <= '$end'
AND emp_id = '$emp_id'

如何优化此SQL查询？

2 个答案: