你能用两个带连接的嵌入式选择来改进mysql更新吗？

Question

我在此查询中使用了3个表：

1. 讲师（包含＆＃34;软＆＃34;已删除的专栏）
2. school（包含＆＃34; soft＆＃34;已删除的专栏）
3. instructor_school（讲师和学校之间的关联表）

如果学校被标记为已删除，我希望该学校的教师也被标记为已删除，但仅 。这是我提出的查询：

Function test_zeroSQL()

Dim nsemaine As Single
Dim var11 As Single
Dim var50 As Single
Dim var60 As Single
Dim var11b As Single
Dim var50b As Single
Dim var60b As Single

nsemaine = DatePart("ww", Date, 2, 2) - 1
If zero11() = 0 Then
    var11 = 1
    var11b = 1
Else
    var11 = zero11()
    var11b = zero11b()
End If

If zero50() = 0 Then
    var50 = 1
    var50b = 1
Else
    var50 = zero50()
    var50b = zero50b()
End If

If zero60() = 0 Then
    var60 = 1
    var60b = 1
Else
    var60 = zero60()
    var60b = zero60b()
End If

test_zeroSQL = "INSERT INTO [Taux de Service] ( Semaine, [Sortie B60], [Nc B60], [Sortie B50], [Nc B50], [Sortie B11], [Nc B11] )"
test_zeroSQL = test_zeroSQL & vbCrLf & "VALUES (" & nsemaine & "," & var60 & "," & var60b & "," & var50 & "," & var50b & "," & var11 & " ," & var11b & " )"
End Function

如果我们只允许每个教师在一所学校，那么查询会更简单：

update instructor as i
set deleted=1
where
(select count(*) from instructor_school as i_s join school s
 on s.id=i_s.school_id
 where i_s.instructor_id=i.id) = 
(select count(*) from instructor_school as i_s join school s
 on s.id=i_s.school_id
 where i_s.instructor_id=i.id and s.deleted=1);

我的问题是 - 此查询是解决此问题的最佳方法 - 或者您能建议更好的查询吗？

感谢您的任何建议！

Answer 1

UPDATE instructor AS i
JOIN instructor_school i_s_deleted ON i.id = i_s_deleted.instructor_id
JOIN school s_deleted ON i_s_deleted.school_id = s_deleted.id AND s_deleted.deleted = 1
LEFT JOIN instructor_school AS i_s_active 
    JOIN school s_active ON i_s_active.school_id = s_active.id AND s_active.deleted <> 1
ON i.id = i_s_active.instructor_id 
SET i.deleted=1
WHERE i_s_active.school_id IS NULL;

我在这里所做的是首先我加入了instructor_school和学校，以确保有一所学校被删除。然后我再次加入了instructor_school和学校作为活动，然后我把i_s_active.school_id为null放在我的where子句中。这将确保教师不与任何活跃的学校相关联。

希望这有帮助！