Question

我读到在MySql查询中使用IN导致性能下降，这与Oracle不同，应该使用JOIN代替。我能够转换简单的查询，但我正在努力处理包含嵌套SELECT的更复杂的查询。例如：

update Records set ActiveStatus=0, TransactionStatus=0, LastUpdated=& 
where ActiveStatus!=5 and LastUpdated!=& 
and Pk in (select RecordPk from GroupRecordLink 
where GroupPk in (select Pk from Groups where ActiveStatus!=5 and 
DateTimeStamp>&))

我按照this post 进行了重写，但我不确定我的结果是否正确。

update Records r join (select distinct RecordPk from GroupRecordLink grl join 
Groups g on grl.Pk = g.Pk where g.ActiveStatus!=5 and g.DateTimeStamp>&) s
using (Pk) set ActiveStatus=0, TransactionStatus=0, LastUpdated=&  
where ActiveStatus!=5 and DateTimeStamp>&

由于

Answer 1

在Mysql中，您可以使用显式联接进行更新（您必须更改＆amp;以及正确的值）

    update Records 
    INNER JOIN GroupRecordLink on GroupRecordLink.RecordPk = Records.PK
    INNER JOIN Groups on ( GroupRecordLink.GroupPk = Groups.Pk 
                  and  Groups.ActiveStatus!=5
                         and Groups.DateTimeStamp>&)
    set ActiveStatus=0, 
    TransactionStatus=0, 
    LastUpdated=&

Answer 2

试试这个：

UPDATE Records 
INNER JOIN GroupRecordLink ON Records.Pk = GroupRecordLink.RecordPk 
INNER JOIN Groups ON GroupRecordLink.GroupPk = Groups.Pk AND Groups.ActiveStatus != 5 
SET Records.ActiveStatus = 0, 
    Records.TransactionStatus = 0, 
    Records.LastUpdated = & 
WHERE Records.ActiveStatus != 5 
  AND Records.LastUpdated != &;

MySql将嵌套的SELECT IN查询转换为JOIN

2 个答案: