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本文主要简述一下不同sql语句并发update的情况。
指定主键update
update tableA set owner = ? where id = ?指定主键和版本号
update tableA set owner = ? where id =? and version = ?指定主键及与更新字段相关的条件
update tableA set owner = ? where id = ? and owner =?更新值与原值相关
update tableA set totalNum = totalNum + ? where id = ?相当于如下：
1) open a transaction
2) fetch the data (SELECT totalNum FROM tableA WHERE id = ?;)
3) do your work (totalNum + amount)
4) update the data (UPDATE tableA SET totalNum = ? WHERE id = 1;)
5) commit