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子查询匹配两个值

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	`1`	`+**************************************************************************************************`
	`2`	`+将子查询改为join写法时要注意表中关系是不是一对多或多对多,这种情况下要对查询结果使用distinct去重。`
	`3`	`+`
	`4`	`+**************************************************************************************************`
	`5`	`+select a.user_name,b.timestr,kills from user1 a join user_kills b on`
	`6`	`+ a.id=b.user_id join(select user_id,max(kills) as cnt from user_kills group by user_id)c on`
	`7`	`+ b.user_id=c.user_id and b.kills=c.cnt;`
	`8`	`+`
	`9`	`+mysql中独有的列过滤方式:多列过滤`
	`10`	`+select a.user_name,b.timestr,kills`
	`11`	`+from user1 a`
	`12`	`+join user_kills b on a.id=b.user_id`
	`13`	`+where (b.user_id,b.kills) in (`
	`14`	`+ select user_id,max(kills)`
	`15`	`+ from user_kills`
	`16`	`+ group by user_id`
	`17`	`+);`
	`18`	`+`

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