比较两sql文的查询结果有什么区别 马下结贴
日期：2014-05-17 浏览次数：20353 次
比较两sql文的查询结果有什么区别 马上结贴
select top 100 teststudent.testarrangeid,teststudent.studentuserid,teststudent.paperid,answersheet.studentid,answersheet.score,answersheet.studentname,answersheet.paperid,u.usercode,u.chinesename as truename,paper.paperdesignid from teststudent
inner join userinfo u on teststudent.studentuserid=u.userid
left join answersheet on u.name=answersheet.studentid and answersheet.paperid=teststudent.paperid
inner join paper on paper.paperid=teststudent.paperid
where teststudent.paperid=32
----------------------------------------
select top 100 teststudent.studentuserid from teststudent
inner join userinfo u on teststudent.studentuserid=u.userid
left join answersheet on u.name=answersheet.studentid and answersheet.paperid=teststudent.paperid
inner join paper on paper.paperid=teststudent.paperid
where teststudent.paperid=32
第一个查询结果：
第二个查询结果：
studentuserid
-------------
1036
1075
2484
2558
2583
2611
只要注意 studentuserid 字段， 看区别， 为什么会这样？
------解决方案--------------------
Order by 唯一属性
------解决方案--------------------
select top 100 teststudent.testarrangeid,teststudent.studentuserid,teststudent.paperid,answersheet.studentid,answersheet.score,answersheet.studentname,answersheet.paperid,u.usercode,u.chinesename as truename,paper.paperdesignid from teststudent
inner join userinfo u on teststudent.studentuserid=u.userid
left join answersheet on u.name=answersheet.studentid and answersheet.paperid=teststudent.paperid
inner join paper on paper.paperid=teststudent.paperid
where teststudent.paperid=32
----------------------------------------
select top 100 teststudent.studentuserid from teststudent
inner join userinfo u on teststudent.studentuserid=u.userid
left join answersheet on u.name=answersheet.studentid and answersheet.paperid=teststudent.paperid
inner join paper on paper.paperid=teststudent.paperid
where teststudent.paperid=32
第一个查询结果：
- SQL code
testarrangeid studentuserid paperid studentid score studentname paperid usercode truename paperdesignid ------------- ------------- ----------- -------------------- ----------------------------------------------------- ------------------------------ ----------- ---------------------------------------------------------------- -------------------------------------------------- ------------- 28 1036 32 S1132012147 54.0 NULL 32 1132012147 戴翠叶 33 28 1075 32 S1132012227 73.0 NULL 32 1132012227 廖荣华 33 28 9198 32 S1101092133 76.0 NULL 32 1101092133 柴琳 33 28 9199 32 S1101092134 74.0 NULL 32 1101092134 王艺 33 28 9200 32 S1101092135 62.0 NULL 32 1101092135 孙萌 33 28 9201 32 S1101092136 81.0 NULL 32 1101092136 王晶 33
第二个查询结果：
studentuserid
-------------
1036
1075
2484
2558
2583
2611
只要注意 studentuserid 字段， 看区别， 为什么会这样？
------解决方案--------------------
Order by 唯一属性
------解决方案--------------------
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