select messages.*,virtualUser.loginname,virtualUser.companyname from(select smsgroupid,userid,count(*) as groupnums,SUM(successnum) as sumsuccessmsg,msg,senddate,SUM(failurenum) as sumfailmsg,state from messages where exists(select 3927 as id) and senddate between '2009-01-20 00:00:00' and '2009-02-19 06:10:21' group by smsgroupid,userid limit 20) messages left join users virtualUser on messages.userid = virtualUser.id
这条语句看不明白,from(select smsgroupid,userid,count(*) as groupnums,SUM(successnum) as sumsuccessmsg,msg,senddate,SUM(failurenum) as sumfailmsg,state from messages where exists(select 3927 as id) and senddate between '2009-01-20 00:00:00' and '2009-02-19 06:10:21' group by smsgroupid,userid limit 20)
这段是什么意思呢?
这条语句看不明白,from(select smsgroupid,userid,count(*) as groupnums,SUM(successnum) as sumsuccessmsg,msg,senddate,SUM(failurenum) as sumfailmsg,state from messages where exists(select 3927 as id) and senddate between '2009-01-20 00:00:00' and '2009-02-19 06:10:21' group by smsgroupid,userid limit 20)
这段是什么意思呢?
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这一段怎么理解?
不等。select 3927 as id ;是直接取一个 数字 3927 做为伪列 idselect id from table where id = 3927
是从表table中取一个id=3927记录的id字段的值。
建议看一下数据库原理。否则很难再往细里讲清楚了。