[MSSQL] 巧秒运用On来进行联合查询
On在查询中已经不少见了,不过用On可有秒处了
不用On与用where进行查询时
select a.ID,a.G_Title,Count(b.ID) from [TD_GuideTag] as a left outer join [TD_Engine] as b on (a.ID = b.E_TagID) where (b.E_Url like '%我们%' or b.E_Name like '%我们%' or b.E_IndexUrl like'%我们%') Group by a.ID,a.G_Title,a.G_OrderNumeric,a.G_UpDateTime order by a.G_OrderNumeric asc,a.G_UpDateTime desc
发现当a表中有数据,于b表中没有数据时,查询的结果为空不用On与用where进行查询时
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
很多时候我们想就算没有数据也要显示时,用这个最好不过了。
决不做一个程序代码的写手.