left join 与where 两种关联区别例如:select * from a left join b on a.no=b.no与语句 select * from a,b where a.no=b.no的区别,那个性能更优
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![left join 与where 两种关联区别例如:select * from a left join b on a.no=b.no与语句 select * from a,b where a.no=b.no的区别,那个性能更优](/uploads/image/z/14527957-13-7.jpg?t=left+join+%E4%B8%8Ewhere+%E4%B8%A4%E7%A7%8D%E5%85%B3%E8%81%94%E5%8C%BA%E5%88%AB%E4%BE%8B%E5%A6%82%EF%BC%9Aselect+%2A+from+a+left+join+b+on+a.no%3Db.no%E4%B8%8E%E8%AF%AD%E5%8F%A5+select+%2A+from+a%2Cb+where+a.no%3Db.no%E7%9A%84%E5%8C%BA%E5%88%AB%2C%E9%82%A3%E4%B8%AA%E6%80%A7%E8%83%BD%E6%9B%B4%E4%BC%98)
left join 与where 两种关联区别例如:select * from a left join b on a.no=b.no与语句 select * from a,b where a.no=b.no的区别,那个性能更优
left join 与where 两种关联区别
例如:select * from a left join b on a.no=b.no
与语句 select * from a,b where a.no=b.no
的区别,那个性能更优
left join 与where 两种关联区别例如:select * from a left join b on a.no=b.no与语句 select * from a,b where a.no=b.no的区别,那个性能更优
这两个的查询结果都不一样,现在很少用第二种写法,一般都是join、left join.
性能上没感觉有什么差异
left join 与where 两种关联区别例如:select * from a left join b on a.no=b.no与语句 select * from a,b where a.no=b.no的区别,那个性能更优
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