Question

sql join 和不用join 哪个效率高？

语句1：
select * from table1, table2 where table1.id=table2.id and table1.name <>'aaa' and table2.value > 50000 ;
语句2：
select * from table1 join table2 on table1.id=table2.id where table1.name <>'aaa' and table2.value > 50000;

Answer 1

结果没有区别
set statistics io on
set statistics time on
select * from table1, table2 where table1.id=table2.id and table1.name <>'aaa' and table2.value > 50000
set statistics io off
set statistics time off

set statistics io on
set statistics time on
select * from table1 join table2 on table1.id=table2.id where table1.name <>'aaa' and table2.value > 50000
set statistics io off
set statistics time off
执行一下看看结果就知道了！~
看看IO扫描和CPU时间就知道了！~
相对来说第二个效率高一些

Answer 2

语句1效率高

Answer 3

语句2有错误吧。。

追问

哦 我随意写了下。。

Answer 4

这个没什么区别吧？ 一个是链接，一个不是而已