Mysql中on,in,as,where的区别

答：Where查询条件，on内外连接时候用,as作为别名,in查询某值是否在某条件里

创建2个表：student，score

student：

 score：

where

SELECT * FROM student WHERE s_sex='男'

例如：on

SELECT * FROM student LEFT JOIN score on student.s_id=score.s_id;

on和where组合：

SELECT * FROM student LEFT JOIN score on student.s_id=score.s_id WHERE s_name='赵雷' 

 

例如：in

SELECT * FROM score WHERE s_id in (SELECT s_id FROM student WHERE s_name='赵雷')

 

as

select * from score as a LEFT JOIN student as b on a.s_id=b.s_id where s_name='赵雷'