two,mySQL多表查询

一,DQL语句 ;将数据库所有数据查询出来,select字段,from表名,where条件.不够 1).比较运算符; > 大于 < 小于 <=小于等于 >=大于等于 <>,!=不等于Select * from student where english>80. 2).逻辑运算符; and , or ,notSelect * from student where math> 20 and sex =

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