Python学习第二十三课——Mysql 表记录的一些基本操作（查）

查(select * from 表名)

　　select <字段1，字段2，...> from <表名> where <表达式>;

　　例如，查询student表中所有的记录，在终端窗口输入命令：

　　select id,name,age from employee;

也可以查询限定的记录，输入如下命令，可以限定查询结果为第0条到第1条记录，也就是返回第一条记录：

select * from empolyee limit 0,3;

select * from employee where age between 18 and 20;

select * from employee where name like "阿%";

select name from employee where salary is null;

select name,chengji from employee order by chengji;

select name,chengji from employee where chengji>50 order by chengji;

select name,chengji from employee where chengji>50 order by chengji desc;

select name,chengji1+chengji2 as 总成绩 from employee;

select name,chengji1+chengji2 as 总成绩 from employee order by 总成绩;

注意：按分组条件分组每一组只会显示第一条记录；


  select * from employee group by name;(按照name分组  name一样的将被分为一组)