查询的基本语法

select * from 表名;

1. from关键字后面写表名，表示数据来源于是这张表
2. select后面写表中的列名，如果是*表示在结果中显示表中所有列
3. 在select后面的列名部分，可以使用as为列起别名，这个别名出现在结果集中
4. 如果要查询多个列，之间使用逗号分隔

在select后面列前使用distinct可以消除重复的行

select distinct gender from students;

select * from 表名 where 条件;

select * from students where id>3;

select * from subjects where id<=4;

select * from students where sname!=‘黄蓉‘;

select * from students where isdelete=0;

select * from students where id>3 and gender=0;

select * from students where id<4 or isdelete=0;

select * from students where sname like ‘黄%‘;

select * from students where sname like ‘黄_‘;

select * from students where sname like ‘黄%‘ or sname like ‘%靖%‘;

select * from students where id in(1,3,8);

select * from students where id between 3 and 8;

select * from students where id between 3 and 8 and gender=1;

select * from students where hometown is null;

select * from students where hometown is not null;

select * from students where hometown is not null and gender=0;