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mysql中完整的select语句的用法

这篇文章主要讲解了MySQL中完整的select语句的用法,内容清晰明了,对此有兴趣的小伙伴可以学习一下,相信大家阅读完之后会有帮助。

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完整语法:

先给一下完整的语法,后面将逐一来讲解。

基础语法:select 字段列表 from 数据源;

完整语法:select 去重选项 字段列表 [as 字段别名] from 数据源 [where子句] [group by 子句] [having子句] [order by 子句] [limit子句];


去重选项::

示例:

去重前:mysql中完整的select语句的用法 ,去重后mysql中完整的select语句的用法

create table student(name varchar(15),gender varchar(15));
insert into student(name,gender) values("lilei","male");
insert into student(name,gender) values("lilei","male");
select * from student;
select distinct * from student;

补充:


字段别名:

示例:

使用前:mysql中完整的select语句的用法,使用后mysql中完整的select语句的用法

create table student(name varchar(15),gender varchar(15));
insert into student(name,gender) values("lilei","male");
insert into student(name,gender) values("lilei","male");
select * from student;
select name as "姓名",gender as "性别" from student;

数据源:


where子句:

where几种语法:

补充:

select name as n ,gender from student where name ="lilei";
-- select name as n ,gender from student where n ="lilei"; --报错
select name as n ,gender from student having n ="lilei";

group by 子句:

-- 示例
select name,gender,count(name) as "组员" from student as d group by name;
select name,gender,count(name) as "组员" from student as d group by name,gender;

补充:


having子句:

-- 示例
select name as n ,gender from student having n ="lilei";
select name,gender,count(*) as "组员" from student as d group by name,gender having count(*) >2 ;-- 这里只显示记录数>2的分组

order by 子句:

-- 示例
select * from student order by name;
select * from student order by name,gender;
select * from student order by name asc,gender desc;

limit子句:

-- 示例
select * from student limit 1;
select * from student limit 3,1;
select * from student where name ="lilei" limit 1;
select * from student where name ="lilei" limit 3,1;

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