11-基础SQL-DQL(数据查询语言)-排序查询（ORDER BY）

DQL-介绍（常用）

DQL英文全称是Data Query Language（数据查询语言），数据查询语言用来查询数据库中表的记录

查询关键字：SELECT

DQL-语法

DQL-排序查询

语法:

SELECT 字段列表 FROM 表名 ORDER BY 字段1 排序方式, 字段2 排序方式2;

排序方式：

 

案例：创建一个 emp 员工表，添加一些员工数据

CREATE TABLE emp(
    id int comment "编号",
    workno varchar(10) comment "工号",
    name varchar(10) comment "姓名",
    gender char(1) comment "性别",
    age tinyint unsigned comment "年龄",
    idcard char(18) comment "身份证号",
    workaddress varchar(50) comment "工作地址",
    entrydate date comment "入职时间"
) comment "员工表";

INSERT INTO emp (id,workno,name,gender,age,idcard,workaddress,entrydate)
VALUES    
(1,"1","马铃薯","男","23","123456789000000000","江西","2023-8-31"),
(2,"2","任先生","男","26","123456789000000001","河北","2023-12-31"),
(3,"3","张三","女","23","123456789000000002","河北","2023-5-31"),
(4,"4","李四","女","24","123456789000000003","山西","2023-3-31")

1）根据年龄对公司的员工进行升序排序

SELECT * FROM emp ORDER BY age ASC;

2）根据入职时间，对员工及进行降序排序

SELECT * FROM emp ORDER BY entrydate DESC;

3）根据年龄对公司的员工进行升序排序，年龄相同，再按照入职时间进行降序排序

SELECT * FROM emp ORDER BY age ASC, entrydate DESC;