编辑代码

-- DQL 执行顺序与编写顺序区分开
-- DQL的编写顺序,select 字段列表 from 表名 where 条件列表 group by 字段分组列表 having 分组后条件列表
-- order by 排序字段列表 limit 分页参数;
-- DQL的执行顺序 ① from → ② where → ③ group by → ④ select → ⑤ order by → ⑥ limit
create database info;
use info;
create table worker(
    id int,
    name varchar(10),
    age int,
    gender char(1),
    workcity varchar(10),
    entrytime date
);
insert into worker values (1,'张三',28,'F','上海','2020-08-20');
insert into worker values(2,'李四',24,'F','上海','2021-06-25');
insert into worker values(3,'王二麻',27,'M','北京','2020-07-22');
insert into worker values(4,'王五',29,'M','深圳','2022-01-10');
insert into worker values(5,'赵六',32,'F','深圳','2019-07-07');
insert into worker values(6,'钱九',31,'M','北京','2018-04-19');
insert into worker values(7,'孙八',30,'F','深圳','2021-09-17');
insert into worker values(8,'何十',34,'M','北京','2022-03-28');
insert into worker values(9,'九九',26,'M','深圳','2023-08-19');
insert into worker values(10,'零七',24,'F','上海','2021-06-24');
insert into worker values(11,'可可',27,'M',null,'2024-07-21');

-- select * from worker;
-- DQL的执行顺序 ① from → ② where → ③ group by → ④ select → ⑤ order by → ⑥ limit
select w.name,w.id from worker w where w.age < 30 order by w.age DESC;