My QPL学习

1、学生表DDL

CREATE TABLE `student` (
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '学号',
  `createDate` datetime DEFAULT NULL,
  `userName` varchar(20) DEFAULT NULL,
  `pwd` varchar(36) DEFAULT NULL,
  `phone` varchar(11) DEFAULT NULL,
  `age` tinyint(3) DEFAULT NULL,
  `sex` char(2) DEFAULT '男',
  `introduce` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=24 DEFAULT CHARSET=utf8;

2、插入学生信息DML

insert into student values(0,'2024-02-25 10:00:00','赵灵儿','123',
'15612345678',16,'女','逍遥哥，你找到我。');
insert into student values(0,'2024-02-25 10:00:00','王语嫣','123',
'15612345678',17,'女','不共戴天。');
insert into student values(0,'2024-02-25 10:00:00','龙姑娘','123',
'15612345678',22,'女','过儿过上好日子。');
insert into student values(0,'2024-02-25 10:00:00','杨过','123',
'15612345678',18,'男','误终身。');
insert into student values(0,'2024-02-25 10:00:00','杨晓','123',
'15612345678',27,'男','杨过大儿子。');
insert into student (userName,age,introduce)values('黄衣女子',26,
'杨过大女儿。');

3、基础查询测试

select * from student;
select userName as 姓名，age'年龄',sex'性别',intriduce'简介'
from student
where pwd is not null;
#分页 limit.有两个重载函数常用，
#1 一个参数为显示条数
#2 一个参数为从那条开始查询（下标从0开始计算），零-参数为显示条数
select * from student limit 3,2;# 从4（0-3）开始查询两条。
#排序，order by 根据数据类型进行排序比较准确。
select * from student order by age dess limit 3;
#去重语句distinct
select distinct sex '性别类型' from student;