MySQL学习必备SQL_DDL_DQL

1.学生表

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 NULL,
  `introduce` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8;

2.插入学生信息

insert into student values(0,'2024-02-25 10:10:10','赵灵儿','123',
'15612345678',16,'女','逍遥哥哥，你终于找到我了。');
insert into student values(0,'2024-02-25 10:10:10','王语嫣','123',
'15612345678',17,'女','慕容复，我和你不共戴天。');
insert into student values(0,'2024-02-25 10:10:10','龙姑娘','123',
'15612345678',22,'女','我想过过过儿时过过的日子。');
insert into student values(0,'2024-02-25 10:10:10','杨过','123',
'15612345678',18,'男','一遇杨过误终身。');
insert into student values(0,'2024-02-25 10:10:10','杨逍','123',
'15612345678',27,'男','杨过跟程英的大儿子。');
insert into student (userName,age,introduce)values('黄衣女子',26,'杨过与龙姑娘的大女儿。');

实际情况

3.基础查询设置DQL

#基础查询
select * from student;
#筛选列表（匿名）与筛选数据行
select userName as 姓名,age'年龄',sex'性别',introduce'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）开始查询查2条。
#排序，order by根据数值类型进行排序会比较准确。
select * from student order by age desc limit 3;
#去重语句distinct
select distinct sex '性别类型' from student;