MySQL学习必备SQL_DDL_DML_DQL

mysql创建

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=1 DEFAULT CHARSET=utf8;

2、插入学生信息

INSERT INTO student VALUES(0,'2024-02-25 10:00:00','海绵宝宝','123','1512345678',16,'男','比奇堡')
INSERT INTO student VALUES(0,'2024-02-25 10:00:00','派大星','123','1512345678',16,'男','贝壳')
INSERT INTO student VALUES(0,'2024-02-25 10:00:00','珊迪','123','1512345678',16,'女','松鼠')
INSERT INTO student VALUES(0,'2024-02-25 10:00:00','章鱼哥','123','1512345678',16,'男','章鱼')
INSERT INTO student VALUES(0,'2024-02-25 10:00:00','痞老板','123','1512345678',16,'男','微生物')
INSERT INTO student (username,age,introduce)VALUES('蟹老板','26','钱')

显示效果

3、基础查询测试

#基础查询
SELECT * FROM student;
#筛选列与筛选数据行
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
#一个参数为显示条数
#一个参数为从那条开始查询（下表从0开始计算），零一参数为显示条数
select * FROM student LIMIT 3,2;
#从4开始查询2条
SELECT * FROM student orser by age DESC limit 3;#排序，order by根据数值类型进行排序会比较准确
SELECT DISTINCT sex '性别类型' FROM student;#去重语句distinct