MySQL各类查询语句DQL——like_between and_null_in

创建数据库

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) unsigned DEFAULT NULL,
  `sex` char(2) DEFAULT '男',
  `introduce` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

插入数据

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。');

查询语句

#模糊查询like 基本上所有后台管理系统都会有此功能。
#like用法：where + 查询列 + like + 匹配字符串。
SELECT * FROM student WHERE userName LIKE '杨_';
SELECT * FROM student WHERE userName LIKE '杨%';
SELECT * FROM student WHERE introduce LIKE '%大%';
#null
SELECT * FROM student WHERE pwd IS NOT NULL;
#范围查询： between and 包含==，既可以查询数值范围，也可以查询时间范围，用途广泛。
SELECT * FROM student WHERE age BETWEEN 22 AND 30;
SELECT * FROM student WHERE createDate BETWEEN '2024-02-21 00:00:00' AND '2024-02-25 00:00:00';
#in的使用，不建议用此关键字，因为它不一定走索引，在百万表的数据中会很卡。
SELECT * FROM student WHERE userName IN ('赵灵儿','杨过','龙姑娘');