mysql-单表操作

mySql单表操作主要有一下内容：

1.查询：查询又分为几种，范围查询，模糊查询、空值查询、多条件查询

查询的语句格式为：SELECT 字段 1，字段 2，字段 3...FROM 表名 WHERE 条件表达式

1.1-in：范围查询：SELECT 字段 1，字段 2，字段 3...FROM 表名 WHERE 字段 [NOT] IN (元素 1，元素 2，元素 3)

1.1-BETWEEN AND：范围查询：SELECT 字段 1，字段 2，字段 3...FROM 表名 WHERE 字段 [NOT] BETWEEN 取值 1 AND 取值 2
 1.2：模糊查询：SELECT 字段 1，字段 2，字段 3...FROM 表名 WHERE 字段 [NOT] LIKE ‘字符串’
    1.2.1：%匹配多个字符

1.2.2:_匹配单个字符

1.3.空值查询：SELECT 字段 1，字段 2，字段 3...FROM 表名 WHERE 字段 IS [NOT] NULL

1.4.多条件查询-and：SELECT 字段 1，字段 2...FROM 表名 WHERE 条件表达式 1 AND 条件表达式 2 [...AND 条件表达式 n]

1.5.多条件查询-or：SELECT 字段 1，字段 2...FROM 表名 WHERE 条件表达式 1 OR 条件表达式 2 [...OR 条件表达式 n]

2.去重：SELECT DISTINCT 字段名 FROM 表名；

3.排序：SELECT 字段 1，字段 2...FROM 表名 ORDER BY 属性名 [ASC|DESC]

4.分组：GROUP BY 属性名 [HAVING 条件表达式][WITH ROLLUP]

4.1 分组元素统计：SELECT gradeName,GROUP_CONCAT(stuName) FROM t_student GROUP BY gradeName;--把每个年级的学生名字全部放在一个字符串里面，以逗号隔开

4.2 分组数量统计：SELECT gradeName,COUNT(stuName) FROM t_student GROUP BY gradeName;

4.3 对分组进行过滤：SELECT gradeName,COUNT(stuName) FROM t_student GROUP BY gradeName HAVING COUNT(stuName)>3;

5.分页：SELECT 字段 1，字段 2...FROM 表名 LIMIT 初始位置，记录数；

以上就是单表基本操作-------------------------------------------------------------------------------------------------------

/*
SQLyog 企业版 - MySQL GUI v8.14
MySQL - 5.1.49-community
*********************************************************************
*/
/*!创建学生表*/;

create table `t_student` (
`id` double ,
`stuName` varchar (60),
`age` double ,
`sex` varchar (30),
`gradeName` varchar (60)
);

//插入数据
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('1','张三','23','男','一年级');
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('2','张三丰','25','男','二年级');
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('3','李四','23','男','一年级');
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('4','王五','22','男','三年级');
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('5','珍妮','21','女','一年级');
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('6','李娜','26','女','二年级');
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('7','王峰','20','男','三年级');
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('8','梦娜','21','女','二年级');
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('9','小黑','22','男','一年级');
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('10','追风','25','男','二年级');
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('11','小小张三','21',NULL,'二年级');
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('12','小张三','23','男','二年级');
insert into `t_student` (`id`, `stuName`, `age`, `sex`, `gradeName`) values('13','张三锋小','24',NULL,'二年级');

//单表操作

SELECT id,stuName,age,sex,gradeName FROM t_student ;

SELECT stuName,id,age,sex,gradeName FROM t_student ;

SELECT * FROM t_student;

SELECT stuName,gradeName FROM t_student;

SELECT * FROM t_student WHERE id=1;

SELECT * FROM t_student WHERE age>22;

SELECT * FROM t_student WHERE age IN (21,23);
SELECT * FROM t_student WHERE age NOT IN (21,23);

SELECT * FROM t_student WHERE age BETWEEN 21 AND 24;
SELECT * FROM t_student WHERE age NOT BETWEEN 21 AND 24;

SELECT * FROM t_student WHERE stuName LIKE '张三';
SELECT * FROM t_student WHERE stuName LIKE '张三%';
SELECT * FROM t_student WHERE stuName LIKE '张三__';
SELECT * FROM t_student WHERE stuName LIKE '%张三%';

SELECT * FROM t_student WHERE sex IS NULL;
SELECT * FROM t_student WHERE sex IS NOT NULL;

SELECT * FROM t_student WHERE gradeName='一年级' AND age=23
SELECT * FROM t_student WHERE gradeName='一年级' OR age=23

SELECT DISTINCT gradeName FROM t_student;

SELECT * FROM t_student ORDER BY age ASC;
SELECT * FROM t_student ORDER BY age DESC;

SELECT * FROM t_student GROUP BY gradeName;

SELECT gradeName,GROUP_CONCAT(stuName) FROM t_student GROUP BY gradeName;

SELECT gradeName,COUNT(stuName) FROM t_student GROUP BY gradeName;

SELECT gradeName,COUNT(stuName) FROM t_student GROUP BY gradeName HAVING COUNT(stuName)>3;

SELECT gradeName,COUNT(stuName) FROM t_student GROUP BY gradeName WITH ROLLUP;
SELECT gradeName,GROUP_CONCAT(stuName) FROM t_student GROUP BY gradeName WITH ROLLUP;

SELECT * FROM t_student LIMIT 0,5;
SELECT * FROM t_student LIMIT 5,5;
SELECT * FROM t_student LIMIT 10,5;

；