MySQL高级语句(一)
2024-10-12 19:27:53
一、MySQL高级进阶SQL 语句
1、SELECT
2、DISTINCT
3、WHERE
5、IN
6、BETWEEN
7、通配符、LIKE
8、ORDER BY
9、| | 连接符
二、函数
1、数学函数
3、字符串函数
准备工作
1、安装MySQL数据库
2、实验准备,数据表配置
1 mysql -uroot -p
2 show databases;
3
4 create database train_ticket;
5 use train_ticket;
6 create table REGION(region varchar(10),site varchar(20));
7 create table FARE(site varchar(20),money int(10),date varchar(15));
8
9 desc REGION;
10 desc FARE;
11
12 insert into REGION values ('south','changsha');
13 insert into REGION values ('south','nanchang');
14 insert into REGION values ('north','beijing');
15 insert into REGION values ('north','tianjin');
16
17 insert into FARE values ('changsha',1000,'2021-01-30');
18 insert into FARE values ('nanchang',700,'2021-01-30');
19 insert into FARE values ('beijing',1500,'2021-01-30');
20 insert into FARE values ('tianjin',1200,'2021-01-30');
21 insert into FARE values ('beijing',2200,'2021-02-05');
22
23 select * from REGION;
24 select * from FARE;
一、MySQL高级进阶SQL 语句
1、SELECT
显示表格中一个或数个字段的所有资料
语法:SELECT 字段 FROM 表名
select distinct region from REGION;
2、DISTINCT
不显示重复的资料(去重)
语法:SELECT DISTINCT 字段 FROM 表名
select distinct region from REGION;
3、WHERE
有条件查询
语法:SELECT 字段 FROM 表名 WHERE 条件
select site from FARE where money > 1000;
select site from FARE where money < 1000;
select site from FARE where money = 1000;
4、AND、OR
and(并且)、or(或者)
语法:SELECT 字段 FROM 表名 WHERE 条件1 ([AND|OR] 条件2)+;
select site from FARE where money > 1000 and (money < 1500); select site,money from FARE where money < 500 or (money < 1500 and money >= 700); select site,money,date from FARE where money >= 500 and (date < '2021-02-05' and money < 1000);
5、IN
显示已知的值的资料
语法:SELECT 字段 FROM 表名 WHERE 字段 IN (‘值1’,‘值2’,……);
select site,money from FARE where money in (700,1000);
6、BETWEEN
显示两个值范围内的资料
语法:SELECT 字段 FROM 表名 WHERE 字段 BETWEEN ‘值一’ and ‘值二’;
select * from FARE where money between 500 and 1000;
7、通配符、LIKE
通常通配符都是跟LIKE一起使用
LIKE:用于匹配模式来查找资料
语法:SELECT 字段 FROM 表名 WHERE 字段 LIKE ‘模式’;
select * from FARE where site like 'be%';
select site,money from FARE where site like '%jin_';
8、ORDER BY
按关键字排序
语法:SELECT 字段 FROM 表名 [WHERE 条件] ORDER BY 字段 [ASC,DESC];
select * from FARE order by money desc;
select date,money from FARE order by money desc;
9、| | 连接符
- 如果sql_mode开启开启了PIPES_AS_CONCAT,"||"视为字符串的连接操作符而非或运算符,和字符串的拼接函数Concat相类似,这和Oracle数据库使用方法一样的
mysql -uroot -p
use train_ticket; select region || ' ' || site from REGION where region = 'north';
select site || ' ' || money || ' ' || date from FARE;
10、GROUP BY
- BY后面的栏位的查询结果进行汇总分组,通常是结合聚合函数一起使用的
- GROUP BY 有一个原则,就是 SELECT 后面的所有列中,没有使用聚合函数的列,必须出现在GROUP BY后面。
语法:SELECT 字段1,SUM(字段2) FROM 表名 GROUP BY 字段1;
select site,sum(money) from FARE group by site;
select site,sum(money),date from FARE group by site order by money desc;
select site,count(money),sum(money),date from FARE group by site order by money desc;
11、HAVING
- 用来过滤由GROUP BY语句返回的记录集,通常与GROUP BY语句联合使用。
- HAVING语句的存在弥补了WHERE关键字不能与聚合函数联合使用的不足。如果被SELECT的只有函数栏,那就不需要GROUP BY子句。
语法:SELECT 字段1,SUM(字段2) FROM 表名 GROUP BY 字段1 HAVING(函数条件);
select site,count(money),sum(money),date from FARE group by site having sum(money) >=700;
二、函数
1、数学函数
select abs(-1),rand(),mod(5,3),power(2,3),round (1.579),round(1.734,2); select sqrt(9),truncate(1.234,2),ceil(1.2),floor(1.9),greatest(1,2,3,4),least(1,2,3,4);
2、聚合函数
select avg(money) from FARE;
select count(money) from FARE;
select min(money) from FARE;
select max(money) from FARE;
select sum(money) from FARE;
- #count(*)包括所有列的行数,在统计结果时,不好忽略值为null
- #count(字段)只包括那一行的列数,在统计结果的时候,会忽略列值为null的值
3、字符串函数
SELECT TRIM ([ [位置] [要移除的字符串] FROM ] 字符串);
- #[位置]:的值可以为 LEADING (起头), TRAILING (结尾), BOTH (起头及结尾)。
- #[要移除的字符串]:从字串的起头、结尾,或起头及结尾移除的字符串。缺省时为空格。
1 select trim(leading 'na' from 'nanchang');
2 select trim(trailing '--' from 'nanchang--');
3 select trim(both '--' from '--nanchang--');
4
5 select concat(region,site) from REGION where region = 'south';
6 select concat(region,' ',site) from REGION where region = 'south';
7
8 select substr(money,1,2) from FARE;
9
10 select length(site) from FARE;
11
12 select replace(site,'ji','--') from FARE;
13
14 select upper(site) from FARE;
15
16 select lower('HAHAHA');
17
18 select left(site,2) from FARE;
19
20 select right(site,3) from FARE;
21
22 select repeat(site,2) from FARE;
23
24 select space(2);
25
26 select strcmp(100,200);
27
28 select reverse(site) from FARE;
最新文章
- 在阿里云服务器(ECS)上从零开始搭建nginx服务器
- ORA-27101 ORACLE not available
- jQuery EasyUI教程之datagrid应用(二)
- 手动配置 Android SDK
- osharp3使用经验:整合DbContextScope 文章 1
- mysql 查看正在运行的进程
- Java——FIle:
- JAVA的UML
- iOS类别(category)不能添加成员变量但是可以添加属性的问题
- BZOJ1669: [Usaco2006 Oct]Hungry Cows饥饿的奶牛
- Mac下Sublime快捷键
- GNU GPL介绍
- 小心LinkedHashMap的get()方法(转)
- 做多了国际化项目,你怎么处理时区不同的各种blabla...问题
- POJ 2154 Color [Polya 数论]
- ABP学习之路--切换mysql数据库
- MySQL This function has none of DETERMINISTIC, NO SQL...错误1418 的原因分析及解决方法 (转)
- 编译u-boot问题总结
- WKWebView中HTML5获取位置失败
- 用 Python 带你看《我不是药神》