mysql -uroot -p
show databases;
create database train_ticket;
use train_ticket;
create table REGION(region varchar(10),site varchar(20));
create table FARE(site varchar(20),money int(10),date varchar(15));
desc REGION;
desc FARE;
insert into REGION values ('south','changsha');
insert into REGION values ('south','nanchang');
insert into REGION values ('north','beijing');
insert into REGION values ('north','tianjin');
insert into FARE values ('changsha',1000,'2021-01-30');
insert into FARE values ('nanchang',700,'2021-01-30');
insert into FARE values ('beijing',1500,'2021-01-30');
insert into FARE values ('tianjin',1200,'2021-01-30');
insert into FARE values ('beijing',2200,'2021-02-05');
select * from REGION;
select * from FARE;
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二、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 region from REGION;
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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;
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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;
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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);
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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);
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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;
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7、通配符、LIKE
通常通配符都是跟LIKE一起使用
%:百分号表示零个、一个或多个字符
_:下划线表示单个字符
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_';
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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];
#ASC:按照升序进行排序,默认的排序方式
#DESC:按照降序进行排序
select * from FARE order by money desc;
select date,money from FARE order by money desc;
#[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。
select trim(leading 'na' from 'nanchang');
select trim(trailing '--' from 'nanchang--');
select trim(both '--' from '--nanchang--');
select concat(region,site) from REGION where region = 'south';
select concat(region,' ',site) from REGION where region = 'south';
select substr(money,1,2) from FARE;
select length(site) from FARE;
select replace(site,'ji','--') from FARE;
select upper(site) from FARE;
select lower('HAHAHA');
select left(site,2) from FARE;
select right(site,3) from FARE;
select repeat(site,2) from FARE;
select space(2);
select strcmp(100,200);
select reverse(site) from FARE;
mysql -uroot -p
use train_ticket;
select region || ' ' || site from REGION where region = 'north';
select site || ' ' || money || ' ' || date from FARE;
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5、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;
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;
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7、别名
字段别名、表格别名
语法:SELECT “表格別名”.“字段1” [AS] “字段1別名” FROM “表格名” [AS] “表格別名”;
select RE.region AS reg, count(site) from REGION AS RE group by reg;
select FA.site AS si,sum(money),count(money),date AS da from FARE AS FA group by si;
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8、子查询
连接表格,在WHERE 子句或HAVING 子句中插入另一个SQL 语句
语法:SELECT 字段1 FROM 表格1 WHERE 字段2 [比较运算符] (SELECT 字段1 FROM 表格2 WHERE 条件)
可以是符号的运算符
例:=、>、<、>=、<=
也可以是文字的运算符
例:LIKE、IN、BETWEEN
select A.site,region from REGION AS A where A.site in(select B.site from FARE AS B where money<2000);
select B.site,money,date from FARE AS B where site in(select A.site from REGION AS A where region = 'north');