MySQL高级SQL语句

目录

1.MySQL进阶查询

[1.1 select](#1.1 select)

[1.2 distinct](#1.2 distinct)

[1.3 where](#1.3 where)

[1.4 and or](#1.4 and or)

[1.5 in](#1.5 in)

[1.6 between](#1.6 between)

[1.7 通配符](#1.7 通配符)

[1.8 like](#1.8 like)

[1.9 ORDER BY](#1.9 ORDER BY)

2.MySQL数据库函数

[2.1 数学函数](#2.1 数学函数)

[2.2 聚合函数](#2.2 聚合函数)

[2.3 字符串函数](#2.3 字符串函数)

[2.3.1 upper、lower大小写转换](#2.3.1 upper、lower大小写转换)

[2.3.2 concat拼接](#2.3.2 concat拼接)

[2.3.3 substr字符串截取](#2.3.3 substr字符串截取)

[2.3.3 length长度查看](#2.3.3 length长度查看)

[​2.3.3 replace替换](#2.3.3 replace替换)

[2.3.3 trim移除](#2.3.3 trim移除)

3.查询函数

[3.1 group by汇总](#3.1 group by汇总)

[3.2 having](#3.2 having)

[3.3 别名](#3.3 别名)

[3.4 子查询](#3.4 子查询)

[3.5 exists（类查询）](#3.5 exists（类查询）)

4.连接查询

[4.1 表连接](#4.1 表连接)

[4.2 内连接](#4.2 内连接)

[4.3 左连接](#4.3 左连接)

[4.3 右连接](#4.3 右连接)

5.求交集、无交集方法总结

[5.1 交集方法](#5.1 交集方法)

[5.2 求无交集方法总结](#5.2 求无交集方法总结)

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1.MySQL进阶查询

数据库实例准备：

create database tan;
use tan;
###在数据库tan中创建数据表location,并添加数据记录
create table location (Region char(20),Store_Name char(20));
insert into location values('East','Boston');
insert into location values('East','New York');
insert into location values('West','Los Angeles');
insert into location values('West','Houston');

###在数据库tan中创建数据表store_info,并添加数据记录
create table store_info (Store_Name char(20),Sales int(10),Date char(10));
insert into store_info values('Los Angeles','1500','2020-12-05');
insert into store_info values('Houston','250','2020-12-07');
insert into store_info values('Los Angeles','300','2020-12-08');
insert into store_info values('Boston','700','2020-12-08');
insert into store_info values('Washington','1000','2020-12-09');
insert into store_info values('Chicago','800','2020-12-10');

1.1 select

select:显示表格中一个或数个字段的所有数据记录

语法：SELECT "字段" FROM "表名";
select store_name from store_info;

1.2 distinct

distinct:不显示重复的数据记录

语法：SELECT DISTINCT "字段" FROM "表名";
select distinct Store_Name from store_info;

1.3 where

where:有条件查询

语法：SELECT "字段" FROM "表名" WHERE "条件";
select * from store_info where Store_Name = 'Los Angeles';
select * from store_info where Store_Name != 'Los Angeles';

1.4 and or

and or:且 或

语法：SELECT "字段" FROM "表名" WHERE "条件1" {[AND|OR] "条件2"}+ ;
select * from store_info where Sales >= 700 and Sales <= 900;
select * from store_info where Store_Name='Los Angeles' or  Store_Name = 'Houston';
mysql> select * from store_info where (Store_Name='Los Angeles' or  Store_Name = 'Houston') and sales > 1000;

1.5 in

in:显示已知的值的数据记录

语法：SELECT "字段" FROM "表名" WHERE "字段" IN ('值1', '值2', ...);
select * from store_info where Sales in (1500, 250);
等于
select * from store_info where sales=1500 or sales=250;

select * from store_info where Sales not in (1500, 250);
等于
select * from store_info where sales!=1500 and sales!=250;

1.6 between

between:显示两个值范围内的数据记录

语法：SELECT "字段" FROM "表名" WHERE "字段" BETWEEN '值1' AND '值2';
select * from store_info where date between '2020-12-05' and '2020-12-08';
等于
select * from store_info where date >='2020-12-05' and date<='2020-12-08';

1.7 通配符

通配符:通常通配符都是跟like一起使用的

% ：百分号表示零个、一个或多个字符
_ ：下划线表示单个字符

'A_Z'：所有以 'A' 起头，另一个任何值的字符，且以'Z'为结尾的字符串。例如，'ABZ' 和 'A2Z' 都符合这一个模式，而 'AKKZ' 并不符合 (因为在A和Z之间有两个字符，而不是一个字符)。
'ABC%': 所有以 'ABC' 起头的字符串。例如，'ABCD' 和 'ABCABC' 都符合这个模式。
'%XYZ': 所有以 'XYZ' 结尾的字符串。例如，'WXYZ' 和 'ZZXYZ' 都符合这个模式。
'%AN%': 所有含有 'AN'这个模式的字符串。例如，'LOS ANGELES' 和 'SAN FRANCISCO' 都符合这个模式。
'_AN%'：所有第二个字母为 'A' 和第三个字母为 'N' 的字符串。例如，'SAN FRANCISCO' 符合这个模式，而 'LOS ANGELES' 则不符合这个模式。

select * from store_info where Store_Name like '_os%';
select * from store_info where Store_Name like '%on';
select * from store_info where Store_Name like 'Los%';

1.8 like

like:匹配一个模式来找出我们要的数据记录

语法：SELECT "字段" FROM "表名" WHERE "字段" LIKE {模式};
select * from store_info where store_name like '%on%';

1.9 ORDER BY

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 是按照升序进行排序的，是默认的排序方式。
#DESC 是按降序方式进行排序。
select * from store_info order by sales;
select * from store_info order by sales desc;
select * from store_info where Store_Name in ('Los Angeles', 'Chicago') order by sales desc;

2.MySQL数据库函数

2.1 数学函数

|-------------------------|---------------------------|
| 数学函数 | 作用 |
| abs(x) | 返回x的绝对值 |
| rand() | 返回0到1的随机数 |
| mod(x, y) | 返回x除以y以后的余数 |
| power(x, y) | 返回x的y次方 |
| round(x) | 返回离x最近的整数 |
| round(x, y) | 保留x的y位小数四舍五入后的值 |
| sqrt(x) | 返回x的平方根 |
| truncate(x, y) | 返回数字x截断为y位小数的值 #不四舍五入 |
| ceil(x) | 返回大于或等于x的最小整数 |
| floor(x) | 返回小于或等于x的最大整数 |
| greatest(x1,x2,...) | 返回集合中最大的值 |
| least(x1,x2,...) | 返回集合中最小的值 |

SELECT abs(-1), rand(), mod(5,3), power(2,3), round(1.89);
SELECT round(1.8937,3), truncate(1.235,2), ceil(5.2), floor(2.1), least(1.89,3,6.1,2.1);

2.2 聚合函数

|-------------|-----------------------|
| 关键字 | 作用 |
| avg() | 返回指定列的平均值 |
| count() | 返回指定列中非 NULL 值的个数 |
| min() | 返回指定列的最小值 |
| max() | 返回指定列的最大值 |
| sum(字段) | 返回指定列的所有值之和 |

###返回指定列sales的平均值
select avg(sales) from store_info;

###返回指定列store_name列中非NULL值的个数
select count(store_name) from store_info;
select count(distinct store_name) from store_info;

2.3 字符串函数

|--------------------|-------------------------------------------------|
| 字符串函数 | 作用 |
| trim() | 返回去除指定格式的值 |
| concat(x,y) | 将提供的参数 x 和 y 拼接成一个字符串 |
| substr(x,y) | 获取从字符串 x 中的第 y 个位置开始的字符串，跟substring()函数作用相同 |
| substr(x,y,z) | 获取从字符串 x 中的第 y 个位置开始长度为 z 的字符串 |
| length(x) | 返回字符串 x 的长度 |
| replace(x,y,z) | 将字符串 z 替代字符串 x 中的字符串 y |
| upper(x) | 将字符串 x 的所有字母变成大写字母 |
| lower(x) | 将字符串 x 的所有字母变成小写字母 |
| left(x,y) | 返回字符串 x 的前 y 个字符 |
| right(x,y) | 返回字符串 x 的后 y 个字符 |
| repeat(x,y) | 将字符串 x 重复 y 次 |
| space(x) | 返回 x 个空格 |
| strcmp(x,y) | 比较 x 和 y，返回的值可以为-1,0,1 |
| reverse(x) | 将字符串 x 反转 |

补充：字符串截取三种方法

2.3.1 upper、lower大小写转换

2.3.2 concat拼接

使用"||"进行拼接

2.3.3 substr字符串截取

2.3.3 length长度查看

2.3.3 replace替换

2.3.3 trim移除

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。

2.3.3 left、right取值

3.查询函数

3.1 group by汇总

group by:对group by后面字段的查询结果,进行汇总分组，通常是结合聚合函数一起使用的

语法：SELECT "字段1", SUM("字段2") FROM "表名" GROUP BY "字段1";
select * from store_info group by Store_Name;
select Store_Name, count(Sales) from store_info group by Store_Name;

3.2 having

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

语法：SELECT "字段1", SUM("字段2") FROM "表格名" GROUP BY "字段1" HAVING (函数条件);
 select store_name,sum(sales) from store_info group by store_name having sum(sales) > 1000;

3.3 别名

别名:字段別名 表格別名

语法：SELECT "表格別名"."字段1" [AS] "字段別名" FROM "表格名" [AS] "表格別名";
select A.store_name store,sum(A.sales) "total sales" from store_info A group p by A.store_name;

3.4 子查询

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] 				#外查询
(SELECT "字段1" FROM "表格2" WHERE "条件");									#内查询

#可以是符号的运算符，例如 =、>、<、>=、<= ；也可以是文字的运算符，例如 LIKE、IN、BETWEEN
select sum(Sales) from store_info where Store_Name in (select Store_Name from location where Region='West');
st');

select sum(Sales) from store_info where Store_Name in (select Store_Name from location where Region='West');

3.5 exists（类查询）

exists:用来根据条件过滤查询结果，并只返回满足条件的行

语法：SELECT "字段1" FROM "表格1" WHERE EXISTS (SELECT * FROM "表格2" WHERE "条件");
#这里的子查询作为条件进行判断。如果子查询返回至少一行结果，则外部查询的结果将包含该行

select * from store_info A where exists (select Store_Name from location B where B.store_name = A.store_name);

4.连接查询

4.1 表连接

|---------------------|-------------------------------|
| 表连接方式 | 含义 |
| inner join(内连接) | 只返回两个表中联结字段相等的行 |
| left join(左连接) | 返回包括左表中的所有记录和右表中联结字段相等的记录 |
| right join(右连接) | 返回包括右表中的所有记录和左表中联结字段相等的记录 |

4.2 内连接

select * from store_info A inner join location B on A.Store_Name=B.Store_Name;

4.3 左连接

select * from store_info A left join location B on A.Store_Name=B.Store_Name;

4.3 右连接

select * from store_info A right join location B on A.Store_Name=B.Store_Name;

5.求交集、无交集方法总结

5.1 交集方法

1.内连接

select A.Store_Name from store_info A inner join location B on A.Store_Name=B.Store_Name;
select A.Store_Name from store_info A inner join location B using(Store_Name);

2.左连接

select B.Store_Name from location A left join store_info B on A.Store_Name=B.Store_Name where B.Store_Name is not null;

3.右连接

select A.Store_Name from location A right join store_info B on A.Store_Name=B.Store_Name where A.Store_Name is not null;

4.子查询

select A.Store_Name from store_info A where A.Store_Name in (select B.Store_Name from location B);
select A.Store_Name from store_info A where exists (select B.Store_Name from location B where A.Store_Name=B.Store_Name));

5.多表查询

select A.Store_Name from store_info A, location B where 
A.Store_Name=B.Store_Name;

6.联集+分组

select A.Store_Name from (select distinct Store_Name from store_info union all select distinct store_name from location) A group by A.Store_Name having count(A.Store_Name) > 1;

5.2 求无交集方法总结

求左表无交集

select A.Store_Name from location A left join store_info B on A.Store_Name=B.Store_Name where B.Store_Name is null;

select Store_Name from location where Store_Name not in (select Store_Name from store_info);

select A.Store_Name from location A where not exists (sellect B.Store_Name from store_info B where A.Store_Name=B.Store_NName);

求右表无交集

select B.Store_Name from location A right join store_info B on A.Store_Name=B.Store_Name where A.Store_Name is null;

select Store_Name from store_info where Store_Name not in (select Store_Name from location);

select A.Store_Name from store_info A where not exists (sselect B.Store_Name from location B where A.Store_Name=B.Store_NName);

求两个表无交集

select A.Store_Name from location A left join store_info B on A.Store_Name=B.Store_Name where B.Store_Name is null
    -> union all
    -> select B.Store_Name from location A right join store_infoo B on A.Store_Name=B.Store_Name where A.Store_Name is null;

select A.Store_Name from (select distinct Store_Name from store_info union all select distinct store_name from location) A group by A.Store_Name having count(A.Store_Name) = 1;