mysql高级语句（一）（总有一个人的出现，让你的生活不再继续糟糕）

企业开发 2022-06-05 23:46:25 阅读次数: 0

目录

前言

mysql高级SQL语句主要学习select语句

本章主要三个板块：

  1. mysql进阶查询
  2. mysql数据库函数
  3. mysql存储过程
#准备实验所需的两张表
use stevelu;
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');
mysql> select * from location ;
+--------+-------------+
| region | store_name  |
+--------+-------------+
| East   | Boston      |
| East   | New York    |
| West   | Los Angeles |
| West   | Houstion    |
+--------+-------------+

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');
mysql> select * from store_info;
+-------------+-------+------------+
| Store_Name  | Sales | Date       |
+-------------+-------+------------+
| Los Angeles |  1500 | 2020-12-05 |
| Houston     |   250 | 2020-12-07 |
| Los Angeles |   300 | 2020-12-08 |
| Boston      |   700 | 2020-12-08 |
+-------------+-------+------------+

一、mysql进阶查询（1）

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";

#查询表中的指定字段
mysql> SELECT Store_Name FROM store_info;
+-------------+
| Store_Name  |
+-------------+
| Los Angeles |
| Houston     |
| Los Angeles |
| Boston      |
+-------------+

#查询时可以把字段重新排序
mysql> select date,Store_Name,Sales from store_info;
+------------+-------------+-------+
| date       | Store_Name  | Sales |
+------------+-------------+-------+
| 2020-12-05 | Los Angeles |  1500 |
| 2020-12-07 | Houston     |   250 |
| 2020-12-08 | Los Angeles |   300 |
| 2020-12-08 | Boston      |   700 |
+------------+-------------+-------+

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1.2 DISTINCT

---- DISTINCT ----不显示重复的数据记录
语法：SELECT DISTINCT "字段" FROM "表名";

#不显示重复记录（DISTINCT加在字段前面）
mysql> SELECT DISTINCT Store_Name FROM store_info;
+-------------+
| Store_Name  |
+-------------+
| Los Angeles |
| Houston     |
| Boston      |
+-------------+
mysql> SELECT DISTINCT Store_Name,date FROM store_info;
+-------------+------------+
| Store_Name  | date       |
+-------------+------------+
| Los Angeles | 2020-12-05 |
| Houston     | 2020-12-07 |
| Los Angeles | 2020-12-08 |
| Boston      | 2020-12-08 |
+-------------+------------+

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1.3 WHERE

---- WHERE ----有条件查询
语法：SELECT "字段" FROM "表名" WHERE "条件";

#查询Store_Name为Houston的记录
mysql> select * from store_info where Store_Name='Houston';
+------------+-------+------------+
| Store_Name | Sales | Date       |
+------------+-------+------------+
| Houston    |   250 | 2020-12-07 |
+------------+-------+------------+

#查询Sales大于1000的Store_Name
mysql> SELECT Store_Name FROM store_info WHERE Sales > 1000;
+-------------+
| Store_Name  |
+-------------+
| Los Angeles |
+-------------+

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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"}+ ;
#查询sales大于500小于1000的store_name
mysql> select store_name from store_info where sales >500 and sales <1000;
+------------+
| store_name |
+------------+
| Boston     |
+------------+
#查看sales大于200小于500，或者大于1000，且和或同时有记得加括号，把括号里面作为一个整体优先看待
mysql> select store_name,sales from store_info where (sales >200 and sales <500) or sales>1000;
+-------------+-------+
| store_name  | sales |
+-------------+-------+
| Los Angeles |  1500 |
| Houston     |   250 |
| Los Angeles |   300 |
+-------------+-------+

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1.5 IN

---- IN ----显示已知的值的数据记录
#括号里面的值作为一个池子，有匹配该字段的就显示（值要用单引号）
语法：SELECT "字段" FROM "表名" WHERE "字段" IN ('值1', '值2', ...);
#查询Store_Name等于'Los Angeles'或 'Houston'
mysql> SELECT * FROM store_info WHERE Store_Name IN ('Los Angeles', 'Houston');
+-------------+-------+------------+
| Store_Name  | Sales | Date       |
+-------------+-------+------------+
| Los Angeles |  1500 | 2020-12-05 |
| Houston     |   250 | 2020-12-07 |
| Los Angeles |   300 | 2020-12-08 |
+-------------+-------+------------+
3 rows in set (0.00 sec)

#查询Store_Name不等于'Los Angeles'或 'Houston' （与上述操作取反）
mysql> SELECT * FROM store_info WHERE Store_Name not IN ('Los Angeles', 'Houston');
+------------+-------+------------+
| Store_Name | Sales | Date       |
+------------+-------+------------+
| Boston     |   700 | 2020-12-08 |
+------------+-------+------------+
1 row in set (0.00 sec)

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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';（数值左小右大）
#查询date在'2020-12-06' 和 '2020-12-10'之间的记录
mysql> SELECT * FROM store_info WHERE Date BETWEEN '2020-12-06' AND '2020-12-10';
+-------------+-------+------------+
| Store_Name  | Sales | Date       |
+-------------+-------+------------+
| Houston     |   250 | 2020-12-07 |
| Los Angeles |   300 | 2020-12-08 |
| Boston      |   700 | 2020-12-08 |
+-------------+-------+------------+
3 rows in set (0.00 sec)

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1.7 通配符与like

----通配符----通常通配符都是跟 LIKE 一起使用的（与Linux的通配符不同）
---- 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 '%os%';
% ：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。


#查询以on结尾的Store_Name的记录
mysql> select * from store_info where store_name like '%on';
+------------+-------+------------+
| Store_Name | Sales | Date       |
+------------+-------+------------+
| Houston    |   250 | 2020-12-07 |
| Boston     |   700 | 2020-12-08 |
+------------+-------+------------+
2 rows in set (0.00 sec)

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1.7 ORDER BY

---- ORDER BY ----按关键字排序（通常是对数值排序）
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。

#对Sales值降序排序
mysql> SELECT Store_Name,Sales,Date FROM store_info ORDER BY Sales DESC;
+-------------+-------+------------+
| Store_Name  | Sales | Date       |
+-------------+-------+------------+
| Los Angeles |  1500 | 2020-12-05 |
| Boston      |   700 | 2020-12-08 |
| Los Angeles |   300 | 2020-12-08 |
| Houston     |   250 | 2020-12-07 |
+-------------+-------+------------+
4 rows in set (0.00 sec)

#对store_name值的字母升序排序
mysql> select * from store_info order by store_name;
+-------------+-------+------------+
| Store_Name  | Sales | Date       |
+-------------+-------+------------+
| Boston      |   700 | 2020-12-08 |
| Houston     |   250 | 2020-12-07 |
| Los Angeles |  1500 | 2020-12-05 |
| Los Angeles |   300 | 2020-12-08 |
+-------------+-------+------------+
4 rows in set (0.00 sec)

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二、函数

2.1 数学函数

数学函数 含义
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
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，也可以返回多个字段的最大的值
least(x1,x2…) 返回集合中最小的值，也可以返回多个字段的最小的值 
#只能对数值进行操作
mysql> SELECT abs(-1), rand(), mod(5,3), power(2,3), round(1.89);
+---------+--------------------+----------+------------+-------------+
| abs(-1) | rand()             | mod(5,3) | power(2,3) | round(1.89) |
+---------+--------------------+----------+------------+-------------+
|       1 | 0.2744006926886744 |        2 |          8 |           2 |
+---------+--------------------+----------+------------+-------------+

mysql> SELECT round(1.8937,3), truncate(1.235,2), ceil(5.2), floor(2.1), least(1.89,3,6.1,2.1);
+-----------------+-------------------+-----------+------------+-----------------------+
| round(1.8937,3) | truncate(1.235,2) | ceil(5.2) | floor(2.1) | least(1.89,3,6.1,2.1) |
+-----------------+-------------------+-----------+------------+-----------------------+
|           1.894 |              1.23 |         6 |          2 |                  1.89 |
+-----------------+-------------------+-----------+------------+-----------------------+
#对member表生成随机排序
mysql> select * from member order by rand();
+----+----------+--------+--------+---------+--------------------+
| id | name     | cardid | phone  | address | remark             |
+----+----------+--------+--------+---------+--------------------+
|  1 | zhangsan | 123123 | 123123 | nanjing | this is vip        |
|  3 | wangwu   | 123123 | 123123 | wuxi    | this is vvvip      |
|  4 | zhaoliu  | 123123 | 123123 | nantong | this is vip member |
|  2 | lisi     | 123123 | 123123 | suzhou  | this is vvip       |
+----+----------+--------+--------+---------+--------------------+
4 rows in set (0.00 sec)

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2.2 聚合函数

聚合函数 含义
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(x) 返回指定列的所有值之和 
#查询表中sales最大的
mysql> select max(sales) from store_info;
+------------+
| max(sales) |
+------------+
|       1500 |
+------------+
1 row in set (0.00 sec)

#查询表中sales最小的
mysql> select min(sales) from store_info;
+------------+
| min(sales) |
+------------+
|        250 |
+------------+
1 row in set (0.00 sec)

#也可以结合排序找最小值或者最大值
mysql> select sales from store_info order by sales asc limit 1;
+-------+
| sales |
+-------+
|   250 |
+-------+

#查询sales的平均值
mysql> select avg(sales) from store_info;
+------------+
| avg(sales) |
+------------+
|   687.5000 |
+------------+
1 row in set (0.00 sec)

#求sales值的和
mysql> select sum(sales) from store_info;
+------------+
| sum(sales) |
+------------+
|       2750 |
+------------+
1 row in set (0.00 sec)

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新建一个city表，用来演示count()函数

create table city (name char(20));
insert into city values('nanjing');
insert into city values('hangzhou');
insert into city values('shanghai');
insert into city values();
insert into city values();
insert into city values('beijing');
insert into city values();
insert into city values();

#查询city表中的个数时，不会把空的记录算进去
mysql> select count(name) from city;
+-------------+
| count(name) |
+-------------+
|           4 |
+-------------+
#查询个数时，打上*，就不会忽略空行
mysql> select count(*) from city;
+----------+
| count(*) |
+----------+
|        8 |
+----------+

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2.3 字符串函数

字符串函数 含义
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

返回去除指定格式的值

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。

mysql> SELECT TRIM(LEADING 'Ne' FROM 'New York');
+------------------------------------+
| TRIM(LEADING 'Ne' FROM 'New York') |
+------------------------------------+
| w York                             |
+------------------------------------+
1 row in set (0.00 sec)

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将提供的参数 x 和 y 拼接成一个字符串

mysql> select concat('zhang','san');
+-----------------------+
| concat('zhang','san') |
+-----------------------+
| zhangsan              |
+-----------------------+
---在zhangsan中间加个空格，就是添加一个空格字符串
mysql> select concat('zhang',' ','san');
+---------------------------+
| concat('zhang',' ','san') |
+---------------------------+
| zhang san                 |
+---------------------------+

mysql> select * from location;
+--------+-------------+
| region | store_name  |
+--------+-------------+
| East   | Boston      |
| East   | New York    |
| West   | Los Angeles |
| West   | Houstion    |
+--------+-------------+
4 rows in set (0.00 sec)
---对location表中的两个字段进行合并，注意不要加引号
mysql> select concat(region,store_name) from location;
+---------------------------+
| concat(region,store_name) |
+---------------------------+
| EastBoston                |
| EastNew York              |
| WestLos Angeles           |
| WestHoustion              |
+---------------------------+
4 rows in set (0.00 sec)

---如sql_mode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
SELECT Region || ' ' || Store_Name FROM location

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获取从字符串 x 中的第 y 个位置开始长度为 z 的字符串

mysql> SELECT substr(concat(region,store_name),5) FROM location;
+-------------------------------------+
| substr(concat(region,store_name),5) |
+-------------------------------------+
| Boston                              |
| New York                            |
| Los Angeles                         |
| Houstion                            |
+-------------------------------------+
4 rows in set (0.00 sec)
---只显示Angele
mysql> SELECT substr(store_name,5,6) FROM location where store_name='Los Angeles';
+------------------------+
| substr(store_name,5,6) |
+------------------------+
| Angele                 |
+------------------------+
1 row in set (0.00 sec)

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返回字符串 x 的长度

mysql> select store_name,length(store_name) from location;
+-------------+--------------------+
| store_name  | length(store_name) |
+-------------+--------------------+
| Boston      |                  6 |
| New York    |                  8 |
| Los Angeles |                 11 |
| Houstion    |                  8 |
+-------------+--------------------+
4 rows in set (0.00 sec)

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将字符串 z 替代字符串 x 中的字符串 y

mysql> select replace(region,'st','stern') from location;
+------------------------------+
| replace(region,'st','stern') |
+------------------------------+
| Eastern                      |
| Eastern                      |
| Western                      |
| Western                      |
+------------------------------+
4 rows in set (0.00 sec)

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三、mysql进阶查询（2）

3.1 GROUP BY

对GROUP BY后面的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；

GROUP BY 有一个原则，凡是在 GROUP BY 后面出现的字段，必须在 SELECT 后面出现；

凡是在 SELECT 后面出现的、且未在聚合函数中出现的字段，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";
---对store_name进行分组，并对sales降序排序
mysql> SELECT store_name, SUM(Sales) FROM store_info GROUP BY store_name ORDER BY SUM(Sales) desc;
+-------------+------------+
| store_name  | SUM(Sales) |
+-------------+------------+
| Los Angeles |       1800 |
| Boston      |        700 |
| Houston     |        250 |
+-------------+------------+
3 rows in set (0.00 sec)

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3.2 HAVING

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。

语法：SELECT "字段1", SUM("字段2") FROM "表格名" GROUP BY "字段1" HAVING (函数条件);
mysql> SELECT store_name, SUM(Sales) FROM store_info GROUP BY store_name having sum(sales)>1000;
+-------------+------------+
| store_name  | SUM(Sales) |
+-------------+------------+
| Los Angeles |       1800 |
+-------------+------------+

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3.3 别名

语法：SELECT "表格別名"."字段1" [AS] "字段別名" FROM "表格名" [AS] "表格別名";
---字段设置别名
mysql> SELECT store_name, SUM(Sales) as total FROM store_info GROUP BY store_name having sum(sales)>1000;
+-------------+-------+
| store_name  | total |
+-------------+-------+
| Los Angeles |  1800 |
+-------------+-------+
1 row in set (0.00 sec)
---表别名
mysql> SELECT store_name, SUM(Sales) FROM store_info as a GROUP BY a.store_name ;
+-------------+------------+
| store_name  | SUM(Sales) |
+-------------+------------+
| Boston      |        700 |
| Houston     |        250 |
| Los Angeles |       1800 |
+-------------+------------+
3 rows in set (0.00 sec)

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3.4 表的自我连接

---通过对分数排名
mysql> select * from student;
+------+----------+-------+
| id   | name     | score |
+------+----------+-------+
|    1 | zhangsan |    70 |
|    2 | lisi     |   100 |
|    3 | wangwu   |    80 |
|    4 | zhaoliu  |    90 |
+------+----------+-------+
mysql> select A.name,A.score,count(A.score) rank from student as A,student as B where A.score<=B.score group by A.name,A.score order by rank asc;
+----------+-------+------+
| name     | score | rank |
+----------+-------+------+
| lisi     |   100 |    1 |
| zhaoliu  |    90 |    2 |
| wangwu   |    80 |    3 |
| zhangsan |    70 |    4 |
+----------+-------+------+
4 rows in set (0.00 sec)

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3.5 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

---多表连接
mysql> select * from store_info A, location B where A.store_name=B.store_name;
+-------------+-------+------------+--------+-------------+
| Store_Name  | Sales | Date       | region | store_name  |
+-------------+-------+------------+--------+-------------+
| Boston      |   700 | 2020-12-08 | East   | Boston      |
| Los Angeles |  1500 | 2020-12-05 | West   | Los Angeles |
| Los Angeles |   300 | 2020-12-08 | West   | Los Angeles |
+-------------+-------+------------+--------+-------------+
3 rows in set (0.00 sec)

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mysql> select * from store_info;
+-------------+-------+------------+
| Store_Name  | Sales | Date       |
+-------------+-------+------------+
| Los Angeles |  1500 | 2020-12-05 |
| Houston     |   250 | 2020-12-07 |
| Los Angeles |   300 | 2020-12-08 |
| Boston      |   700 | 2020-12-08 |
+-------------+-------+------------+
4 rows in set (0.01 sec)

mysql> select store_name from location where region='west';
+-------------+
| store_name  |
+-------------+
| Los Angeles |
| Houstion    |
+-------------+
2 rows in set (0.00 sec)

mysql> select sum(sales) from store_info where store_name in (select store_name from location where region='west');
+------------+
| sum(sales) |
+------------+
|       1800 |
+------------+
1 row in set (0.00 sec)

在这里插入图片描述

3.6 EXISTS

用来测试内查询有没有产生任何结果，类似布尔值是否为真

#如果有的话，系统就会执行外查询中的SQL语句。若是没有的话，那整个 SQL 语句就不会产生任何结果。
语法：SELECT "字段1" FROM "表格1" WHERE EXISTS (SELECT * FROM "表格2" WHERE "条件");
mysql> select sum(sales) from store_info where exists(select * from location where region = 'west');
+------------+
| sum(sales) |
+------------+
|       2750 |
+------------+
1 row in set (0.00 sec)

mysql> select sum(sales) from store_info where exists(select * from location where region = 'westeee');
+------------+
| sum(sales) |
+------------+
|       NULL |
+------------+
1 row in set (0.00 sec)

在这里插入图片描述

3.7 连接查询

  1. inner join(内连接):只返回两个表中联结字段相等的行
  2. left join(左连接):返回包括左表中的所有记录和石表中联结字段相等的记录
  3. 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

3.7.1 inner join(内连接)

 #连接两个表中字段记录相等的数据记录
 方法一:
 select * from location A inner join store_info B on A.store_name=B.store_name;
 方法二:
 select * from location A, store_info B where A.store_name=B.store_name;
 #连接两个表内字段数据记录相等的数据记录对region字段进行汇总分组并求和
select A.region region,sum(B.sales) sales from location A,store_info B where A.store_name = B.store_name group by region;

在这里插入图片描述

在这里插入图片描述

在这里插入图片描述

3.7.2 left join(左连接)

mysql> select * from location A LEFT JOIN store_info B on A.store_name=B.store_name;
+--------+-------------+-------------+-------+------------+
| Region | Store_Name  | Store_Name  | Sales | Date       |
+--------+-------------+-------------+-------+------------+
| East   | Boston      | Boston      |   700 | 2020-12-08 |
| East   | New York    | NULL        |  NULL | NULL       |
| West   | Los Angeles | Los Angeles |  1500 | 2020-12-05 |
| West   | Los Angeles | Los Angeles |   300 | 2020-12-08 |
| West   | Houston     | Houston     |   250 | 2020-12-07 |
+--------+-------------+-------------+-------+------------+
5 rows in set (0.01 sec)

在这里插入图片描述

3.7.3 right join(右连接)

mysql> select * from location A RIGHT JOIN store_info B on A.store_name=B.store_name;
+--------+-------------+-------------+-------+------------+
| Region | Store_Name  | Store_Name  | Sales | Date       |
+--------+-------------+-------------+-------+------------+
| West   | Los Angeles | Los Angeles |  1500 | 2020-12-05 |
| West   | Houston     | Houston     |   250 | 2020-12-07 |
| West   | Los Angeles | Los Angeles |   300 | 2020-12-08 |
| East   | Boston      | Boston      |   700 | 2020-12-08 |
| NULL   | NULL        | lll         |   758 | 2020-12-10 |
+--------+-------------+-------------+-------+------------+
5 rows in set (0.00 sec)

在这里插入图片描述

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