MySQL高级（进阶）SQL语句

• MySQL高级（进阶）SQL语句
  • 一、实例准备--制表
    • 1. 表一（商店区域表）
    • 2. 表2（商店销售表）
    • 3. 表3（城市表）
  • 二、SQL查询/匹配/排序语句
    • 1. select
    • 2. distinct
    • 3. where
    • 4. and|or
    • 5. in
    • 6. between
    • 7. limit
    • 8. 通配符
    • 9. like
    • 10. order by
  • 三、函数
    • 1. 数学函数
      • （1）abs(x)
      • （2）rand()
      • （3）mod（x,y）
      • （4）power(x,y)
      • （5）round(x)
      • （6）round(x,y)
      • （7）sqrt(x)
      • （8）truncate(x,y)
      • （9）ceil(x)
      • （10）floor(x)
      • （11）greatest(x1,x2...)
      • （12）least(x1,x2...)
    • 2. 聚合函数
      • （1）avg()
      • （2）count()
      • （3）min()
      • （4）max()
      • （5）sum()
    • 3. 字符串函数
      • （1）trim()
      • （2）concat(x,y)
      • （3）substr(x,y)
      • （4）substr(x,y,z)
      • （5）length(x)
      • （6）replace(x,y,z)
      • （7）upper(x)
      • （8）lower(x)
      • （9）left(x,y)
      • （10）right(x,y)
      • （11）reprat(x,y)
      • （12）space(x)
      • （13）strcmp(x,y)
      • （14）reverse(x)
  • 四、分组
    • 1. group by
    • 2. having
  • 五、别名
  • 六、子查询

一、实例准备--制表

1. 表一（商店区域表）

[root@localhost ~]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.20-log Source distribution

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> create table location (region char(20),store_name char(20));
Query OK, 0 rows affected (0.01 sec)

mysql> insert into location values('North','Beijing');
Query OK, 1 row affected (0.00 sec)

mysql> insert into location values('Eaet','shanghai');
Query OK, 1 row affected (0.00 sec)

mysql> insert into location values('South','Guangzhou');
Query OK, 1 row affected (0.00 sec)

mysql> insert into location values('South','Shenzhen');
Query OK, 1 row affected (0.01 sec)

mysql> select * from location;
+--------+------------+
| region | store_name |
+--------+------------+
| North  | Beijing    |
| East   | Shanghai   |
| South  | Guangzhou  |
| South  | Shenzhen   |
+--------+------------+
4 rows in set (0.00 sec)

2. 表2（商店销售表）

mysql> create table store_info (store_name char(20),sales int(10),date char(10));
Query OK, 0 rows affected (0.00 sec)

mysql> insert into store_info values('Guangzhou',1500,'2020-12-05');
Query OK, 1 row affected (0.00 sec)

mysql> insert into store_info values('Shenzhen',250,'2020-12-07');
Query OK, 1 row affected (0.00 sec)

mysql> insert into store_info values('Guangzhou',300,'2020-12-08');
Query OK, 1 row affected (0.00 sec)

mysql> insert into store_info values('Beijing',700,'2020-12-08');
Query OK, 1 row affected (0.00 sec)

mysql> select * from store_info;
+------------+-------+------------+
| store_name | sales | date       |
+------------+-------+------------+
| Guangzhou  |  1500 | 2020-12-05 |
| Shenzhen   |   250 | 2020-12-07 |
| Guangzhou  |   300 | 2020-12-08 |
| Beijing    |   700 | 2020-12-08 |
+------------+-------+------------+
4 rows in set (0.00 sec)

3. 表3（城市表）

mysql> create table city(city_name char(20));
Query OK, 0 rows affected (0.00 sec)

mysql> insert into city values('beijing'),('nanjing'),('shanghai');
Query OK, 3 rows affected (0.01 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> insert into city values();
Query OK, 1 row affected (0.00 sec)

mysql> insert into city values();
Query OK, 1 row affected (0.00 sec)

mysql> select * from city;
+-----------+
| city_name |
+-----------+
| beijing   |
| nanjing   |
| shanghai  |
| NULL      |
| NULL      |
+-----------+
5 rows in set (0.00 sec)

二、SQL查询/匹配/排序语句

1. select

显示表格中一个或数个栏位的所有资料
语法：select "栏位" from "表名";

mysql> select store_name from store_info;
+------------+
| store_name |
+------------+
| Guangzhou  |
| Shenzhen   |
| Guangzhou  |
| Beijing    |
+------------+
4 rows in set (0.00 sec)

2. distinct

不显示重复的资料
语法：select dstinct "栏位" from "表名";

mysql> select distinct store_name from store_info;
+------------+
| store_name |
+------------+
| Guangzhou  |
| Shenzhen   |
| Beijing    |
+------------+
3 rows in set (0.00 sec)

3. where

有条件查询
语法：select "栏位" from "表名" where "条件";

mysql> select store_name from store_info where sales>1000;
+------------+
| store_name |
+------------+
| Guangzhou  |
+------------+
1 row in set (0.00 sec)

4. and|or

且、或
语法：select "栏位" from "表名" where "条件1" {[and|or] “条件2”}...;

mysql> select store_name from store_info where sales>1000 or (sales<500 and sales>200);
+------------+
| store_name |
+------------+
| Guangzhou  |
| Shenzhen   |
| Guangzhou  |
+------------+
3 rows in set (0.00 sec)

5. in

显示已知的值的资料
语法：select "栏位" from "表名" where "栏位" in ("值1","值2",...);

mysql> select * from store_info where store_name in ('Beijing','Shenzhen');
+------------+-------+------------+
| store_name | sales | date       |
+------------+-------+------------+
| Shenzhen   |   250 | 2020-12-07 |
| Beijing    |   700 | 2020-12-08 |
+------------+-------+------------+
2 rows in set (0.00 sec)

6. between

显示两个值范围内的资料
语法：select "栏位" from "表名" where "栏位" between '值1' and '值2';

mysql> select * from store_info where date between '2020-12-06' and '2020-12-10';
+------------+-------+------------+
| store_name | sales | date       |
+------------+-------+------------+
| Shenzhen   |   250 | 2020-12-07 |
| Guangzhou  |   300 | 2020-12-08 |
| Beijing    |   700 | 2020-12-08 |
+------------+-------+------------+
3 rows in set (0.00 sec)

7. limit

（1）显示前几行内容
语法：select "栏位" from "表名" limit '行数';

mysql> select * from store_info limit 2;
+------------+-------+------------+
| store_name | sales | date       |
+------------+-------+------------+
| Guangzhou  |  1500 | 2020-12-05 |
| Shenzhen   |   250 | 2020-12-07 |
+------------+-------+------------+
2 rows in set (0.00 sec)

（2）显示第几行后的前几行
语法：select "栏位" from "表名" limit "第几行后,显示行数";

mysql> select * from store_info limit 2,2;
+------------+-------+------------+
| store_name | sales | date       |
+------------+-------+------------+
| Guangzhou  |   300 | 2020-12-08 |
| Beijing    |   700 | 2020-12-08 |
+------------+-------+------------+
2 rows in set (0.00 sec)

8. 通配符

通常通配符都是跟like一起使用的

例如：
'A-Z'
表示所有以'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'ABCZ'并不符合（因为A和Z之间有两个字符，而不是一个字符）
'ABC%'
表示所有以'ABC'起头的字符串。例如，'ABCD'和'ABCABC'都符合这个模式。
'%XYZ'
表示所有以'XYZ'结尾的字符串。例如，'WXYZ'和'ZZXYZ'都符合这个模式。
'%AN%'
表示所有含有'AN'这个模式的字符串。例如，'SHANGHAI'和'XIAN'都符合这个模式。
'_AN%'
表示第二个字母为'A'且第三个字母为'N'的字符串。例如，'HANGZHOU'和'LANZHOU'都符合这个模式，而'SHANGHAI'和'XIAN'则不符合这个模式。

9. like

匹配一个模式来搜查资料
语法：select "栏位" from “表名” where "栏位" like {模式};

mysql> select * from store_info where store_name like '%e%';
+------------+-------+------------+
| store_name | sales | date       |
+------------+-------+------------+
| Shenzhen   |   250 | 2020-12-07 |
| Beijing    |   700 | 2020-12-08 |
+------------+-------+------------+
2 rows in set (0.00 sec)

10. order by

按关键字排序
语法：select "栏位" from “表名” [where "条件"] order by "栏位" [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。

mysql> select store_name,sales,date from store_info order by sales desc;
+------------+-------+------------+
| store_name | sales | date       |
+------------+-------+------------+
| Guangzhou  |  1500 | 2020-12-05 |
| Beijing    |   700 | 2020-12-08 |
| Guangzhou  |   300 | 2020-12-08 |
| Shenzhen   |   250 | 2020-12-07 |
+------------+-------+------------+
4 rows in set (0.00 sec)

三、函数

1. 数学函数

（1）abs(x)

返回x的绝对值

mysql> select abs(-2.3);
+-----------+
| abs(-2.3) |
+-----------+
|       2.3 |
+-----------+
1 row in set (0.00 sec)

（2）rand()

返回0-1的随机数

mysql> select rand();
+--------------------+
| rand()             |
+--------------------+
| 0.1262695352791525 |
+--------------------+
1 row in set (0.00 sec)

（3）mod（x,y）

返回x除以y以后的余数

mysql> select mod(5,2);
+----------+
| mod(5,2) |
+----------+
|        1 |
+----------+
1 row in set (0.00 sec)

（4）power(x,y)

返回x的y次方

mysql> select power(2,8);
+------------+
| power(2,8) |
+------------+
|        256 |
+------------+
1 row in set (0.00 sec)

（5）round(x)

返回离x最近的整数,即四舍五入到个位

mysql> select round(3.1415);
+---------------+
| round(3.1415) |
+---------------+
|             3 |
+---------------+
1 row in set (0.00 sec)

mysql> select round(3.5415);
+---------------+
| round(3.5415) |
+---------------+
|             4 |
+---------------+
1 row in set (0.00 sec)

（6）round(x,y)

返回x的y位小数且四舍五入后的值

mysql> select round(3.1415,2);
+-----------------+
| round(3.1415,2) |
+-----------------+
|            3.14 |
+-----------------+
1 row in set (0.00 sec)

mysql> select round(3.1415,3);
+-----------------+
| round(3.1415,3) |
+-----------------+
|           3.142 |
+-----------------+
1 row in set (0.00 sec)

（7）sqrt(x)

返回x的平方根

mysql> select sqrt(9);
+---------+
| sqrt(9) |
+---------+
|       3 |
+---------+
1 row in set (0.00 sec)

mysql> select sqrt(8);
+--------------------+
| sqrt(8)            |
+--------------------+
| 2.8284271247461903 |
+--------------------+
1 row in set (0.00 sec)

（8）truncate(x,y)

返回数字X截断为y位小数的值

mysql> select truncate(3.1415,2);
+--------------------+
| truncate(3.1415,2) |
+--------------------+
|               3.14 |
+--------------------+
1 row in set (0.00 sec)

mysql> select truncate(3.1415,3);
+--------------------+
| truncate(3.1415,3) |
+--------------------+
|              3.141 |
+--------------------+
1 row in set (0.00 sec)

（9）ceil(x)

返回大于或等于x的最小整数

mysql> select ceil(3.1415);
+--------------+
| ceil(3.1415) |
+--------------+
|            4 |
+--------------+
1 row in set (0.00 sec)

（10）floor(x)

返回小于或等于x的最大整数

mysql> select floor(3.1415);
+---------------+
| floor(3.1415) |
+---------------+
|             3 |
+---------------+
1 row in set (0.00 sec)

（11）greatest(x1,x2...)

返回集合中最大的值

mysql> select greatest(3.1415,3,4,5.2);
+--------------------------+
| greatest(3.1415,3,4,5.2) |
+--------------------------+
|                   5.2000 |
+--------------------------+
1 row in set (0.00 sec)

（12）least(x1,x2...)

返回集合中最小的值

mysql> select least(3.1415,3,4,5.2);
+-----------------------+
| least(3.1415,3,4,5.2) |
+-----------------------+
|                3.0000 |
+-----------------------+
1 row in set (0.00 sec)

2. 聚合函数

（1）avg()

返回指定列的平均值

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

（2）count()

1. 返回指定列中非NULL值的个数

mysql> select count(store_name) from store_info;
+-------------------+
| count(store_name) |
+-------------------+
|                 4 |
+-------------------+
1 row in set (0.00 sec)

2. 返回指定列中非NULL值且去重的个数

mysql> select count(distinct store_name) from store_info;
+----------------------------+
| count(distinct store_name) |
+----------------------------+
|                          3 |
+----------------------------+
1 row in set (0.00 sec)

3. count()
   count()包括了所有的列的行数，在统计结果的时候，不会忽略值为NULL的行

mysql> select count(*) from city;
+----------+
| count(*) |
+----------+
|        5 |
+----------+
1 row in set (0.00 sec)

4. count("列名")
   count("列名")只包括列名那一列的行数，在统计结果的时候，会忽略值为NULL的行

mysql> select count(city_name) from city;
+------------------+
| count(city_name) |
+------------------+
|                3 |
+------------------+
1 row in set (0.00 sec)

（3）min()

返回指定列的最小值

mysql> select min(sales) from store_info;
+------------+
| min(sales) |
+------------+
|        250 |
+------------+
1 row in set (0.01 sec)

（4）max()

返回指定列的最大值

mysql> select max(sales) from store_info;
+------------+
| max(sales) |
+------------+
|       1500 |
+------------+
1 row in set (0.00 sec)

（5）sum()

返回指定列的所有值之和

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

3. 字符串函数

（1）trim()

返回去除指定格式的值
语法：select trim([[位置] [要移除的字符串] from] 字符串);
[位置]：该值可以为leading（起头），trailing（结尾），both（起头及结尾）。缺省时为both。
[要移除的字符串]：从字串的起头、结尾，或起头即结尾移除的字符串。缺省时为空格。

mysql> select trim('g' from 'guangdong');
+----------------------------+
| trim('g' from 'guangdong') |
+----------------------------+
| uangdon                    |
+----------------------------+
1 row in set (0.00 sec)

mysql> select trim(leading 'g' from 'guangdong');
+------------------------------------+
| trim(leading 'g' from 'guangdong') |
+------------------------------------+
| uangdong                           |
+------------------------------------+
1 row in set (0.00 sec)

mysql> select trim(trailing 'g' from 'guangdong');
+-------------------------------------+
| trim(trailing 'g' from 'guangdong') |
+-------------------------------------+
| guangdon                            |
+-------------------------------------+
1 row in set (0.00 sec)

mysql> select trim(both 'g' from 'guangdong');
+---------------------------------+
| trim(both 'g' from 'guangdong') |
+---------------------------------+
| uangdon                         |
+---------------------------------+
1 row in set (0.00 sec)

（2）concat(x,y)

将提供的参数x和y拼接成一个字符串

mysql> select concat (region,' ',store_name) from location where store_name='Beeijing';
+--------------------------------+
| concat (region,' ',store_name) |
+--------------------------------+
| North Beijing                  |
+--------------------------------+
1 row in set (0.00 sec)

如sql_mode开启了PIPES_AS_CONCAT（可使用"select @@SESSION.sql_mode;"或"select @@GLOBAL.sql_mode;"进行查看），"||"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相类似，这和Oracle数据库使用方法一样。

mysql> select store_name || ' ' || sales from store_info where store_name='Guanngzhou';
+----------------------------+
| store_name || ' ' || sales |
+----------------------------+
| Guangzhou 1500             |
| Guangzhou 300              |
+----------------------------+
2 rows in set (0.00 sec)

（3）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

mysql> select substr(store_name,3) from location where store_name='Guangzhou'; 
+----------------------+
| substr(store_name,3) |
+----------------------+
| angzhou              |
+----------------------+
1 row in set (0.00 sec)

（4）substr(x,y,z)

获取从字符串x中第y个位置开始长度为z的字符串

mysql> select substr(store_name,3,4) from location where store_name='Guangzhou'';
+------------------------+
| substr(store_name,3,4) |
+------------------------+
| angz                   |
+------------------------+
1 row in set (0.00 sec)

（5）length(x)

返回字符串x的长度

mysql> select *,length(store_name) from location;
+--------+------------+--------------------+
| region | store_name | length(store_name) |
+--------+------------+--------------------+
| North  | Beijing    |                  7 |
| East   | Shanghai   |                  8 |
| South  | Guangzhou  |                  9 |
| South  | Shenzhen   |                  8 |
+--------+------------+--------------------+
4 rows in set (0.00 sec)

（6）replace(x,y,z)

将字符串z替代字符串x中的字符串y

mysql> select replace(store_name,'ng','xx') from location;
+-------------------------------+
| replace(store_name,'ng','xx') |
+-------------------------------+
| Beijixx                       |
| Shaxxhai                      |
| Guaxxzhou                     |
| Shenzhen                      |
+-------------------------------+
4 rows in set (0.00 sec)

（7）upper(x)

将字符串x的所有字母变成大写字符

mysql> select upper(store_name) from location;
+-------------------+
| upper(store_name) |
+-------------------+
| BEIJING           |
| SHANGHAI          |
| GUANGZHOU         |
| SHENZHEN          |
+-------------------+
4 rows in set (0.00 sec)

（8）lower(x)

将字符串x的所有字母变成小写字符

mysql> select lower(store_name) from location;
+-------------------+
| lower(store_name) |
+-------------------+
| beijing           |
| shanghai          |
| guangzhou         |
| shenzhen          |
+-------------------+
4 rows in set (0.00 sec)

（9）left(x,y)

返回字符串x的前y个字符

mysql> select left('Beijing',3);
+-------------------+
| left('Beijing',3) |
+-------------------+
| Bei               |
+-------------------+
1 row in set (0.00 sec)

（10）right(x,y)

返回字符串x的后y个字符

mysql> select right('Beijing',3);
+--------------------+
| right('Beijing',3) |
+--------------------+
| ing                |
+--------------------+
1 row in set (0.00 sec)

（11）reprat(x,y)

将字符串x重复y次

mysql> select repeat('Beijing ',3);
+--------------------------+
| repeat('Beijing ',3)     |
+--------------------------+
| Beijing Beijing Beijing  |
+--------------------------+
1 row in set (0.00 sec)

（12）space(x)

返回x个空格

mysql> select space(10);
+------------+
| space(10)  |
+------------+
|            |
+------------+
1 row in set (0.00 sec)

mysql> select space(15);
+-----------------+
| space(15)       |
+-----------------+
|                 |
+-----------------+
1 row in set (0.00 sec)

（13）strcmp(x,y)

比较x和y，返回的值可以为-1,0,1
x=y，返回0

mysql> select strcmp(1,1);
+-------------+
| strcmp(1,1) |
+-------------+
|           0 |
+-------------+
1 row in set (0.00 sec)

x<y，返回-1

mysql> select strcmp(1,2);
+-------------+
| strcmp(1,2) |
+-------------+
|          -1 |
+-------------+
1 row in set (0.00 sec)

x>y，返回1

mysql> select strcmp(2,1);
+-------------+
| strcmp(2,1) |
+-------------+
|           1 |
+-------------+
1 row in set (0.00 sec)

（14）reverse(x)

将字符串x反转

mysql> select reverse(sales) from store_info;
+----------------+
| reverse(sales) |
+----------------+
| 0051           |
| 052            |
| 003            |
| 007            |
+----------------+
4 rows in set (0.00 sec)

四、分组

1. group by

对group 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 "栏位1",sum("栏位2") from "表名" group by "栏位1";

mysql> select store_name,sum(sales) from store_info group by store_name order by sales desc;
+------------+------------+
| store_name | sum(sales) |
+------------+------------+
| Guangzhou  |       1800 |
| Beijing    |        700 |
| Shenzhen   |        250 |
+------------+------------+
3 rows in set (0.00 sec)

"Guangzhou"有两条属性信息，通过group by分组后，同名项将被合并，可通过以下方式确定是否有重名项以及重名次数。

mysql> select store_name,count(store_name),sum(sales) from store_info group by  store_name order by sales desc;
+------------+-------------------+------------+
| store_name | count(store_name) | sum(sales) |
+------------+-------------------+------------+
| Guangzhou  |                 2 |       1800 |
| Beijing    |                 1 |        700 |
| Shenzhen   |                 1 |        250 |
+------------+-------------------+------------+
3 rows in set (0.00 sec)

也可通过前后sales是否变化，判断是否有重名项被合并。

mysql> select store_name,sales,sum(sales) from store_info group by store_name order by sales desc;
+------------+-------+------------+
| store_name | sales | sum(sales) |
+------------+-------+------------+
| Guangzhou  |  1500 |       1800 |
| Beijing    |   700 |        700 |
| Shenzhen   |   250 |        250 |
+------------+-------+------------+
3 rows in set (0.00 sec)

2. 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 "栏位1",sum("栏位2") from "表名" group by “栏位1” having (函数条件);

mysql> select store_name,sum(sales) from store_info group by store_name having sum(sales)>1500;
+------------+------------+
| store_name | sum(sales) |
+------------+------------+
| Guangzhou  |       1800 |
+------------+------------+
1 row in set (0.00 sec)

五、别名

栏位别名/表格别名
语法：select "表格别名"."栏位1" [as] "栏位别名" from "表格名" [as] "表格别名";

mysql> select A.store_name as STORE,sum(A.sales) as 'TOTAL_SALES' from store_info as A group by STORE;
+-----------+-------------+
| STORE     | TOTAL_SALES |
+-----------+-------------+
| Beijing   |         700 |
| Guangzhou |        1800 |
| Shenzhen  |         250 |
+-----------+-------------+
3 rows in set (0.00 sec)

六、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：slect "栏位1" from "表格1" where "栏位2" [比较运算符] (select "栏位1" from "表格2" where "条件");
其中：
slect "栏位1" from "表格1" where "栏位2" [比较运算符] 为外查询，
(select "栏位1" from "表格2" where "条件")为内查询。
[比较运算符]可以是符号的运算符，例如=、>、<、>=、<=；也可以是文字的匹配符，例如like、in、between等。

mysql> select sum(sales) from store_info where store_name in (select store_name from location where region='North');
+------------+
| sum(sales) |
+------------+
|        700 |
+------------+
1 row in set (0.00 sec)

注：匹配两个表的列名可以不相同，但列中需有相同内容，否则将返回空值。

mysql> alter table location change store_name name char(20);
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> select sum(sales) from store_info where store_name in (select name from location where region='North');
+------------+
| sum(sales) |
+------------+
|        700 |
+------------+
1 row in set (0.00 sec)

mysql> select sum(sales) from store_info where sales in (select name from locattion where region='North');
+------------+
| sum(sales) |
+------------+
|       NULL |
+------------+
1 row in set, 4 warnings (0.00 sec)