MySQL入门（参考官网）

一、登陆和退出

1. 远程主机

shell> mysql -h host -u user -p
Enter password: ********
Welcome to the MySQL monitor.  Commands end with ; or \g.

mysql>

2. 登陆本机

shell> mysql -u user -p

3. 退出mysql

mysql> QUIT

二、输入查询

查询版本号和当前日期

mysql> SELECT VERSION(), CURRENT_DATE;
+-----------+--------------+
| VERSION() | CURRENT_DATE |
+-----------+--------------+
| 5.7.24    | 2018-11-12   |
+-----------+--------------+
1 row in set (0.01 sec)

mysql>

大小写不敏感

把mysql当计算器用

mysql> SELECT SIN(PI()/4), (4+1)*5;
+--------------------+---------+
| SIN(PI()/4)        | (4+1)*5 |
+--------------------+---------+
| 0.7071067811865476 |      25 |
+--------------------+---------+
1 row in set (0.01 sec)

在一行上输入多个语句。分号结束每一个命令:

mysql> SELECT VERSION(); SELECT NOW();
+-----------+
| VERSION() |
+-----------+
| 5.7.24    |
+-----------+
1 row in set (0.00 sec)

+---------------------+
| NOW()               |
+---------------------+
| 2018-11-13 00:10:14 |
+---------------------+
1 row in set (0.00 sec)

mysql 通过 查找终止分号;来确定语句的结束位置

mysql> SELECT
    -> USER()
    -> ,
    -> CURRENT_DATE;
+----------------+--------------+
| USER()         | CURRENT_DATE |
+----------------+--------------+
| root@localhost | 2018-11-13   |
+----------------+--------------+
1 row in set (0.00 sec)

mysql> SELECT USER(),CURRENT_DATE;
+----------------+--------------+
| USER()         | CURRENT_DATE |
+----------------+--------------+
| root@localhost | 2018-11-13   |
+----------------+--------------+
1 row in set (0.00 sec)

通过键入以下内容取消该查询:\c

mysql> SELECT
    -> USER()
    -> \c

三、创建和使用数据库

展示存在的数据库

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| falcon             |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

使用数据库

mysql> USE test
Database changed

shell> mysql -h host -u user -p menagerie
Enter password: ********

3.1 创建和选择数据库

mysql> CREATE DATABASE menagerie;

mysql> USE menagerie
Database changed

3.2 创建表

mysql> SHOW TABLES;
Empty set (0.00 sec)

创建表

mysql> CREATE TABLE pet (name VARCHAR(20), owner VARCHAR(20),
    -> species VARCHAR(20), sex CHAR(1), birth DATE, death DATE);

展示表单：

mysql> SHOW TABLES;
+---------------------+
| Tables_in_menagerie |
+---------------------+
| pet                 |
+---------------------+
1 row in set (0.00 sec)

描述表单

mysql> DESCRIBE pet;
+---------+-------------+------+-----+---------+-------+
| Field   | Type        | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| name    | varchar(20) | YES  |     | NULL    |       |
| owner   | varchar(20) | YES  |     | NULL    |       |
| species | varchar(20) | YES  |     | NULL    |       |
| sex     | char(1)     | YES  |     | NULL    |       |
| birth   | date        | YES  |     | NULL    |       |
| death   | date        | YES  |     | NULL    |       |
+---------+-------------+------+-----+---------+-------+
6 rows in set (0.01 sec)

3.3 将数据加载到表中

建立表格以后需要：

• 导入数据：LOAD DATA
• 插入数据：INSERT

name	owner	species	sex	birth	death
Fluffy	Harold	cat	f	1993-02-04
Claws	Gwen	cat	m	1994-03-17
Buffy	Harold	dog	f	1989-05-13
Fang	Benny	dog	m	1990-08-27
Bowser	Diane	dog	m	1979-08-31	1995-07-29
Chirpy	Gwen	bird	f	1998-09-11
Whistler	Gwen	bird		1997-12-09
Slim	Benny	snake	m	1996-04-29

保存为pet.txt

从excel中直接复制到pet.txt,空值用\N 表示

Whistler        Gwen    bird    \N      1997-12-09      \N

3.3.1 导入数据

LOAD DATA LOCAL INFILE 'D:/Temp/pet.txt' INTO TABLE pet;

win编辑器

mysql> LOAD DATA LOCAL INFILE '/path/pet.txt' INTO TABLE pet
    -> LINES TERMINATED BY '\r\n';

在运行 os x 的 apple 计算机上, 您可能想要使用。LINES TERMINATED BY '\r'

3.3.2 插入语句

mysql> INSERT INTO pet
    -> VALUES ('Puffball','Diane','hamster','f','1999-03-30',NULL);

3.4 操作表格

SELECT 语法：

SELECT what_to_select
FROM which_table
WHERE conditions_to_satisfy;

3.4.1 查询所有数据

mysql> SELECT * FROM pet;
+----------+--------+---------+------+------------+------------+
| name     | owner  | species | sex  | birth      | death      |
+----------+--------+---------+------+------------+------------+
| Fluffy   | Harold | cat     | f    | 1993-02-04 | NULL       |
| Claws    | Gwen   | cat     | m    | 1994-03-17 | NULL       |
| Buffy    | Harold | dog     | f    | 1989-05-13 | NULL       |
| Fang     | Benny  | dog     | m    | 1990-08-27 | NULL       |
| Bowser   | Diane  | dog     | m    | 1979-08-31 | 1995-07-29 |
| Chirpy   | Gwen   | bird    | f    | 1998-09-11 | NULL       |
| Whistler | Gwen   | bird    | NULL | 1997-12-09 | NULL       |
| Slim     | Benny  | snake   | m    | 1996-04-29 | NULL       |
| Puffball | Diane  | hamster | f    | 1999-03-30 | NULL       |
+----------+--------+---------+------+------------+------------+

update 语句修复错误记录 :

mysql> UPDATE pet SET birth = '1989-08-31' WHERE name = 'Bowser';

3.4.2 查询某行

选择特定行:

mysql> SELECT * FROM pet WHERE name = 'Bowser';
+--------+-------+---------+------+------------+------------+
| name   | owner | species | sex  | birth      | death      |
+--------+-------+---------+------+------------+------------+
| Bowser | Diane | dog     | m    | 1989-08-31 | 1995-07-29 |
+--------+-------+---------+------+------------+------------+

选择特定条件：

mysql>  SELECT * FROM pet WHERE birth >= '1998-1-1';
+----------+-------+---------+------+------------+------------+
| name     | owner | species | sex  | birth      | death      |
+----------+-------+---------+------+------------+------------+
| Chirpy   | Gwen  | bird    | f    | 1998-09-11 | 0000-00-00 |
| Puffball | Diane | hamster | f    | 1999-03-30 | NULL       |
+----------+-------+---------+------+------------+------------+

条件and：

mysql> SELECT * FROM pet WHERE species = 'dog' AND sex = 'f';
+-------+--------+---------+------+------------+------------+
| name  | owner  | species | sex  | birth      | death      |
+-------+--------+---------+------+------------+------------+
| Buffy | Harold | dog     | f    | 1989-05-13 | 0000-00-00 |
+-------+--------+---------+------+------------+------------+

条件or：

mysql> SELECT * FROM pet WHERE species = 'snake' OR species = 'bird';
+----------+-------+---------+------+------------+------------+
| name     | owner | species | sex  | birth      | death      |
+----------+-------+---------+------+------------+------------+
| Chirpy   | Gwen  | bird    | f    | 1998-09-11 | 0000-00-00 |
| Whistler | Gwen  | bird    |      | 1997-12-09 | 0000-00-00 |
| Slim     | Benny | snake   | m    | 1996-04-29 | 0000-00-00 |
+----------+-------+---------+------+------------+------------+

and 、 or 混合使用：

mysql> SELECT * FROM pet WHERE (species = 'cat' AND sex = 'm')
    -> OR (species = 'dog' AND sex = 'f');
+-------+--------+---------+------+------------+------------+
| name  | owner  | species | sex  | birth      | death      |
+-------+--------+---------+------+------------+------------+
| Claws | Gwen   | cat     | m    | 1994-03-17 | 0000-00-00 |
| Buffy | Harold | dog     | f    | 1989-05-13 | 0000-00-00 |
+-------+--------+---------+------+------------+------------+

3.4.3 查询某列

选择某列，按照 ，分隔

mysql> SELECT name`,` birth FROM pet;
+----------+------------+   
| name     | birth      |
+----------+------------+
| name     | 0000-00-00 |
| Fluffy   | 1993-02-04 |
| Claws    | 1994-03-17 |
| Buffy    | 1989-05-13 |
| Fang     | 1990-08-27 |
| Bowser   | 1989-08-31 |
| Chirpy   | 1998-09-11 |
| Whistler | 1997-12-09 |
| Slim     | 1996-04-29 |
| Puffball | 1999-03-30 |
+----------+------------+

选择动物主人：

mysql> SELECT owner FROM pet;
+--------+
| owner  |
+--------+
| owner  |
| Harold |
| Gwen   |
| Harold |
| Benny  |
| Diane  |
| Gwen   |
| Gwen   |
| Benny  |
| Diane  |
+--------+

使用DISTINCT去重

mysql> SELECT DISTINCT owner FROM pet;
+--------+
| owner  |
+--------+
| owner  |
| Harold |
| Gwen   |
| Benny  |
| Diane  |
+--------+

使用WHERE条件查询

mysql> SELECT name, species, birth FROM pet
    -> WHERE species = 'dog' OR species = 'cat';
+--------+---------+------------+
| name   | species | birth      |
+--------+---------+------------+
| Fluffy | cat     | 1993-02-04 |
| Claws  | cat     | 1994-03-17 |
| Buffy  | dog     | 1989-05-13 |
| Fang   | dog     | 1990-08-27 |
| Bowser | dog     | 1989-08-31 |
+--------+---------+------------+

3.4.4 排序行

使用ORDER BY ,默认升序

mysql>  SELECT name, birth FROM pet ORDER BY birth;
+----------+------------+
| name     | birth      |
+----------+------------+
| name     | 0000-00-00 |
| Buffy    | 1989-05-13 |
| Bowser   | 1989-08-31 |
| Fang     | 1990-08-27 |
| Fluffy   | 1993-02-04 |
| Claws    | 1994-03-17 |
| Slim     | 1996-04-29 |
| Whistler | 1997-12-09 |
| Chirpy   | 1998-09-11 |
| Puffball | 1999-03-30 |
+----------+------------+

默认不区分大小写排序，如果要区分使用：

ORDER BY BINARY col_name

BINARY：转换为二进制字符,方便排序

使用ORDER BY ,默认升序，如果降序，添加DESC

mysql> SELECT name, birth FROM pet ORDER BY birth DESC;
+----------+------------+
| name     | birth      |
+----------+------------+
| Puffball | 1999-03-30 |
| Chirpy   | 1998-09-11 |
| Whistler | 1997-12-09 |
| Slim     | 1996-04-29 |
| Claws    | 1994-03-17 |
| Fluffy   | 1993-02-04 |
| Fang     | 1990-08-27 |
| Bowser   | 1989-08-31 |
| Buffy    | 1989-05-13 |
| name     | 0000-00-00 |
+----------+------------+

多个列排序：

先按照动物种类升序，然后按照出生日期降序

mysql> SELECT name, species, birth FROM pet
    -> ORDER BY species, birth DESC;


+----------+---------+------------+
| name     | species | birth      |
+----------+---------+------------+
| Chirpy   | bird    | 1998-09-11 |
| Whistler | bird    | 1997-12-09 |
| Claws    | cat     | 1994-03-17 |
| Fluffy   | cat     | 1993-02-04 |
| Fang     | dog     | 1990-08-27 |
| Bowser   | dog     | 1989-08-31 |
| Buffy    | dog     | 1989-05-13 |
| Puffball | hamster | 1999-03-30 |
| Slim     | snake   | 1996-04-29 |
| name     | species | 0000-00-00 |
+----------+---------+------------+

3.4.5 ‎日期计算

TIMESTAMPDIFF()：时间差函数

mysql> SELECT TIMESTAMPDIFF(YEAR,'1989-08-31',CURDATE());
+--------------------------------------------+
| TIMESTAMPDIFF(YEAR,'1989-08-31',CURDATE()) |
+--------------------------------------------+
|                                         29 |
+--------------------------------------------+

常用时间函数：

mysql> SELECT NOW(),CURDATE(),CURTIME();
+---------------------+------------+-----------+
| NOW()               | CURDATE()  | CURTIME() |
+---------------------+------------+-----------+
| 2018-11-13 10:21:28 | 2018-11-13 | 10:21:28  |
+---------------------+------------+-----------+

查询显示每个宠物的出生日期、当前日期，用age做别名

mysql> SELECT name, birth, CURDATE(),
    -> TIMESTAMPDIFF(YEAR,birth,CURDATE()) AS age
    -> FROM pet;
+----------+------------+------------+------+
| name     | birth      | CURDATE()  | age  |
+----------+------------+------------+------+
| Fluffy   | 1993-02-04 | 2018-11-13 |   25 |
| Claws    | 1994-03-17 | 2018-11-13 |   24 |
| Buffy    | 1989-05-13 | 2018-11-13 |   29 |
| Fang     | 1990-08-27 | 2018-11-13 |   28 |
| Bowser   | 1989-08-31 | 2018-11-13 |   29 |
| Chirpy   | 1998-09-11 | 2018-11-13 |   20 |
| Whistler | 1997-12-09 | 2018-11-13 |   20 |
| Slim     | 1996-04-29 | 2018-11-13 |   22 |
| Puffball | 1999-03-30 | 2018-11-13 |   19 |
+----------+------------+------------+------+

查询同时 按照姓名排序

mysql> SELECT name, birth, CURDATE(),
    -> TIMESTAMPDIFF(YEAR,birth,CURDATE()) AS age
    -> FROM pet ORDER BY name;
+----------+------------+------------+------+
| name     | birth      | CURDATE()  | age  |
+----------+------------+------------+------+
| Bowser   | 1989-08-31 | 2018-11-13 |   29 |
| Buffy    | 1989-05-13 | 2018-11-13 |   29 |
| Chirpy   | 1998-09-11 | 2018-11-13 |   20 |
| Claws    | 1994-03-17 | 2018-11-13 |   24 |
| Fang     | 1990-08-27 | 2018-11-13 |   28 |
| Fluffy   | 1993-02-04 | 2018-11-13 |   25 |
| Puffball | 1999-03-30 | 2018-11-13 |   19 |
| Slim     | 1996-04-29 | 2018-11-13 |   22 |
| Whistler | 1997-12-09 | 2018-11-13 |   20 |
+----------+------------+------------+------+

查询同时 按照年龄排序

mysql> SELECT name, birth, CURDATE(),
    -> TIMESTAMPDIFF(YEAR,birth,CURDATE()) AS age
    -> FROM pet ORDER BY age;
+----------+------------+------------+------+
| name     | birth      | CURDATE()  | age  |
+----------+------------+------------+------+
| Puffball | 1999-03-30 | 2018-11-13 |   19 |
| Chirpy   | 1998-09-11 | 2018-11-13 |   20 |
| Whistler | 1997-12-09 | 2018-11-13 |   20 |
| Slim     | 1996-04-29 | 2018-11-13 |   22 |
| Claws    | 1994-03-17 | 2018-11-13 |   24 |
| Fluffy   | 1993-02-04 | 2018-11-13 |   25 |
| Fang     | 1990-08-27 | 2018-11-13 |   28 |
| Buffy    | 1989-05-13 | 2018-11-13 |   29 |
| Bowser   | 1989-08-31 | 2018-11-13 |   29 |
+----------+------------+------------+------+

查询已经死亡的宠物

把默认导入的数值从'0000-00-00' 改成'NUll'

关于NULL

UPDATE pet SET death = NULL WHERE death= 0000-00-00;

mysql> SELECT name, birth, death,
    -> TIMESTAMPDIFF(YEAR,birth,death) AS age
    -> FROM pet WHERE death IS NOT NULL ORDER BY age;
+--------+------------+------------+------+
| name   | birth      | death      | age  |
+--------+------------+------------+------+
| Bowser | 1989-08-31 | 1995-07-29 |    5 |
+--------+------------+------------+------+

MySQL 的一些日期函数：

• YEAR()：返回年

• MONTH()：返回月

• DAYOFMONTH()：返回日

• DATE_ADD() ：添加时间
  ​

mysql> SELECT YEAR('1987-01-01');
+--------------------+
| YEAR('1987-01-01') |
+--------------------+
|               1987 |
+--------------------+

mysql> SELECT MONTH('2008-02-03');
+---------------------+
| MONTH('2008-02-03') |
+---------------------+
|                   2 |
+---------------------+

mysql> SELECT MONTHNAME('2008-02-03');
+-------------------------+
| MONTHNAME('2008-02-03') |
+-------------------------+
| February                |
+-------------------------+

现在是今年的 多少天 多少周

mysql> SELECT DAYOFYEAR(now()),WEEKOFYEAR(now());
+------------------+-------------------+
| DAYOFYEAR(now()) | WEEKOFYEAR(now()) |
+------------------+-------------------+
|              317 |                46 |
+------------------+-------------------+

2008-01-03第多少天，多少周

mysql> SELECT DAYOFYEAR('2008-01-03'),WEEKOFYEAR('2008-01-03');
+-------------------------+--------------------------+
| DAYOFYEAR('2008-01-03') | WEEKOFYEAR('2008-01-03') |
+-------------------------+--------------------------+
|                       3 |                        1 |
+-------------------------+--------------------------+

查询宠物出生月

mysql> SELECT name, birth, MONTH(birth) FROM pet;
+----------+------------+--------------+
| name     | birth      | MONTH(birth) |
+----------+------------+--------------+
| Fluffy   | 1993-02-04 |            2 |
| Claws    | 1994-03-17 |            3 |
| Buffy    | 1989-05-13 |            5 |
| Fang     | 1990-08-27 |            8 |
| Bowser   | 1989-08-31 |            8 |
| Chirpy   | 1998-09-11 |            9 |
| Whistler | 1997-12-09 |           12 |
| Slim     | 1996-04-29 |            4 |
| Puffball | 1999-03-30 |            3 |
+----------+------------+--------------+

查询5月出生的宠物

mysql> SELECT name, birth FROM pet WHERE MONTH(birth) = 5;
+-------+------------+
| name  | birth      |
+-------+------------+
| Buffy | 1989-05-13 |
+-------+------------+

2018-05-01 添加1天

mysql> SELECT DATE_ADD('2018-05-01',INTERVAL 1 DAY);
+---------------------------------------+
| DATE_ADD('2018-05-01',INTERVAL 1 DAY) |
+---------------------------------------+
| 2018-05-02                            |
+---------------------------------------+

查询下个月是哪个月

mysql> SELECT  MONTH(DATE_ADD(CURDATE(),INTERVAL 1 MONTH));
+---------------------------------------------+
| MONTH(DATE_ADD(CURDATE(),INTERVAL 1 MONTH)) |
+---------------------------------------------+
|                                          12 |
+---------------------------------------------+

查询即将生日的宠物，距离目前最近的一个月

• 方法1：当前月份+1个月

mysql> SELECT name, birth FROM pet
    ->  WHERE MONTH(birth) = MONTH(DATE_ADD(CURDATE(),INTERVAL 1 MONTH));
+----------+------------+
| name     | birth      |
+----------+------------+
| Whistler | 1997-12-09 |
+----------+------------+

• 方法2：当前月份取余+1

mysql> SELECT name, birth FROM pet
    -> WHERE MONTH(birth) = MOD(MONTH(CURDATE()), 12) + 1;
+----------+------------+
| name     | birth      |
+----------+------------+
| Whistler | 1997-12-09 |
+----------+------------+

• MOD(12, 5)

mysql> SELECT MOD(12, 5);
+------------+
| MOD(12, 5) |
+------------+
|          2 |
+------------+

3.4.6 使用空值

NULL value ：a missing unknown value，要和其他值区别对待

测试NULL，使用

• IS NULL
• IS NOT NULL

mysql> SELECT 1 IS NULL, 1 IS NOT NULL;
+-----------+---------------+
| 1 IS NULL | 1 IS NOT NULL |
+-----------+---------------+
|         0 |             1 |
+-----------+---------------+

mysql> SELECT 0 IS NULL, 0 IS NOT NULL, '' IS NULL, '' IS NOT NULL;
+-----------+---------------+------------+----------------+
| 0 IS NULL | 0 IS NOT NULL | '' IS NULL | '' IS NOT NULL |
+-----------+---------------+------------+----------------+
|         0 |             1 |          0 |              1 |
+-----------+---------------+------------+----------------+

不能使用算术笔记用算符判断null

=, <, or <>

3.4.7 匹配方式

1. 标准的 sql 模式匹配
2. 正则表达式的模式匹配
3. 默认不区分大小写

标准匹配

使用：

• LIKE

• NOT LIKE

查找b开头的名字：

mysql> SELECT * FROM pet WHERE name LIKE 'b%';
+--------+--------+---------+------+------------+------------+
| name   | owner  | species | sex  | birth      | death      |
+--------+--------+---------+------+------------+------------+
| Buffy  | Harold | dog     | f    | 1989-05-13 | NULL       |
| Bowser | Diane  | dog     | m    | 1989-08-31 | 1995-07-29 |
+--------+--------+---------+------+------------+------------+

查找fy结尾的名字：

mysql> SELECT * FROM pet WHERE name LIKE '%fy';
+--------+--------+---------+------+------------+-------+
| name   | owner  | species | sex  | birth      | death |
+--------+--------+---------+------+------------+-------+
| Fluffy | Harold | cat     | f    | 1993-02-04 | NULL  |
| Buffy  | Harold | dog     | f    | 1989-05-13 | NULL  |

查找名字包含一个w:

mysql> SELECT * FROM pet WHERE name LIKE '%w%';
+----------+-------+---------+------+------------+------------+
| name     | owner | species | sex  | birth      | death      |
+----------+-------+---------+------+------------+------------+
| Claws    | Gwen  | cat     | m    | 1994-03-17 | NULL       |
| Bowser   | Diane | dog     | m    | 1989-08-31 | 1995-07-29 |
| Whistler | Gwen  | bird    | NULL | 1997-12-09 | NULL       |
+----------+-------+---------+------+------------+------------+

查找名字是5个字符的：

mysql> SELECT * FROM pet WHERE name LIKE '_____';
+-------+--------+---------+------+------------+-------+
| name  | owner  | species | sex  | birth      | death |
+-------+--------+---------+------+------------+-------+
| Claws | Gwen   | cat     | m    | 1994-03-17 | NULL  |
| Buffy | Harold | dog     | f    | 1989-05-13 | NULL  |
+-------+--------+---------+------+------------+-------+

正则匹配

使用：

• REGEXP
• NOT REGEXP

RLIKE NOT RLIKE 和上述等价

查找b开头的名字：

mysql> SELECT * FROM pet WHERE name REGEXP '^b';
+--------+--------+---------+------+------------+------------+
| name   | owner  | species | sex  | birth      | death      |
+--------+--------+---------+------+------------+------------+
| Buffy  | Harold | dog     | f    | 1989-05-13 | NULL       |
| Bowser | Diane  | dog     | m    | 1989-08-31 | 1995-07-29 |
+--------+--------+---------+------+------------+------------+

若要强制 regexp 比较区分大小写, 请使用 binary 关键字将其中一个字符串设置为二进制字符串。

匹配名称由小写:b开头

SELECT * FROM pet WHERE name REGEXP BINARY '^b';

查找fy结尾的名字：

mysql> SELECT * FROM pet WHERE name REGEXP 'fy$';
+--------+--------+---------+------+------------+-------+
| name   | owner  | species | sex  | birth      | death |
+--------+--------+---------+------+------------+-------+
| Fluffy | Harold | cat     | f    | 1993-02-04 | NULL  |
| Buffy  | Harold | dog     | f    | 1989-05-13 | NULL  |
+--------+--------+---------+------+------------+-------+

查找名字包含一个w:

mysql> SELECT * FROM pet WHERE name REGEXP 'w';
+----------+-------+---------+------+------------+------------+
| name     | owner | species | sex  | birth      | death      |
+----------+-------+---------+------+------------+------------+
| Claws    | Gwen  | cat     | m    | 1994-03-17 | NULL       |
| Bowser   | Diane | dog     | m    | 1989-08-31 | 1995-07-29 |
| Whistler | Gwen  | bird    | NULL | 1997-12-09 | NULL       |
+----------+-------+---------+------+------------+------------+

查找名字是5个字符的

mysql> SELECT * FROM pet WHERE name REGEXP '^.....$';
+-------+--------+---------+------+------------+-------+
| name  | owner  | species | sex  | birth      | death |
+-------+--------+---------+------+------------+-------+
| Claws | Gwen   | cat     | m    | 1994-03-17 | NULL  |
| Buffy | Harold | dog     | f    | 1989-05-13 | NULL  |
+-------+--------+---------+------+------------+-------+

或者^.{5}$ ：^开头$结尾

mysql> SELECT * FROM pet WHERE name REGEXP '^.{5}$';
+-------+--------+---------+------+------------+-------+
| name  | owner  | species | sex  | birth      | death |
+-------+--------+---------+------+------------+-------+
| Claws | Gwen   | cat     | m    | 1994-03-17 | NULL  |
| Buffy | Harold | dog     | f    | 1989-05-13 | NULL  |
+-------+--------+---------+------+------------+-------+

3.4.8 统计行

COUNT(*) 统计函数

统计行数

mysql> SELECT COUNT(*) FROM pet;
+----------+
| COUNT(*) |
+----------+
|        9 |
+----------+

统计每个人有多少只宠物

mysql>  SELECT owner, COUNT(*) FROM pet GROUP BY owner;
+--------+----------+
| owner  | COUNT(*) |
+--------+----------+
| Benny  |        2 |
| Diane  |        2 |
| Gwen   |        3 |
| Harold |        2 |
+--------+----------+

统计每种动物的数量：

mysql> SELECT species, COUNT(*) FROM pet GROUP BY species;
+---------+----------+
| species | COUNT(*) |
+---------+----------+
| bird    |        2 |
| cat     |        2 |
| dog     |        3 |
| hamster |        1 |
| snake   |        1 |

统计物种性别：

mysql> SELECT sex, COUNT(*) FROM pet GROUP BY sex;
+------+----------+
| sex  | COUNT(*) |
+------+----------+
| NULL |        1 |
| f    |        4 |
| m    |        4 |
+------+----------+

物种和性别的组合：

mysql> SELECT species, sex, COUNT(*) FROM pet GROUP BY species, sex;
+---------+------+----------+
| species | sex  | COUNT(*) |
+---------+------+----------+
| bird    | NULL |        1 |
| bird    | f    |        1 |
| cat     | f    |        1 |
| cat     | m    |        1 |
| dog     | f    |        1 |
| dog     | m    |        2 |
| hamster | f    |        1 |
| snake   | m    |        1 |
+---------+------+----------+

只针对某个字段筛选，不用筛选整行

选择cat 和 dog种类，按照性别物种组合

mysql> SELECT species, sex, COUNT(*) FROM pet
    -> WHERE species = 'dog' OR species = 'cat'
    -> GROUP BY species, sex;
+---------+------+----------+
| species | sex  | COUNT(*) |
+---------+------+----------+
| cat     | f    |        1 |
| cat     | m    |        1 |
| dog     | f    |        1 |
| dog     | m    |        2 |
+---------+------+----------+

列出已知动物性别：

mysql> SELECT species, sex, COUNT(*) FROM pet
    -> WHERE sex IS NOT NULL
    -> GROUP BY species, sex;
+---------+------+----------+
| species | sex  | COUNT(*) |
+---------+------+----------+
| bird    | f    |        1 |
| cat     | f    |        1 |
| cat     | m    |        1 |
| dog     | f    |        1 |
| dog     | m    |        2 |
| hamster | f    |        1 |
| snake   | m    |        1 |
+---------+------+----------+

ONLY_FULL_GROUP_BY

mysql> SET sql_mode = 'ONLY_FULL_GROUP_BY';-- 启用

mysql> SELECT owner, COUNT(*) FROM pet;
ERROR 1140 (42000):

ONLY_FULL_GROUP_BY 关闭后，结果不确定，系统随意添加一个值，最好关闭

mysql> SET sql_mode = '';   -- 关闭
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT owner, COUNT(*) FROM pet;
+--------+----------+
| owner  | COUNT(*) |
+--------+----------+
| Harold |        9 |
+--------+----------+


mysql> SELECT owner, COUNT(*) FROM pet GROUP BY owner;
+--------+----------+
| owner  | COUNT(*) |
+--------+----------+
| Benny  |        2 |
| Diane  |        2 |
| Gwen   |        3 |
| Harold |        2 |
+--------+----------+

3.4.9 使用多个表

此表格跟踪记录你的宠物，当你想记录他们的信息，比如看兽医、生幼崽、买玩具等事件，就需要另外一个表单记录，需要如下信息：

• 宠物名称：name
• 事件日期：date
• 事件类型：type
• 事件描述：emark

CREATE ABLE

创建表一个符合上述要素的表单:

mysql> CREATE TABLE event (name VARCHAR(20), date DATE,
    -> type VARCHAR(15), remark VARCHAR(255));

将下述内容存储为event.txt

name	date	type	remark
Fluffy	1995-05-15	litter	4 kittens, 3 female, 1 male
Buffy	1993-06-23	litter	5 puppies, 2 female, 3 male
Buffy	1994-06-19	litter	3 puppies, 3 female
Chirpy	1999-03-21	vet	needed beak straightened
Slim	1997-08-03	vet	broken rib
Bowser	1991-10-12	kennel
Fang	1991-10-12	kennel
Fang	1998-08-28	birthday	Gave him a new chew toy
Claws	1998-03-17	birthday	Gave him a new flea collar
Whistler	1998-12-09	birthday	First birthday

导入内容到表单

mysql> LOAD DATA LOCAL INFILE 'event.txt' INTO TABLE event;

假设：想知道每个宠物下崽时的年龄，宠物妈妈下崽时间在event表单，但是，出生日期在pet表单，所以要同时查询2个表单。

mysql> SELECT pet.name,
    -> TIMESTAMPDIFF(YEAR,birth,date) AS age,
    -> remark
    -> FROM pet INNER JOIN event
    ->   ON pet.name = event.name
    -> WHERE event.type = 'litter';
+--------+------+------------------------------+
| name   | age  | remark                       |
+--------+------+------------------------------+
 |Fluffy |    2 | 4 kittens, 3 female, 1 male
 |Buffy  |    4 | 5 puppies, 2 female, 3 male
         |    5 | 3 puppies, 3 female
+--------+------+------------------------------+

jion表单:

• 是为从两张表获取信息
• 需要指定匹配规则，上述例子都有'name'
• 需要指定前缀ON pet.name = event.name

表的自身连接

宠物的雌雄配对：

mysql> SELECT p1.name, p1.sex, p2.name, p2.sex, p1.species
    -> FROM pet AS p1 INNER JOIN pet AS p2
    ->    ON p1.species = p2.species AND p1.sex = 'f' AND p2.sex = 'm';
+--------+------+--------+------+---------+
| name   | sex  | name   | sex  | species |
+--------+------+--------+------+---------+
| Fluffy | f    | Claws  | m    | cat     |
| Buffy  | f    | Fang   | m    | dog     |
| Buffy  | f    | Bowser | m    | dog     |
+--------+------+--------+------+---------+

3.4 获取数据库和表的信息

• SHOW DATABASES
• DATABASE()

查看目前使用的数据库

mysql> SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| menagerie  |
+------------+

查看表

mysql> SHOW TABLES;
+---------------------+
| Tables_in_menagerie |
+---------------------+
| event               |
| pet                 |
+---------------------+

查看表结构

mysql> DESCRIBE pet;
+---------+-------------+------+-----+---------+-------+
| Field   | Type        | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| name    | varchar(20) | YES  |     | NULL    |       |
| owner   | varchar(20) | YES  |     | NULL    |       |
| species | varchar(20) | YES  |     | NULL    |       |
| sex     | char(1)     | YES  |     | NULL    |       |
| birth   | date        | YES  |     | NULL    |       |
| death   | date        | YES  |     | NULL    |       |
+---------+-------------+------+-----+---------+-------+

3.5 批处理模式

在mysql内运行脚本：

mysql> source filename;
mysql> \. filename

来源：MySQL官网