mysql教程

本文轉載自查看原文 2016-03-01 20:48 4627 mysql 最新官方教程教材

1.查看mysql幫助信息

C:\Users\zhangcunli>mysql --help

mysql Ver 14.14 Distrib 5.7.9, for Win64 (x86_64)

Oracle is a registered trademark of Oracle Corporation and/or its

affiliates. Other names may be trademarks of their respective

owners.

Usage: mysql [OPTIONS] [database]

-?, --help Display this help and exit.

-I, --help Synonym for -?

--auto-rehash Enable automatic rehashing. One doesn't need to use

'rehash' to get table and field completion, but startup

and reconnecting may take a longer time. Disable with

--disable-auto-rehash.

2.鏈接mysql數據庫（服務）

方法一：

C:\Users\zhangcunli>mysql -h localhost -u cunli -p

Enter password: *****

Welcome to the MySQL monitor. Commands end with ; or \g.

Your MySQL connection id is 12

Server version: 5.7.9-log MySQL Community Server (GPL)

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>

方法二：

C:\Users\zhangcunli>mysql -u cunli -p

Enter password: *****

Welcome to the MySQL monitor. Commands end with ; or \g.

Your MySQL connection id is 13

Server version: 5.7.9-log MySQL Community Server (GPL)

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>

3.退出mysql數據庫（服務）

mysql> QUIT

Bye

4.查詢mysql當前版本和當前日期

mysql> SELECT VERSION(), CURRENT_DATE;

+-----------+--------------+

| VERSION() | CURRENT_DATE |

+-----------+--------------+

| 5.7.9-log | 2016-02-16 |

+-----------+--------------+

1 row in set (0.00 sec)

mysql>

5.mysql語句大小寫效果相同

mysql> SELECT VERSION(), CURRENT_DATE;
mysql> select version(), current_date;
mysql> SeLeCt vErSiOn(), current_DATE;

6.可以用mysql進行簡單的計算

mysql> SELECT SIN(PI()/4), (4+1)*5;

+--------------------+---------+

| SIN(PI()/4) | (4+1)*5 |

+--------------------+---------+

| 0.7071067811865476 | 25 |

+--------------------+---------+

1 row in set (0.14 sec)

7.可以把多條查詢語句放在一行執行，只要每行以分號結尾。

mysql> SELECT VERSION(); SELECT NOW();

+-----------+

| VERSION() |

+-----------+

| 5.7.9-log |

+-----------+

1 row in set (0.00 sec)

+---------------------+

| NOW() |

+---------------------+

| 2016-02-16 15:06:29 |

+---------------------+

1 row in set (0.00 sec)

一個簡單的多行聲明：

mysql> SELECT

-> USER()

-> ,

-> CURRENT_DATE;

+-----------------+--------------+

| USER() | CURRENT_DATE |

+-----------------+--------------+

| cunli@localhost | 2016-02-16 |

+-----------------+--------------+

1 row in set (0.00 sec)

8.如果你不想執行一條語句，你應該以\c結尾

mysql> SELECT

-> USER()

-> \c

9.各種提示的意思

Prompt	Meaning
`mysql>`	Ready for new query
`->`	Waiting for next line of multiple-line query
`'>`	Waiting for next line, waiting for completion of a string that began with a single quote (“`'`”)
`">`	Waiting for next line, waiting for completion of a string that began with a double quote (“`"`”)
`>	Waiting for next line, waiting for completion of an identifier that began with a backtick (“`”)
`/*>`	Waiting for next line, waiting for completion of a comment that began with `/*`

Prompt	Meaning
`mysql>`	准備執行一個查詢
`->`	等待多行輸入中的下一行輸入
`'>`	等待下一行輸入或等待輸入一個結束的單引號 (“`'`”)
`">`	等待下一行輸入或等待輸入一個結束的雙引號 (“`"`”)
`>	等待下一行輸入或等待輸入這個標識符結尾 (“`”)
`/*>`	等待下一行輸入或等待輸入一個結束的標識符`/*`

下面這種情況，MySQL正等待輸入

mysql> SELECT USER()

輸入一個分號，以完成這條聲明

mysql> SELECT USER()

-> ;

+-----------------+

| USER() |

+-----------------+

| cunli@localhost |

+-----------------+

1 row in set (0.00 sec)

當你看見 '> 或者 "> 標記的時候，意思是提示你，應該以單引號 ’ 或雙引號 “ 結尾，但是你還沒有結尾

mysql> SELECT * FROM my_table WHERE name='Smith AND age < 30;

這個時候，你該怎么辦呢？最簡單的，關閉這個查詢。但是，你不能只寫\c關閉，因為這時候，mysql會把他拆分成上個字符串的一部分。

你應該以缺少的標記 ‘ + \c 結束（ '\c ），這樣mysql就知道你要完成這個字符串。

mysql> SELECT * FROM my_table WHERE name='Smith AND age < 30;

'> '\c

mysql>

'\c 這個標記返回到了 mysql>, 這說明mysql准備好執行一個新的語句了。

創建和使用一個數據庫

10.用 SHOW 關鍵字找出當前mysql服務上已經存在的數據庫

mysql> SHOW DATABASES;

+--------------------+

| Database |

+--------------------+

| information_schema |

| know_yourself |

| menageria |

| mysql |

| performance_schema |

| sakila |

| sys |

| test |

| websystique |

| world |

+--------------------+

10 rows in set (0.00 sec)

11.進入並使用一個數據庫

mysql> USE test

Database changed

mysql>

USE 像 LIKE 一樣，不需要分號結尾，但是USE必須在單獨一行。

如果你能訪問一個數據庫，你就能使用這個數據庫，但是有時候，你創建的數據庫，如果別人也能訪問，他就可以刪除它。因此，你應該向你的數據庫管理員要一個你自己的數據庫。比如你的數據庫名字叫 menagerie，數據庫管理員需要執行以下申請

mysql> GRANT ALL ON menagerie.* TO 'your_mysql_name'@'your_client_host';

your_mysql_name 是訪問你數據庫的用戶名， your_client_host 是連接你數據庫服務的地址

創建和查詢一個數據庫

12.創建一個數據庫

mysql> CREATE DATABASE menagerie;

Query OK, 1 row affected (0.02 sec)

mysql>

13.選擇要使用的數據庫

mysql> USE menagerie

Database changed

14.直接進入指定的數據庫

C:\Users\zhangcunli>mysql -h localhost -u cunli -p menagerie

Enter password: *****

Welcome to the MySQL monitor. Commands end with ; or \g.

Your MySQL connection id is 16

Server version: 5.7.9-log MySQL Community Server (GPL)

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>

15.創建一張表

查詢當前數據中的所有表

mysql> show tables;

Empty set (0.00 sec)

創建一張pet表，有字段： name, owner, species, sex, birth, and death.

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

Query OK, 0 rows affected (0.39 sec)

再次查看當前數據庫中的表

mysql> show tables;

+---------------------+

| Tables_in_menagerie |

+---------------------+

| pet |

+---------------------+

1 row in set (0.00 sec)

可以用 DESCRIBE關鍵字核實你的表是否以你指定的方式創建成功。

mysql> DESCRIBE pet;

+---------+-------------+------+-----+---------+-------+

+---------+-------------+------+-----+---------+-------+

| sex | char(1) | YES | | NULL | |

+---------+-------------+------+-----+---------+-------+

6 rows in set (0.17 sec)

如果你忘記了你表中的列名或類型，你可以用 DESCRIBE關鍵字查看

16.你可以用 LOAD DATA and INSERT 關鍵字向表中添加數據

假設你的pet表信息如下：（注意MySQL認為日期的格式是 'YYYY-MM-DD' ，這可能和你常用的日期格式不同）

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

使用LOAD DATA 方式向表中添加數據

你應該創建一個pet.txt文件，保證每行一條數據。沒有值的字段用 \N 表示，如下：

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

按如下方式加載pet.txt到pet表中：

如果你是在windows系統上創建pet.txt文件，你應該在每行的結尾加上 \r\n , 就像下面這樣：

mysql> LOAD DATA LOCAL INFILE 'D:/100/pets.txt' INTO TABLE pet LINES TERMINATED BY '\r\n';

Query OK, 8 rows affected, 7 warnings (0.25 sec)

Records: 8 Deleted: 0 Skipped: 0 Warnings: 7

mysql> select * from pet;

+----------+--------+---------+------+------------+------------+

+----------+--------+---------+------+------------+------------+

| 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 |

+----------+--------+---------+------+------------+------------+

8 rows in set (0.00 sec)

你可以用 INSERT 關鍵字添加一條新數據，像下面這樣：

mysql> INSERT INTO pet VALUES ('Puffball','Diane','hamster','f','1990-03-30',NULL);

Query OK, 1 row affected (0.19 sec)

從一個表中檢索信息

17.SELECT 關鍵字是從一個表中檢索信息，順序是：

SELECT what_to_select
FROM which_table
WHERE conditions_to_satisfy;

what_to_select 是你想查詢的信息。 可以查詢其中的一列或用 * 查詢出所有的列。

查詢所有數據

18.下面這個例子使用SELECT查詢表中的所有信息

mysql> select * from pet;

+----------+--------+---------+------+------------+------------+

+----------+--------+---------+------+------------+------------+

| 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 |

+----------+--------+---------+------+------------+------------+

8 rows in set (0.00 sec)

刪除表中的所有數據

mysql> DELETE FROM pet;

Query OK, 9 rows affected (0.16 sec)

導入pet.txt到pet表中

mysql> load data local infile 'd:/100/pets.txt' INTO TABLE pet;

Query OK, 8 rows affected, 7 warnings (0.22 sec)

Records: 8 Deleted: 0 Skipped: 0 Warnings: 7

用UPDATE關鍵字可以修改其中一條錯誤

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

Query OK, 1 row affected (0.19 sec)

Rows matched: 1 Changed: 1 Warnings: 0

UDPATE 關鍵字只能更該一條數據

19.查詢特定的行

查詢名字叫Bowser動物的信息

mysql> SELECT * FROM pet WHERE name = 'Bowser';

+--------+-------+---------+------+------------+------------+

+--------+-------+---------+------+------------+------------+

| Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 |

+--------+-------+---------+------+------------+------------+

1 row in set (0.00 sec)

查詢生日大於1998-1-1的動物的信息

mysql> SELECT * FROM pet WHERE birth >= '1998-1-1';

+----------+-------+---------+------+------------+-------+

+----------+-------+---------+------+------------+-------+

+----------+-------+---------+------+------------+-------+

查詢種類是dog並且性別為f的動物的信息

mysql> SELECT * FROM pet WHERE species = 'dog' AND sex = 'f';

+-------+--------+---------+------+------------+-------+

+-------+--------+---------+------+------------+-------+

| Buffy | Harold | dog | f | 1989-05-13 | NULL |

+-------+--------+---------+------+------------+-------+

查詢種類是snake或者種類是bird的動物的信息

mysql> SELECT * FROM pet WHERE species = 'snake' OR species = 'bird';

+----------+-------+---------+------+------------+-------+

+----------+-------+---------+------+------------+-------+

+----------+-------+---------+------+------------+-------+

查詢種類是cat並且性別是m或者種類是dog並且性別是f的動物的信息

mysql> SELECT * FROM pet WHERE (species = 'cat' AND sex = 'm')

-> OR (species = 'dog' AND sex = 'f');

+-------+--------+---------+------+------------+-------+

+-------+--------+---------+------+------------+-------+

| Claws | Gwen | cat | m | 1994-03-17 | NULL |

| Buffy | Harold | dog | f | 1989-05-13 | NULL |

+-------+--------+---------+------+------------+-------+

20.查詢特定的列

查詢表中所有動物的name和birth

mysql> SELECT name, birth FROM pet;

+----------+------------+

| name | birth |

+----------+------------+

| 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 |

+----------+------------+

查詢表中所有的動物

mysql> SELECT owner FROM pet;

+--------+

| owner |

+--------+

| Harold |

| Gwen |

| Harold |

| Benny |

| Diane |

| Gwen |

| Benny |

| Diane |

+--------+

查詢所有名字不相同的動物

mysql> SELECT DISTINCT owner FROM pet;

+--------+

| owner |

+--------+

| Harold |

| Gwen |

| Benny |

| Diane |

+--------+

查詢表中所有dog或者cat的名字，種類，生日

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 |

+--------+---------+------------+

21.排序行

查詢表中所有動物的名字和生日，按生日排序

mysql> SELECT name, birth FROM pet ORDER BY birth;

+----------+------------+

| name | birth |

+----------+------------+

| 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 |

+----------+------------+

查詢表中所有動物的名字和生日，按生日逆序排序

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 |

+----------+------------+

查詢表中所有動物的名字和種類，種類順序，生日逆序

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 |

+----------+---------+------------+

22.日期的計算

計算所有動物的年齡

mysql> SELECT name, birth, CURDATE(),

-> TIMESTAMPDIFF(YEAR,birth,CURDATE()) AS age

-> FROM pet;

+----------+------------+------------+------+

+----------+------------+------------+------+

| Fluffy | 1993-02-04 | 2016-02-23 | 23 |

| Claws | 1994-03-17 | 2016-02-23 | 21 |

| Buffy | 1989-05-13 | 2016-02-23 | 26 |

| Fang | 1990-08-27 | 2016-02-23 | 25 |

| Bowser | 1989-08-31 | 2016-02-23 | 26 |

| Chirpy | 1998-09-11 | 2016-02-23 | 17 |

| Whistler | 1997-12-09 | 2016-02-23 | 18 |

| Slim | 1996-04-29 | 2016-02-23 | 19 |

| Puffball | 1999-03-30 | 2016-02-23 | 16 |

+----------+------------+------------+------+

把剛才查詢出的結果按年齡排序

mysql> SELECT name, birth, CURDATE(),

-> TIMESTAMPDIFF(YEAR,birth,CURDATE()) AS age

-> FROM pet ORDER BY age;

+----------+------------+------------+------+

+----------+------------+------------+------+

| Puffball | 1999-03-30 | 2016-02-23 | 16 |

| Chirpy | 1998-09-11 | 2016-02-23 | 17 |

| Whistler | 1997-12-09 | 2016-02-23 | 18 |

| Slim | 1996-04-29 | 2016-02-23 | 19 |

| Claws | 1994-03-17 | 2016-02-23 | 21 |

| Fluffy | 1993-02-04 | 2016-02-23 | 23 |

| Fang | 1990-08-27 | 2016-02-23 | 25 |

| Buffy | 1989-05-13 | 2016-02-23 | 26 |

| Bowser | 1989-08-31 | 2016-02-23 | 26 |

+----------+------------+------------+------+

計算所有動物的年齡，並且按年齡排序，不包括沒有死亡日期的動物

mysql> SELECT name, birth, death,

-> TIMESTAMPDIFF(YEAR,birth,death) AS age

-> FROM pet WHERE death IS NOT NULL ORDER BY age;

+--------+------------+------------+------+

+--------+------------+------------+------+

| Bowser | 1989-08-31 | 1995-07-29 | 5 |

+--------+------------+------------+------+

查看所有動物的生日是哪個月

YEAR(), MONTH(), and DAYOFMONTH()

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 |

+----------+------------+--------------+

查看所有在5月份過生日的動物的名字和生日

mysql> SELECT name, birth FROM pet WHERE MONTH(birth) = 5;

+-------+------------+

| name | birth |

+-------+------------+

| Buffy | 1989-05-13 |

+-------+------------+

查看下個月過生日的動物

mysql> SELECT name, birth FROM pet

-> WHERE MONTH(birth) = MONTH(DATE_ADD(CURDATE(),INTERVAL 1 MONTH));

+----------+------------+

| name | birth |

+----------+------------+

| Claws | 1994-03-17 |

| Puffball | 1999-03-30 |

+----------+------------+

mysql> SELECT name, birth FROM pet

-> WHERE MONTH(birth) = MOD(MONTH(CURDATE()), 12) + 1;

+----------+------------+

| name | birth |

+----------+------------+

| Claws | 1994-03-17 |

| Puffball | 1999-03-30 |

+----------+------------+

MONTH( ) 返回1到12之間的一個數字；

MOD(something,12 ) 返回0到11之間的一個數字，

所有我們要加數字應該在MOD( )之后。

23.空值的處理

測試查看的值是否為空

mysql> SELECT 1 IS NULL, 1 IS NOT NULL;

+-----------+---------------+

| 1 IS NULL | 1 IS NOT NULL |

+-----------+---------------+

| 0 | 1 |

+-----------+---------------+

你不能用算術運算符操作 NULL , 請看下面的例子：

mysql> SELECT 1 = NULL, 1 <> NULL, 1 < NULL, 1 > NULL;

+----------+-----------+----------+----------+

+----------+-----------+----------+----------+

+----------+-----------+----------+----------+

因為任何的算術運算符把NULL也當做NULL，所以你不能從這些比較重獲取任何有意義的結果。

In MySQL, 0 or NULL means false and anything else means true. The default truth value from a boolean operation is 1.

在MySQL里，0或者NULL就意味着是false , 有時候也是true .默認值 truth是一個boolean類型，值為1.

如果你用 ORDER BY ... ASC 排序，空值會出現在最前面；或 ORDER BY ... DESC 排序，空值會出現在最后面

mysql> SELECT * FROM pet ORDER BY DEATH ASC;

+----------+--------+---------+------+------------+------------+

+----------+--------+---------+------+------------+------------+

| 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 | 1989-08-31 | 1995-07-29 |

+----------+--------+---------+------+------------+------------+

mysql> SELECT * FROM pet ORDER BY DEATH DESC;

+----------+--------+---------+------+------------+------------+

+----------+--------+---------+------+------------+------------+

| Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 |

| 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 |

+----------+--------+---------+------+------------+------------+

當你向表中保存0或者一個空字符串（''）的時候，實際這個列不是空，你可以用 IS [NOT] NULL 測試：

mysql> SELECT 0 IS NULL, 0 IS NOT NULL, '' IS NULL, '' IS NOT NULL;

+-----------+---------------+------------+----------------+

+-----------+---------------+------------+----------------+

| 0 | 1 | 0 | 1 |

+-----------+---------------+------------+----------------+

因此，你可以放入0或一個空字符串到(不能為空 )NOT NULL的列。

24.模式匹配

在MySQL中，SQL的模式匹配默認不區分大小寫。你可以用 “_”匹配任意單個字符，

用“%”匹配匹配任意數量的字符（包括不存在的字符）。

你不能用 = 或者 <>匹配，應該用 LIKE 或 NOT LIKE 代替。

查詢 name字段中以字母 b開頭的動物的信息：

mysql> SELECT * FROM pet WHERE name LIKE 'b%';

+--------+--------+---------+------+------------+------------+

+--------+--------+---------+------+------------+------------+

| Buffy | Harold | dog | f | 1989-05-13 | NULL |

| Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 |

+--------+--------+---------+------+------------+------------+

查詢 name字段中以字母 fy結尾的動物的信息：

mysql> SELECT * FROM pet WHERE name LIKE '%fy';

+--------+--------+---------+------+------------+-------+

+--------+--------+---------+------+------------+-------+

| Fluffy | Harold | cat | f | 1993-02-04 | NULL |

| Buffy | Harold | dog | f | 1989-05-13 | NULL |

+--------+--------+---------+------+------------+-------+

查詢 name字段中包含字母 w 的動物的信息：

mysql> SELECT * FROM pet WHERE name LIKE '%w%';

+----------+-------+---------+------+------------+------------+

+----------+-------+---------+------+------------+------------+

| Claws | Gwen | cat | m | 1994-03-17 | NULL |

| Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 |

+----------+-------+---------+------+------------+------------+

查看名字為五個字符的動物的信息，用“_”字符匹配：

mysql> SELECT * FROM pet WHERE name LIKE '_____';

+-------+--------+---------+------+------------+-------+

+-------+--------+---------+------+------------+-------+

| Claws | Gwen | cat | m | 1994-03-17 | NULL |

| Buffy | Harold | dog | f | 1989-05-13 | NULL |

+-------+--------+---------+------+------------+-------+

MySQL其他類型的匹配，繼承正則表達式：

[ . . . ] 匹配任何在方括號內的字符。比如，[abc]會匹配“a”,"b" 或 "c"。

[a-z] 匹配 a到z中間的任何字母。同樣，[0-9]匹配任何數字。

* 匹配零個或更多的字符。例如，“x*”匹配任何數量的“x”字符。

[0-9]* 匹配任意數量的數字。“.*”匹配任意數量的任何字符。

正則表達式不像模式匹配，正則表達式是匹配任意位置，模式匹配是匹配整個值。

如果一個模式，你必須匹配開始和結尾，

你可以用 “^”作為匹配的開頭，用“$”作為匹配的結尾。

下面將演示如何使用正則表達式進行模式匹配。

找到以“b”開頭的名字，用“^”匹配名字的開頭：

mysql> SELECT * FROM pet WHERE name REGEXP '^b';

+--------+--------+---------+------+------------+------------+

+--------+--------+---------+------+------------+------------+

| Buffy | Harold | dog | f | 1989-05-13 | NULL |

| Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 |

+--------+--------+---------+------+------------+------------+

如果你要強制正則表達式區分大小寫，你可以用 BINARY 關鍵字匹配一個二進制字符串。

此查詢只匹配小寫字母"b"開頭的名稱：

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

Empty set (0.00 sec)

查找以 “ fy”結尾的名字，用“ $”匹配名字的結尾：

mysql> SELECT * FROM pet WHERE name REGEXP 'fy$';

+--------+--------+---------+------+------------+-------+

+--------+--------+---------+------+------------+-------+

| Fluffy | Harold | cat | f | 1993-02-04 | NULL |

| Buffy | Harold | dog | f | 1989-05-13 | NULL |

+--------+--------+---------+------+------------+-------+

查找包含一個“w”的名字

mysql> SELECT * FROM pet WHERE name REGEXP 'w';

+----------+-------+---------+------+------------+------------+

+----------+-------+---------+------+------------+------------+

| Claws | Gwen | cat | m | 1994-03-17 | NULL |

| Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 |

+----------+-------+---------+------+------------+------------+

查找有五個字符組成的名字，用“^”和 “$”匹配開始和結尾，用“.”匹配五個字符：

mysql> SELECT * FROM pet WHERE name REGEXP '^.....$';

+-------+--------+---------+------+------------+-------+

+-------+--------+---------+------+------------+-------+

| Claws | Gwen | cat | m | 1994-03-17 | NULL |

| Buffy | Harold | dog | f | 1989-05-13 | NULL |

+-------+--------+---------+------+------------+-------+

你也可以寫上一個查詢中使用{n}("重復n次")運算符：

mysql> SELECT * FROM pet WHERE name REGEXP '^.{5}$';

+-------+--------+---------+------+------------+-------+

+-------+--------+---------+------+------------+-------+

| Claws | Gwen | cat | m | 1994-03-17 | NULL |

| Buffy | Harold | dog | f | 1989-05-13 | NULL |

+-------+--------+---------+------+------------+-------+

25. 3.3.4.8 計算行

數據庫會經常回答一個問題，“表中的數據多久會發生變化？”、

例如，你可能想知道你有多少只寵物，或者你想知道每個業主有多少只寵物，

或者你想對你的動物進行各類普查。

計算你總共有多少只動物，同樣的問題：pet表中總共有多少行？

因為每個動物有一條記錄。用 COUNG(*)可以計算行數，

所以你可以這樣查詢並計算你的動物：

mysql> SELECT COUNT(*) FROM pet;

+----------+

| COUNT(*) |

+----------+

| 9 |

+----------+

你可以用COUNT()查看每個業主有幾只寵物：

mysql> SELECT owner, COUNT(*) FROM pet GROUP BY owner;

+--------+----------+

| owner | COUNT(*) |

+--------+----------+

| Benny | 2 |

| Diane | 2 |

| Gwen | 3 |

| Harold | 2 |

+--------+----------+

上面的查詢語句用了 GROUP BY 為每位業主分組，

COUNT( ) 和 GROUP BY 一起使用，可以很好的描述你每個組里面的數據。

下面的示例是用另一種方式進行寵物普查。

查看每種動物的數量：

mysql> SELECT species, COUNT(*) FROM pet GROUP BY species;

+---------+----------+

| species | COUNT(*) |

+---------+----------+

| bird | 2 |

| cat | 2 |

| dog | 3 |

| hamster | 1 |

| snake | 1 |

+---------+----------+

查看每種性別的動物的數量：

mysql> SELECT sex, COUNT(*) FROM pet GROUP BY sex;

+------+----------+

| sex | COUNT(*) |

+------+----------+

| NULL | 1 |

| f | 4 |

| m | 4 |

+------+----------+

（在此輸出中，NULL表明，性別是未知的。）

每種組合的動物數量和性別

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 |

+---------+------+----------+

當你使用COUNT( )時，你不用檢索整個表。例如，前面的查詢，

在執行時，只對狗和貓，看起來像這樣：

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 |

+---------+------+----------+

或者，你想知道每個已知性別的動物的數量：

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 |

+---------+------+----------+

如果你選擇了COUNT()列，GROUP BY 子句應存在相同名稱的列。否則，將發生一下錯誤：

如果 ONLY_FULL_GROUP_BY 啟用SQL模式，會發生一個錯誤:

mysql> SET sql_mode = 'ONLY_FULL_GROUP_BY';

Query OK, 0 rows affected, 1 warning (0.22 sec)

mysql> SELECT owner, COUNT(*) FROM pet;

ERROR 1140 (42000): In aggregated query without GROUP BY, expression #1 of SELECT list contains nonaggregated column 'menagerie.pet.owner'; this is incompatible with sql_mode=only_full_group_by

如果 ONLY_FULL_GROUP_BY 沒有啟用，查詢會作為一個單獨的組出來，

但為每個指定的列選定的值是不確定的。MYSQL服務可以自由選擇任何行中的值：

mysql> SET sql_mode = '';

Query OK, 0 rows affected (0.00 sec)

mysql> SELECT owner, COUNT(*) FROM pet;

+--------+----------+

| owner | COUNT(*) |

+--------+----------+

| Harold | 9 |

+--------+----------+

26. 3.3.4.9 使用多個表

pet表會對你所擁有的動物做記錄。如果你想記錄有關他們的其他信息，

像他們的生活中看病和出生，你需要另外一張表。這個表應該是什么樣子？

它需要包含以下信息：

寵物名稱：方便你知道那個動物出了什么情況。

日期（繁殖日期）：方便你知道事情發生的日期。

描述：記錄所發生的事情。

事件類型：如果你要對發生的事情進行分類。

經過上述分析，創建的event table(事件表)可能看起來像這樣：

mysql> CREATE TABLE event (name VARCHAR(20), date DATE,

-> type VARCHAR(15), remark VARCHAR(255));

Query OK, 0 rows affected (1.31 sec)

像pet表一樣，通過創建制表符分割的文本文件，是最容易加載初始信息的方式，文本文件包含以下信息。

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

像下面這樣加載記錄：

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

假設您想查看每個寵物繁殖時的年齡。我們已經看到了兩個日期，但是怎樣從兩個日期中計算某只寵物繁殖時的年齡。

母親的生育日期在event表中，但是要計算他的生育時的年齡，你需要她的生日。她的生日存在pet表中。

這意味着需要查詢兩個表：

mysql> SELECT pet.name,

-> (YEAR(date)-YEAR(birth)) - (RIGHT(date,5)<RIGHT(birth,5)) 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 |

| Buffy | 5 | 3 puppies, 3 female |

+--------+------+-----------------------------+

關於這個查詢有幾件事情需要注意：

From 鏈接了兩個表，因為查詢需要從兩個表中查詢信息。

當結合（加入）多個表的信息時，您需要指定如何將一個表中的記錄與其他中的記錄相匹配。

因為他們都有一個名稱列，這是很容易的。該查詢基於名稱的值，使用ON子句匹配兩個表中的記錄。

該查詢使用 INNER JOIN （內部聯接）把兩個表相結合。 INNER JOIN 內部鏈接是把符合ON條件的兩張表中的信息，

顯示在一張新表中。在這個例子中，ON子句指定名稱的寵物表中的列必須事件表中的列名稱相匹配，

如果一個名稱在兩個表中不是共有的，這個名稱將不顯示，因為ON子句中的條件失敗。

因為 name 列是在兩個表中，你必須明確指出你引用的是哪個表中的哪個列，所有你應該為引用的每個列添加表名。

你不需要有兩個不同的表執行一次聯結。如果你要比較同一個表中的兩條記錄，有時候聯結自己是更實用的。

例如，在你的寵物中找到繁殖的配偶，你可以用pet表聯結他自己，找到雌性和雄性。

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';

+--------+------+--------+------+---------+

+--------+------+--------+------+---------+

| Fluffy | f | Claws | m | cat |

| Buffy | f | Fang | m | dog |

| Buffy | f | Bowser | m | dog |

+--------+------+--------+------+---------+

在這個查詢中，我們指定表的別名名稱引用該表的列和值的實例與每個列引用關聯。

27. 3.4 獲取有關數據庫和表的信息

如果你忘記數據庫或表的名字，或者你忘記了表結構（例如，這個列是存放什么的？）

mysql通過多條語句解決了提供數據庫和表信息的問題。

你以前見到 SHOW DATABASES 命令, 列出由服務器管理的數據庫.

用DATABASE() 命令，你可以找出當前選定的數據庫

mysql> SELECT DATABASE();

+------------+

| DATABASE() |

+------------+

| menagerie |

+------------+

如果你還沒有選中任何的數據庫，這個命令的返回結果是 NULL。

如果你不確定這個數據庫中包含哪些表，你可以用這個語句來查看：

mysql> SHOW TABLES;

+---------------------+

| Tables_in_menagerie |

+---------------------+

| event |

| pet |

+---------------------+

你可以用 DESCRIBE查看表的結構，它描述了每個列的信息。

mysql> DESCRIBE pet;

+---------+-------------+------+-----+---------+-------+

+---------+-------------+------+-----+---------+-------+

| sex | char(1) | YES | | NULL | |

+---------+-------------+------+-----+---------+-------+

Field 表示列的名稱，Type表示列的數據類型，

NULL值指示該列可以包含NULL值，Key指示該列是索引

Default 指出列的默認值，如果列使用了 AUTO_INCREMENT選項，Extra顯示列的額外信息，

這個列的值將會自動增長，而不是空的。

DESC 是 DESCRIBE的縮寫。

mysql> CREATE TABLE pet2(name VARCHAR(20));

Query OK, 0 rows affected (0.36 sec)

mysql> DESCRIBE pet2;

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

mysql> DESC pet2;

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

用SHOW CREATE TABLE 語句，可以顯示你創建表的語句

mysql> SHOW CREATE TABLE pet2;

+-------+-----------------------------------------------------------------------

-----------------------+

| Table | Create Table

+-------+-----------------------------------------------------------------------

-----------------------+

| pet2 | CREATE TABLE `pet2` (

`name` varchar(20) DEFAULT NULL

) ENGINE=InnoDB DEFAULT CHARSET=utf8 |

+-------+-----------------------------------------------------------------------

-----------------------+

28. 3.5 以批處理模式使用mysql

在前面的部分中，您使用mysql交互輸入語句並查看結果。

您還可以使用批處理模式運行mysql。

例如，在d:/mysql_bat/新建login.bat文件，內容如下：

mysql -h localhost -u cunli -pcunli < d:/mysql_bat/mysql.sql > d:/mysql_bat/bat_out.out

然后在d:/mysql_bat/新建mysql.sql ,內容如下：

#show databases;

use menagerie;

#------------tables----------------

show tables;

SELECT * FROM pet;

雙擊login.bat,即可在d:/mysql_bat/看到bat_out.out文件，內容是mysql.sql里面執行的內容

29. 3.6 常見的查詢的例子

啟動命令行，並選中一個數據庫：

你可以使用這些語句創建並填充表：

mysql> use menagerie

Database changed

CREATE TABLE shop (
    article INT(4) UNSIGNED ZEROFILL DEFAULT '0000' NOT NULL,
    dealer  CHAR(20)                 DEFAULT ''     NOT NULL,
    price   DOUBLE(16,2)             DEFAULT '0.00' NOT NULL,
    PRIMARY KEY(article, dealer));
INSERT INTO shop VALUES
    (1,'A',3.45),(1,'B',3.99),(2,'A',10.99),(3,'B',1.45),
    (3,'C',1.69),(3,'D',1.25),(4,'D',19.95);

mysql> CREATE TABLE shop (

-> article INT(4) UNSIGNED ZEROFILL DEFAULT '0000' NOT NULL,

-> dealer CHAR(20) DEFAULT '' NOT NULL,

-> price DOUBLE(16,2) DEFAULT '0.00' NOT NULL,

-> PRIMARY KEY(article, dealer));

Query OK, 0 rows affected (0.28 sec)

mysql> INSERT INTO shop VALUES

-> (1,'A',3.45),(1,'B',3.99),(2,'A',10.99),(3,'B',1.45),

-> (3,'C',1.69),(3,'D',1.25),(4,'D',19.95);

Query OK, 7 rows affected (0.15 sec)

Records: 7 Duplicates: 0 Warnings: 0

查看該表內容：

mysql> SELECT * FROM shop;

+---------+--------+-------+

| article | dealer | price |

+---------+--------+-------+

| 0001 | A | 3.45 |

| 0001 | B | 3.99 |

| 0002 | A | 10.99 |

| 0003 | B | 1.45 |

| 0003 | C | 1.69 |

| 0003 | D | 1.25 |

| 0004 | D | 19.95 |

+---------+--------+-------+

30. 3.6.1 查看列的最大值

該項目的最大編號是多少？

mysql> SELECT MAX(article) AS article FROM shop;

+---------+

| article |

+---------+

| 4 |

+---------+

31. 3.6.2 查看該項目的最大編號的行的信息

mysql> SELECT article, dealer, price

-> FROM shop

-> WHERE price=(SELECT MAX(price) FROM shop);

+---------+--------+-------+

| article | dealer | price |

+---------+--------+-------+

| 0004 | D | 19.95 |

+---------+--------+-------+

你也可以用LIFT JOIN 排序所有的行的價格，然后獲取第一行。或者用LIMT關鍵字：

mysql> SELECT s1.article, s1.dealer, s1.price

-> FROM shop s1

-> LEFT JOIN shop s2 ON s1.price < s2.price

-> WHERE s2.article IS NULL;

+---------+--------+-------+

| article | dealer | price |

+---------+--------+-------+

| 0004 | D | 19.95 |

+---------+--------+-------+

mysql> SELECT article, dealer, price

-> FROM shop

-> ORDER BY price DESC

-> LIMIT 1;

+---------+--------+-------+

| article | dealer | price |

+---------+--------+-------+

| 0004 | D | 19.95 |

+---------+--------+-------+

32. 3.6.3 查看每組中最大的列的值

查看每種物品的最高價格

mysql> SELECT article, MAX(price) AS price

-> FROM shop

-> GROUP BY article;

+---------+-------+

| article | price |

+---------+-------+

| 0001 | 3.99 |

| 0002 | 10.99 |

| 0003 | 1.69 |

| 0004 | 19.95 |

+---------+-------+

33. 3.6.4 查看每種商品的經銷商醉的最高價格

mysql> SELECT article, dealer, price

-> FROM shop s1

-> WHERE price=(SELECT MAX(s2.price)

-> FROM shop s2

-> WHERE s1.article = s2.article);

+---------+--------+-------+

| article | dealer | price |

+---------+--------+-------+

| 0001 | B | 3.99 |

| 0002 | A | 10.99 |

| 0003 | C | 1.69 |

| 0004 | D | 19.95 |

+---------+--------+-------+

無關聯的子查詢：

SELECT s1.article, dealer, s1.price
FROM shop s1
JOIN (
  SELECT article, MAX(price) AS price
  FROM shop
  GROUP BY article) AS s2
  ON s1.article = s2.article AND s1.price = s2.price;

LEFT JOIN:

SELECT s1.article, s1.dealer, s1.price
FROM shop s1
LEFT JOIN shop s2 ON s1.article = s2.article AND s1.price < s2.price
WHERE s2.article IS NULL;

34. 3.6.5 使用用戶定義的變量

你可以使用MySQL用戶變量記住結果，而不必將它們存儲在客戶端中的臨時變量

mysql> SELECT @min_price:=MIN(price),@max_price:=MAX(price) FROM shop;
mysql> SELECT * FROM shop WHERE price=@min_price OR price=@max_price;
+---------+--------+-------+
| article | dealer | price |
+---------+--------+-------+
|    0003 | D      |  1.25 |
|    0004 | D      | 19.95 |
+---------+--------+-------+

mysql> SELECT @min_price:=MIN(price),@max_price:=MAX(price) FROM shop;

+------------------------+------------------------+

| @min_price:=MIN(price) | @max_price:=MAX(price) |

+------------------------+------------------------+

| 1.25 | 19.95 |

+------------------------+------------------------+

1 row in set (0.00 sec)

mysql> SELECT * FROM shop WHERE price=@min_price OR price=@max_price;

+---------+--------+-------+

| article | dealer | price |

+---------+--------+-------+

| 0003 | D | 1.25 |

| 0004 | D | 19.95 |

+---------+--------+-------+

35. 3.6.6 使用外鍵

你可以使用一個列創建一個聯接列，如下所示

CREATE TABLE person (
    id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
    name CHAR(60) NOT NULL,
    PRIMARY KEY (id)
);

CREATE TABLE shirt (
    id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
    style ENUM('t-shirt', 'polo', 'dress') NOT NULL,
    color ENUM('red', 'blue', 'orange', 'white', 'black') NOT NULL,
    owner SMALLINT UNSIGNED NOT NULL REFERENCES person(id),
    PRIMARY KEY (id)
);

INSERT INTO person VALUES (NULL, 'Antonio Paz');

SELECT @last := LAST_INSERT_ID();

INSERT INTO shirt VALUES
(NULL, 'polo', 'blue', @last),
(NULL, 'dress', 'white', @last),
(NULL, 't-shirt', 'blue', @last);

INSERT INTO person VALUES (NULL, 'Lilliana Angelovska');

SELECT @last := LAST_INSERT_ID();

INSERT INTO shirt VALUES
(NULL, 'dress', 'orange', @last),
(NULL, 'polo', 'red', @last),
(NULL, 'dress', 'blue', @last),
(NULL, 't-shirt', 'white', @last);

SELECT * FROM person;
+----+---------------------+
| id | name                |
+----+---------------------+
|  1 | Antonio Paz         |
|  2 | Lilliana Angelovska |
+----+---------------------+

SELECT * FROM shirt;
+----+---------+--------+-------+
| id | style   | color  | owner |
+----+---------+--------+-------+
|  1 | polo    | blue   |     1 |
|  2 | dress   | white  |     1 |
|  3 | t-shirt | blue   |     1 |
|  4 | dress   | orange |     2 |
|  5 | polo    | red    |     2 |
|  6 | dress   | blue   |     2 |
|  7 | t-shirt | white  |     2 |
+----+---------+--------+-------+


SELECT s.* FROM person p INNER JOIN shirt s
   ON s.owner = p.id
 WHERE p.name LIKE 'Lilliana%'
   AND s.color <> 'white';

+----+-------+--------+-------+
| id | style | color  | owner |
+----+-------+--------+-------+
|  4 | dress | orange |     2 |
|  5 | polo  | red    |     2 |
|  6 | dress | blue   |     2 |
+----+-------+--------+-------+

使用這種方式時， REFERENCES 子句不會在 SHOW CREATE TABLE 或者 DESCRIBE 顯示：

SHOW CREATE TABLE shirt\G
*************************** 1. row ***************************
Table: shirt
Create Table: CREATE TABLE `shirt` (
`id` smallint(5) unsigned NOT NULL auto_increment,
`style` enum('t-shirt','polo','dress') NOT NULL,
`color` enum('red','blue','orange','white','black') NOT NULL,
`owner` smallint(5) unsigned NOT NULL,
PRIMARY KEY  (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1

36. 3.6.8 計算每天訪問

下面的示例說明如何使用位元組函數來計算每月用戶訪問Web頁面的數量

CREATE TABLE t1 (year YEAR(4), month INT(2) UNSIGNED ZEROFILL,
             day INT(2) UNSIGNED ZEROFILL);
INSERT INTO t1 VALUES(2000,1,1),(2000,1,20),(2000,1,30),(2000,2,2),
            (2000,2,23),(2000,2,23);

示例表包含年-月-日值代表用戶對頁面的訪問。確定這些訪問發生在每個月多少不同的日子，使用以下查詢：

SELECT year,month,BIT_COUNT(BIT_OR(1<<day)) AS days FROM t1
       GROUP BY year,month;

+------+-------+------+
| year | month | days |
+------+-------+------+
| 2000 |    01 |    3 |
| 2000 |    02 |    2 |
+------+-------+------+

查詢計算/月，每年組合的表中顯示多少不同的日子，自動刪除重復的條目。

37. 3.6.9 使用AUTO_INCREMENT

AUTO_INCREMENT屬性可用於為新行生成一個唯一標識：

CREATE TABLE animals (
     id MEDIUMINT NOT NULL AUTO_INCREMENT,
     name CHAR(30) NOT NULL,
     PRIMARY KEY (id)
);

INSERT INTO animals (name) VALUES
    ('dog'),('cat'),('penguin'),
    ('lax'),('whale'),('ostrich');

SELECT * FROM animals;

+----+---------+
| id | name    |
+----+---------+
|  1 | dog     |
|  2 | cat     |
|  3 | penguin |
|  4 | lax     |
|  5 | whale   |
|  6 | ostrich |
+----+---------+

沒有為AUTO_INCREMENT列指定值，所以使用自動分配的序列號。

您也可以顯式指定列生成序列號0。如果該列被聲明為NOT NULL，也可以指定NULL的列生成序號。當你向一個AUTO_INCREMENT列中插入任何其他值，則列設置為該值和序列重置，以便下自動生成的值如下順序從最大的列值。

您可以檢索最新的自動生成AUTO_INCREMENT值與LAST_INSERT_ID()SQL函數或mysql_insert_id()C API函數。這些功能是連接特定的，所以它們的返回值不受也是執行插入的另一個連接。

使用了AUTO_INCREMENT列，它足夠大，可以容納的最大序列值，您需要的最小整數數據類型。當達到最大值的數據類型的列，接下來生成序列號的嘗試失敗。如果可能，使用無符號屬性以允許更大的范圍。例如，如果您使用TINYINT，最大允許序列號碼是127。為TINYINT簽名，最大值為255。

開始一個AUTO_INCREMENT 1以外的值，設置該值與CREATE TABLE或ALTER TABLE，像這樣：

mysql> ALTER TABLE tbl AUTO_INCREMENT = 100;

引擎優化

CREATE TABLE animals (
    grp ENUM('fish','mammal','bird') NOT NULL,
    id MEDIUMINT NOT NULL AUTO_INCREMENT,
    name CHAR(30) NOT NULL,
    PRIMARY KEY (grp,id)
) ENGINE=MyISAM;

INSERT INTO animals (grp,name) VALUES
    ('mammal','dog'),('mammal','cat'),
    ('bird','penguin'),('fish','lax'),('mammal','whale'),
    ('bird','ostrich');

SELECT * FROM animals ORDER BY grp,id;

+--------+----+---------+
| grp    | id | name    |
+--------+----+---------+
| fish   |  1 | lax     |
| mammal |  1 | dog     |
| mammal |  2 | cat     |
| mammal |  3 | whale   |
| bird   |  1 | penguin |
| bird   |  2 | ostrich |
+--------+----+---------+

免責聲明！

本站轉載的文章為個人學習借鑒使用，本站對版權不負任何法律責任。如果侵犯了您的隱私權益，請聯系本站郵箱yoyou2525@163.com刪除。

猜您在找 MySQL教程 MySQL教程 | 菜鳥教程 mysql以及mysql bench安裝教程 MySQL和MySQL workbench安裝教程 mysql 5.7.33安裝教程 MySQL下載和安裝教程 MySQL下載和安裝教程 mysql安裝教程詳細 Python MySQL 教程 MySQL的安裝教程