本节主要内容：
MySQL数据类型之枚举类型ENUM
MySQL数据库提供针对字符串存储的一种特殊数据类型：枚举类型ENUM，这种数据类型可以给予我们更多提高性能、降低存储容量和降低程序代码理解的技巧，前面介绍了首先介绍了四种数据类型的特性总结，其后又分别介绍了布尔类型BOOL或称布尔类型BOOLEAN，以及后续会再单独介绍集合类型SET。
本文详细介绍集合类型enum测试过程与总结，加深对mysql数据库集合类型enum的理解记忆。
n 枚举类型ENUM
a).数据库表mysqlops_enum结构
执行数据库表mysqlops_enum创建的SQL语句：
复制代码代码示例:
root@localhost : test 11:22:29>CREATE TABLE Mysqlops_enum(ID INT NOT NULL AUTO_INCREMENT,
-> Job_typeENUM('DBA','SA','Coding Engineer','JavaScript','NA','QA','','other') NOT NULL,
-> Work_City ENUM('shanghai','beijing','hangzhou','shenzhen','guangzhou','other') NOT NULL DEFAULT 'shanghai',
-> PRIMARY KEY(ID)
-> )ENGINE=InnoDB CHARACTER SET 'utf8' COLLATE 'utf8_general_ci'
Query OK, 0 rows affected (0.00 sec)
执行查询数据库表mysqlops_enum结构的SQL语句：
复制代码代码示例:
root@localhost : test 11:23:31>SHOW CREATE TABLE Mysqlops_enum\G
*************************** 1. row ***************************
Table: Mysqlops_enum
Create Table: CREATE TABLE `Mysqlops_enum` (
`ID` int(11) NOT NULL AUTO_INCREMENT,
`Job_type` enum('DBA','SA','Coding Engineer','JavaScript','NA','QA','','other') NOT NULL,
`Work_City` enum('shanghai','beijing','hangzhou','shenzhen','guangzhou','other') NOT NULL DEFAULT 'shanghai',
PRIMARY KEY (`ID`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
小结：
为方便测试枚举类型，如何处理字段定义的默认值、是否允许为NULL和空值的情况，我们定义了2个枚举类型的字段名，经过对比创建与查询数据库中表的结构信息，没有发现MySQL数据库默认修改任何信息。
b). 写入不同类型的测试数据
写入一条符合枚举类型定义的记录值：
复制代码代码示例:
root@localhost : test 11:22:35>INSERT INTO Mysqlops_enum(ID,Job_type,Work_City) VALUES(1,'QA','shanghai')
Query OK, 1 row affected (0.00 sec)
测试第二个枚举类型字Work_City是否允许为空记录值：
复制代码代码示例:
root@localhost : test 11:22:42>INSERT INTO Mysqlops_enum(ID,Job_type,Work_City) VALUES(2,'NA','')
Query OK, 1 row affected, 1 warning (0.00 sec)
root@localhost : test 11:22:48>SHOW WARNINGS
+---------+------+------------------------------------------------+
| Level | Code | Message |
+---------+------+------------------------------------------------+
| Warning | 1265 | Data truncated for column 'Work_City' at row 1 |
+---------+------+------------------------------------------------+
1 row in set (0.00 sec)
测试第二个枚举类型字段Work_City是否允许存储NULL值：
复制代码代码示例:
root@localhost : test 11:22:53>INSERT INTO Mysqlops_enum(ID,Job_type,Work_City) VALUES(3,'Other',NULL)
ERROR 1048 (23000): Column 'Work_City' cannot be null
测试第一个枚举类型字段Job_type是否可以存储空白值：
复制代码代码示例:
root@localhost : test 11:22:59>INSERT INTO Mysqlops_enum(ID,Job_type,Work_City) VALUES(4,'','hangzhou')
Query OK, 1 row affected (0.00 sec)
测试第二个枚举类型字段Job_City如何处理没有在定义中描述的值域第一个枚举类型字段Work_Type的默认值没指定情况下，会默认填写那个值：
复制代码代码示例:
root@localhost : test 11:23:06>INSERT INTO Mysqlops_enum(ID,Work_City) VALUES(5,'ningbo')
Query OK, 1 row affected, 1 warning (0.00 sec)
root@localhost : test 11:23:13>SHOW WARNINGS
+---------+------+------------------------------------------------+
| Level | Code | Message |
+---------+------+------------------------------------------------+
| Warning | 1265 | Data truncated for column 'Work_City' at row 1 |
+---------+------+------------------------------------------------+
1 row in set (0.00 sec)
测试第二个枚举类型字段未插入数据的情况下，是否能使用上字段定义中指定的默认值：
复制代码代码示例:
root@localhost : test 11:23:17>INSERT INTO Mysqlops_enum(ID,Job_type) VALUES(6,'DBA')
Query OK, 1 row affected (0.00 sec)
0. 目标端必须有同名表，没有则建一个空表；
####################################
1、 源端文件准备
源端：
flush tables t for export
复制
t.ibd, t.cfg到目标端。
###############################
flush tables tt7 for export
cp tt7* ../ops
2、 目标端<存在同样的表则>丢弃原来的数据文件
目标端：
alter table tt7 discard tablespace
3、 目标端加载新的数据文件 t.ibd
alter table tt7 import tablespace
4、源端释放锁
源端：
unlock tables
过程中主要异常处理：
#####################################################
SELECT * FROM ops2.tt7
SELECT * FROM ops.tt7
import tablespace报错：
mysql>alter table tt7 import tablespace
ERROR 1812 (HY000): Tablespace is missing for table ops.tt7.
确认再相应的目录存在两个文件
确认属主和权限
#####################################################
过程
[root@qaserver120 ops]# ll
total 80
drwxr-xr-x 2 root root 36 Dec 2 21:42 000
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt2.ibd
[root@qaserver120 ops]#
[root@qaserver120 ops]#
[root@qaserver120 ops]#
[root@qaserver120 ops]# cp 000
[root@qaserver120 ops]# ll
drwxr-xr-x 2 root root 36 Dec 2 21:42 000
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt2.ibd
-rw-r----- 1 root root 627 Dec 2 21:45 tt7.cfg
-rw-r----- 1 root root 114688 Dec 2 21:45 tt7.ibd
[root@qaserver120 ops]# chown mysql.mysql tt7*
[root@qaserver120 ops]#
[root@qaserver120 ops]# ll
drwxr-xr-x 2 root root 36 Dec 2 21:42 000
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt2.ibd
-rw-r----- 1 mysql mysql 627 Dec 2 21:45 tt7.cfg
-rw-r----- 1 mysql mysql 114688 Dec 2 21:46 tt7.ibd
[root@qaserver120 ops]#
#####################################################
mysql>show tables
+---------------+
| Tables_in_ops |
+---------------+
| tt2 |
| tt7 |
+---------------+
2 rows in set (0.00 sec)
mysql>select * from tt7
ERROR 1814 (HY000): Tablespace has been discarded for table 'tt7'
mysql>alter table tt7 import tablespace
ERROR 1812 (HY000): Tablespace is missing for table ops.tt7.
mysql>
mysql>alter table tt7 import tablespace
Query OK, 0 rows affected (0.08 sec)
mysql>
mysql>select * from tt7
+--------------+------+
| x | y |
+--------------+------+
| BBBBBB | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
+--------------+------+
7 rows in set (0.00 sec)
mysql>
###############################################
################################################
mysql>mysql>show tables
+----------------+
| Tables_in_ops2 |
+----------------+
| tt2 |
| tt3 |
| tt7 |
+----------------+
3 rows in set (0.00 sec)
mysql>
mysql>use ops
Database changed
mysql>show tables
+---------------+
| Tables_in_ops |
+---------------+
| tt2 |
+---------------+
1 row in set (0.00 sec)
mysql>
mysql>use ops2
Database changed
mysql>select * from tt7
+--------+------+
| x | y |
+--------+------+
| BBBBBB | NULL |
+--------+------+
1 row in set (0.00 sec)
mysql>
mysql>
mysql>insert into tt7 select * from tt3
Query OK, 3 rows affected (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql>insert into tt7 select * from tt3
Query OK, 3 rows affected (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql>select * from tt7
+--------------+------+
| x | y |
+--------------+------+
| BBBBBB | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
+--------------+------+
7 rows in set (0.00 sec)
mysql>
mysql>commit
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>exit
Bye
[root@qaserver120 pkg]# cd /data/mysql/ops2
[root@qaserver120 ops2]# ll
total 240
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt2.ibd
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt3.ibd
-rw-r----- 1 mysql mysql 114688 Dec 2 21:36 tt7.ibd
[root@qaserver120 ops2]#
[root@qaserver120 ops2]#
[root@qaserver120 ops2]#
[root@qaserver120 ops2]# mysql -u'root' -p'fgxkB9Zq40^MFQUi$PJ' -A
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with or \g.
Your MySQL connection id is 56
Server version: 8.0.18 MySQL Community Server - GPL
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help' or '\h' for help. Type '\c' to clear the current input statement.
mysql>use ops2
Database changed
mysql>
mysql>flush tables tt7 for export
Query OK, 0 rows affected (0.00 sec)
mysql>show tables
+----------------+
| Tables_in_ops2 |
+----------------+
| tt2 |
| tt3 |
| tt7 |
+----------------+
3 rows in set (0.01 sec)
mysql>exit
Bye
[root@qaserver120 ops2]# ll
total 240
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt2.ibd
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt3.ibd
-rw-r----- 1 mysql mysql 114688 Dec 2 21:36 tt7.ibd
[root@qaserver120 ops2]# ll
total 240
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt2.ibd
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt3.ibd
-rw-r----- 1 mysql mysql 114688 Dec 2 21:36 tt7.ibd
[root@qaserver120 ops2]# pwd
/data/mysql/ops2
[root@qaserver120 ops2]# cd cd /data/mysql
-bash: cd: cd: No such file or directory
[root@qaserver120 ops2]# cd /data/mysql/ops2
[root@qaserver120 ops2]# ll
total 240
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt2.ibd
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt3.ibd
-rw-r----- 1 mysql mysql 114688 Dec 2 21:36 tt7.ibd
[root@qaserver120 ops2]# ll -al
total 244
drwxr-x--- 2 mysql mysql 51 Dec 2 21:38 .
drwxr-xr-x 12 mysql mysql 4096 Dec 2 21:17 ..
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt2.ibd
-rw-r----- 1 mysql mysql 114688 Dec 2 21:17 tt3.ibd
-rw-r----- 1 mysql mysql 114688 Dec 2 21:36 tt7.ibd
[root@qaserver120 ops2]# pwd
/data/mysql/ops2
[root@qaserver120 ops2]# mysql -u'root' -p'fgxkB9Zq40^MFQUi$PJ' -A
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with or \g.
Your MySQL connection id is 57
Server version: 8.0.18 MySQL Community Server - GPL
Copyright (c) 2000, 2019, 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 ops2
Database changed
mysql>show tables
+----------------+
| Tables_in_ops2 |
+----------------+
| tt2 |
| tt3 |
| tt7 |
+----------------+
3 rows in set (0.00 sec)
mysql>select * from tt7
+--------------+------+
| x | y |
+--------------+------+
| BBBBBB | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
+--------------+------+
7 rows in set (0.00 sec)
mysql>flush tables tt7 for export
Query OK, 0 rows affected (0.00 sec)
mysql>use ops
Database changed
mysql>ll
->
ERROR 1064 (42000): You have an error in your SQL syntaxcheck the manual that corresponds to your MySQL server version for the right syntax to use near 'll' at line 1
mysql>show tables
+---------------+
| Tables_in_ops |
+---------------+
| tt2 |
+---------------+
1 row in set (0.00 sec)
mysql>
mysql>
mysql>alter table tt7 import tablespace
ERROR 1100 (HY000): Table 'tt7' was not locked with LOCK TABLES
mysql>
mysql>
mysql>use ops2
Database changed
mysql>show tables
+----------------+
| Tables_in_ops2 |
+----------------+
| tt2 |
| tt3 |
| tt7 |
+----------------+
3 rows in set (0.00 sec)
mysql>select * from tt7
+--------------+------+
| x | y |
+--------------+------+
| BBBBBB | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
+--------------+------+
7 rows in set (0.00 sec)
mysql>unlock tables
Query OK, 0 rows affected (0.00 sec)
mysql>show create table tt7
+-------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tt7 | CREATE TABLE `tt7` (
`x` varchar(200) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_as_cs DEFAULT NULL,
`y` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_as_cs |
+-------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql>use ops
Database changed
mysql>show tables
+---------------+
| Tables_in_ops |
+---------------+
| tt2 |
+---------------+
1 row in set (0.01 sec)
mysql> CREATE TABLE `tt7` (
-> `x` varchar(200) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_as_cs DEFAULT NULL,
-> `y` int(11) DEFAULT NULL
->) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_as_cs
Query OK, 0 rows affected, 1 warning (0.02 sec)
mysql>
mysql>
mysql>show tables
+---------------+
| Tables_in_ops |
+---------------+
| tt2 |
| tt7 |
+---------------+
2 rows in set (0.00 sec)
mysql>select * from tt7
Empty set (0.00 sec)
mysql>
mysql>alter table tt7 discard tablesapce
ERROR 1064 (42000): You have an error in your SQL syntaxcheck the manual that corresponds to your MySQL server version for the right syntax to use near 'tablesapce' at line 1
mysql>alter table tt7 discard tablespace
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql>
mysql>show tables
+---------------+
| Tables_in_ops |
+---------------+
| tt2 |
| tt7 |
+---------------+
2 rows in set (0.00 sec)
mysql>select * from tt7
ERROR 1814 (HY000): Tablespace has been discarded for table 'tt7'
mysql>
mysql>
mysql>
mysql>show tables
+---------------+
| Tables_in_ops |
+---------------+
| tt2 |
| tt7 |
+---------------+
2 rows in set (0.00 sec)
mysql>select * from tt7
ERROR 1814 (HY000): Tablespace has been discarded for table 'tt7'
mysql>
mysql>
mysql>alter table tt7 import tablespace
ERROR 1812 (HY000): Tablespace is missing for table `ops`.`tt7`.
mysql>
mysql>
mysql>
mysql>alter table tt7 import tablespace
Query OK, 0 rows affected (0.08 sec)
mysql>
mysql>
mysql>select * from tt7
+--------------+------+
| x | y |
+--------------+------+
| BBBBBB | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
+--------------+------+
7 rows in set (0.00 sec)
mysql>SELECT * FROM ops2.tt7
+--------------+------+
| x | y |
+--------------+------+
| BBBBBB | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
+--------------+------+
7 rows in set (0.00 sec)
mysql>SELECT * FROM ops.tt7
+--------------+------+
| x | y |
+--------------+------+
| BBBBBB | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
+--------------+------+
7 rows in set (0.00 sec)
mysql>
mysql>
mysql>
mysql>unlock tables
Query OK, 0 rows affected (0.00 sec)
mysql>unlock tables
Query OK, 0 rows affected (0.00 sec)
mysql>use ops
Database changed
mysql>show tables
+---------------+
| Tables_in_ops |
+---------------+
| tt2 |
| tt7 |
+---------------+
2 rows in set (0.00 sec)
mysql>
mysql>
mysql>
mysql>use ops2
Database changed
mysql>
mysql>
mysql>show tables
+----------------+
| Tables_in_ops2 |
+----------------+
| tt2 |
| tt3 |
| tt7 |
+----------------+
3 rows in set (0.01 sec)
mysql>
mysql>select * from tt7
+--------------+------+
| x | y |
+--------------+------+
| BBBBBB | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
+--------------+------+
7 rows in set (0.00 sec)
mysql>
mysql>use ops
Database changed
mysql>
mysql>
mysql>select * from tt7
+--------------+------+
| x | y |
+--------------+------+
| BBBBBB | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
| AAAAAA | NULL |
| BBBBBB | NULL |
| 555555555555 | NULL |
+--------------+------+
7 rows in set (0.00 sec)
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