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更改MySQL表的属性，前期没有考虑到性能问题，将存IP段的列设置了varchar类型，由于数据量询量不断增大，使用char类型存储IP地址不仅占用空间而且影响MySQL查询效率，在多表jion时性能差异就更明显了,所以存储ip用int类型，int只占用4个字节，因为省空间，空间就是效率，选用字段的一般原则是能用占用少字节的字段就不用大字段
MySQL支持5个主要几个类型是tinyint,smallint,mediumint,int,bigint
注:一般程序的字符集是gbk或者utf8，使用char类型跟字符集也有关系
gbk:一个字符占2字节
utf8:一个字符占3个字节
查看本次测试环境
1.当前MySQL版本
mysql> select version();
+------------+
| version() |
+------------+
| 5.6.28-log |
+------------+
1 row in set (0.02 sec)
2.查询原表结构
mysql> desc domain;
+-----------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+--------------+------+-----+---------+----------------+
| id | int(10) | NO | PRI | NULL | auto_increment |
| bd_domain | varchar(255) | YES | UNI | NULL | |
| bd_ip | varchar(16) | YES | | NULL | |
+-----------+--------------+------+-----+---------+----------------+
3.创建测试表
mysql> drop table t1;
Query OK, 0 rows affected (0.08 sec)
mysql> create table t1 select * from bd_domain;
Query OK, 9053585 rows affected (3 min 44.47 sec)
Records: 9053585 Duplicates: 0 Warnings: 0
mysql> select bd_domain,bd_ip from t1 limit 6;
+------------------------+-----------+
| bd_domain | bd_ip |
+------------------------+-----------+
| 039b1ee.netsolhost.com | 0.0.0.0 |
| 03a6b7a.netsolhost.com | 0.0.0.0 |
| 03a6f57.netsolhost.com | 0.0.0.0 |
| 03bbec4.netsolhost.com | 0.0.0.0 |
| 0if1nl6.org | 0.0.0.0 |
| 0x.x.gg | 127.0.0.1 |
+------------------------+-----------+
6 rows in set (0.00 sec)
4.查询新表T1结构，bd_ip列为varchar类型
mysql> desc t1;
+-----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+--------------+------+-----+---------+-------+
| id | int(10) | NO | | 0 | |
| bd_domain | varchar(255) | YES | | NULL | |
| bd_ip | varchar(16) | YES | | NULL | |
+-----------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
5.将t1表的列更改为无符号整形
mysql> UPDATE `t1` SET bd_ip = INET_ATON(bd_ip) WHERE INET_ATON(bd_ip) is NOT NULL;
Query OK, 2588296 rows affected (2 min 2.10 sec)
Rows matched: 2588296 Changed: 2588296 Warnings: 0
6.在执行alter的时候发现第1943555行数据有问题，一般来说可能是这列存在其他字符导致无法更改属性
mysql> ALTER TABLE `t1` CHANGE `bd_ip` `bd_ip` INT UNSIGNED NOT NULL;
ERROR 1366 (HY000): Incorrect integer value: 'False' for column 'bd_ip' at row 1943555
7.现在开始查找第1943555这行数据，t1表有900多万行数据，不太可能从图形化客户端直接查找，利用id范围来确定具体行数，在根据条件定位1943555行的数据
mysql> select count(*) from t1;
+----------+
| count(*) |
+----------+
| 9053585 |
+----------+
1 row in set (3.41 sec)
8.根据id范围来定位1943555这行数据，具体id分为可自行增减
mysql> select count(*) from Mdomain where id<28553491;
+----------+
| count(*) |
+----------+
| 1943553 |
+----------+
1 row in set (0.55 sec)
mysql> select count(*) from Mdomain where id<28553498;
+----------+
| count(*) |
+----------+
| 1943555 |
+----------+
1 row in set (0.56 sec)
9.定位之后查询这行数据，bd_ip此列有False值,因此我们在更改bd_ip列属性时会爆出错误
mysql> select bd_domain,bd_ip from t1 where id=28553497;
+--------------------+-------+
| bd_domain | bd_ip |
+--------------------+-------+
| mysmiledoctors.com | False |
+--------------------+-------+
1 row in set (4.23 sec)
10.更新1943555这列数据，将其更新为整形数据
mysql> update t1 set bd_ip='0' where bd_ip='False';
Query OK, 6465286 rows affected (4 min 17.47 sec)
Rows matched: 6465286 Changed: 6465286 Warnings: 0
11.再次更改bd_ip列属性
mysql> ALTER TABLE `t1` CHANGE `bd_ip` `bd_ip` INT UNSIGNED NOT NULL;
Query OK, 9053581 rows affected (4 min 42.02 sec)
Records: 9053581 Duplicates: 0 Warnings: 0
12.查查看t1表结构
mysql>desc t1;
+-----------+------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+------------------+------+-----+---------+-------+
| id | int(10) | NO | | 0 | |
| bd_domain | varchar(255) | YES | | NULL | |
| bd_ip | int(10) unsigned | NO | | NULL | |
|+-----------+------------------+------+-----+---------+-------+