MySQL 学习日记 2011-8-29

前言

NoSQL都出来很久了。。。我最近刚开始重温重学MySQL的确被某同学鄙视了一下= =

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今天又在折腾那user 数据表。。。

最终成果为以下....// 这是所谓的倒叙写法吗？ 看来我小学语文没忘记，可喜可贺的~

mysql> desc user;
+------------+-------------+------+-----+---------+----------------+
| Field      | Type        | Null | Key | Default | Extra          |
+------------+-------------+------+-----+---------+----------------+
| name       | varchar(20) | YES  | UNI | NULL    |                |
| password   | varchar(20) | YES  |     | NULL    |                |
| sex        | varchar(2)  | YES  |     | NULL    |                |
| email      | varchar(20) | YES  | UNI | NULL    |                |
| reg_time   | date        | YES  |     | NULL    |                |
| permission | int(3)      | NO   |     | NULL    |                |
| ID         | int(3)      | NO   | PRI | NULL    | auto_increment |
+------------+-------------+------+-----+---------+----------------+

虽然这个表有点挫，还有sex明显用gender似乎比较好。。//也许自己懒得改？

那就一切从后往前写吧。。最后一步是把ID附上主键、自增属性的

mysql> alter table user add ID int(3) key  auto_increment;
Query OK, 0 rows affected (0.19 sec)
Records: 0  Duplicates: 0  Warnings: 0

之前我试过。。。

mysql> alter table user add IDD int identity(1,1);

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use near 'ident
ity(1,1)' at line 1
mysql> alter table user add ID int identity(1,1);
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use near 'ident
ity(1,1)' at line 1
mysql> alter table user add ID int(3) identity(1,1);
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use near 'ident
ity(1,1)' at line 1
mysql> alter table user add ID int(3) unique not null auto-increment;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use near 'auto-
increment' at line 1
mysql> alter table user add ID int(3)  not null auto-increment;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use near 'auto-
increment' at line 1
mysql> alter table user add ID int(3)  not null auto_increment;
ERROR 1075 (42000): Incorrect table definition; there can be only one auto colum
n and it must be defined as a key
mysql> alter table user add ID int(3)  auto_increment;
ERROR 1075 (42000): Incorrect table definition; there can be only one auto colum
n and it must be defined as a key

实在是蛋疼。。。

直到我无意瞄到一个关键字。。。这个关键字就是 key。。。

ERROR 1075 (42000): Incorrect table definition; there can be only one auto colum
n and it must be defined as a key

于是就出现我上文使用的最后一条代码。。。

mysql> alter table user add ID int(3) key  auto_increment;

因为我翻w3school找如何（往已有字段）增加AUTO_INCREMENT时一直没有找到。。。于是心情烦躁，就不找Key想碰碰运气随便写写。。就成功了。。。

而这个增加，自增属性的语句。。在W3SCHOOL上解决不能厚，查mysql手册时没查到= =（不过事后查到了=- =）

于是投奔googole。。。然后搜到

http://www.cnblogs.com/me-sa/articles/532528.html

里的

自增列不能直接修改，必须将原有ID列删除，然后重新添加一列具有identity属性的ID字段，语句如下

alter table 表名
drop column ID

alter table 表名
add ID int identity(1,1)

才弄得差不多的。。。

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总之就是，要添加，自增，属性，就要先删才能加。。所谓的从无到有咯~？

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以下，附图一张。。mysql手册里的介绍...