• MySQL表添加自增列


    mysql> create table zc_test2(id int);
    Query OK, 0 rows affected (1.37 sec)
    
    mysql> insert into zc_test2 values (10),(9),(8),(7),(6);
    Query OK, 5 rows affected (0.04 sec)
    Records: 5  Duplicates: 0  Warnings: 0
    
    mysql> select * from zc_test2;
    +------+
    | id   |
    +------+
    |   10 |
    |    9 |
    |    8 |
    |    7 |
    |    6 |
    +------+
    5 rows in set (0.00 sec)
    
    mysql> ALTER TABLE zc_test2 add id2 int;
    Query OK, 0 rows affected (2.84 sec)
    Records: 0  Duplicates: 0  Warnings: 0
    
    mysql> select * from zc_test2;
    +------+------+
    | id   | id2  |
    +------+------+
    |   10 | NULL |
    |    9 | NULL |
    |    8 | NULL |
    |    7 | NULL |
    |    6 | NULL |
    +------+------+
    5 rows in set (0.00 sec)
    
    mysql> alter table zc_test2 change id2 id2 int NOT NULL AUTO_INCREMENT;
    ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key
    
    mysql> alter table zc_test2 change id2 id2 int NOT NULL AUTO_INCREMENT primary key;
    Query OK, 5 rows affected (1.34 sec)
    Records: 5  Duplicates: 0  Warnings: 0
    
    mysql> select * from zc_test2;
    +------+-----+
    | id   | id2 |
    +------+-----+
    |   10 |   1 |
    |    9 |   2 |
    |    8 |   3 |
    |    7 |   4 |
    |    6 |   5 |
    +------+-----+
    5 rows in set (0.00 sec)
  • 相关阅读:
    bat入门--第一个bat文件
    Egret的Shape
    Less Time, More profit 最大权闭合子图(最大流最小割)
    Mayor's posters POJ
    Stars POJ
    Snacks
    有趣的数列 卡特兰数
    Devu and Flowers lucas定理+容斥原理
    整数分解为2的幂 数学
    易碎的鸟蛋 概率DP
  • 原文地址:https://www.cnblogs.com/zc_0101/p/9155631.html
Copyright © 2020-2023  润新知