MySQL自增列测试（DB:5.7.27 OS:CentOS7.6）
情景1：创建包含自增列的新表测试
mysql> create table test05 (id int unsigned auto_increment);
ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key
结论：自增列必须为主键
情景2：创建包含自增列的新表，自增值直接从最大开始，添加新值
mysql> create table test06 (id int unsigned primary key auto_increment ) auto_increment=4294967295;
Query OK, 0 rows affected (0.02 sec)
或者
create table test06 (id int unsigned unique auto_increment ) auto_increment=4294967295;
Query OK, 0 rows affected (0.02 sec)
mysql> insert into test06 values();
Query OK, 1 row affected (0.00 sec)
mysql> insert into test06 values();
ERROR 1062 (23000): Duplicate entry ‘4294967295’ for key ‘PRIMARY’
mysql> select * from test06;
±-----------+
| id |
±-----------+
| 4294967295 |
±-----------+
1 row in set (0.00 sec)
mysql>
结论：自增值超过范围后会报主键重复，无法插入数据。
