mysql自增主键在大量删除后如何重新设置避免断层

select * from tt;
+----+
| id |
+----+
|  1 |
|  2 |
|  3 |
|  4 |
|  5 |
|  6 |
|  7 |
|  8 |

|  9 |

delete from tt where id=8;

Query OK, 1 row affected (0.01 sec)

delete from tt where id=9;

Query OK, 1 row affected (0.01 sec)

>insert into tt values(null);

Query OK, 1 row affected (0.01 sec)

select * from tt;

+----+

| id |

+----+

|  1 |

|  2 |

|  3 |

|  4 |

|  5 |

|  6 |

|  7 |

| 10 |

+----+

看到新插入的记录是在10开始的不是在8开始，如果想要在8开始，需要在删除数据后，重置下自动增长的位置

delete from tt where id=10;

Query OK, 1 row affected (0.01 sec)

alter table tt auto_increment=8

    -> ;

Query OK, 0 rows affected (0.01 sec)

Records: 0  Duplicates: 0  Warnings: 0

insert into tt values(null);

Query OK, 1 row affected (0.00 sec)

select * from tt;

+----+

| id |

+----+

|  1 |

|  2 |

|  3 |

|  4 |

|  5 |

|  6 |

|  7 |

|  8 |

+----+

8 rows in set (0.01 sec)

看到在重新设置后，自增主键是在8开始了，这样可以避免出现id断层