AUTO_INCREMENT Value Exceeding the Maximum Value of This Field plus 1

If the value of AUTO_INCREMENT is not equal to the maximum value of this field plus 1 in a data table, the possible causes are as follows:

If the increment is not 1, the value of AUTO_INCREMENT is equal to the maximum value of this field plus the increment. For details, see Starting Value and Increment of AUTO_INCREMENT.

mysql> show variables like 'auto_inc%'; 
+--------------------------+-------+ 
| Variable_name            | Value | 
+--------------------------+-------+ 
| auto_increment_increment | 2     | 
| auto_increment_offset    | 1     | 
+--------------------------+-------+ 
mysql> select * from auto_test1; 
+----+ 
| id | 
+----+ 
|  2 | 
|  4 | 
|  6 | 
|  8 | 
+----+ 
mysql> show create table auto_test1; 
+------------+-----------------------------------------+ 
| Table      | Create Table                            | 
+------------+-----------------------------------------+ 
| auto_test1 | CREATE TABLE `auto_test1` (   
`id` int NOT NULL AUTO_INCREMENT,   
PRIMARY KEY (`id`) 
) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8 | 
+------------+-----------------------------------------+

The value of AUTO_INCREMENT was changed.

mysql> select * from animals; 
+----+-----------+ 
| id | name      | 
+----+-----------+ 
|  1 | fish       | 
|  2 | cat       | 
|  3 | penguin   | 
+----+-----------+ 
mysql> show create table animals; 
+---------+-----------------------------------------------------+ 
| Table   | Create Table                                        | 
+---------+-----------------------------------------------------+ 
| animals | CREATE TABLE `animals` (   
`id` mediumint NOT NULL AUTO_INCREMENT,   
`name` char(30) NOT NULL,   
PRIMARY KEY (`id`) 
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8           | 
+---------+-----------------------------------------------------+ 
mysql> alter table animals AUTO_INCREMENT=100; 
Query OK, 0 rows affected (0.04 sec) 
Records: 0  Duplicates: 0  Warnings: 0 
mysql> show create table animals; 
+---------+-----------------------------------------------------+ 
| Table   | Create Table                                        | 
+---------+-----------------------------------------------------+ 
| animals | CREATE TABLE `animals` (   
`id` mediumint NOT NULL AUTO_INCREMENT,   
`name` char(30) NOT NULL,   
PRIMARY KEY (`id`) 
) ENGINE=InnoDB AUTO_INCREMENT=100 DEFAULT CHARSET=utf8         | 
+---------+-----------------------------------------------------+

A transaction was not committed or was rolled back, so the value of AUTO_INCREMENT increased but did not go back down after the transaction was rolled back.

mysql> show create table auto_test1; 
+------------+----------------------------------------+ 
| Table      | Create Table                           | 
+------------+----------------------------------------+ 
| auto_test1 | CREATE TABLE `auto_test1` (   
`id` int NOT NULL AUTO_INCREMENT,   
PRIMARY KEY (`id`) 
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 | 
+------------+----------------------------------------+ 
1 row in set (0.00 sec)  
mysql> select * from auto_test1; 
+----+ 
| id | 
+----+ 
|  1 | 
|  2 | 
|  3 | 
+----+ 
mysql> begin; 
Query OK, 0 rows affected (0.02 sec)  
mysql> insert into auto_test1 values (0),(0),(0); 
Query OK, 3 rows affected (0.00 sec) 
Records: 3  Duplicates: 0  Warnings: 0  
mysql> select * from auto_test1; 
+----+ 
| id | 
+----+ 
|  1 | 
|  2 | 
|  3 | 
|  4 | 
|  5 | 
|  6 | 
+----+ 
6 rows in set (0.00 sec)  
mysql> show create table auto_test1; 
+------------+----------------------------------------+ 
| Table      | Create Table                           | 
+------------+----------------------------------------+ 
| auto_test1 | CREATE TABLE `auto_test1` (   
`id` int NOT NULL AUTO_INCREMENT,   
PRIMARY KEY (`id`) 
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8 | 
+------------+----------------------------------------+ 
1 row in set (0.00 sec)  
mysql> rollback; 
Query OK, 0 rows affected (0.05 sec)  
mysql> select * from auto_test1; 
+----+ 
| id | 
+----+ 
|  1 | 
|  2 | 
|  3 | 
+----+ 
3 rows in set (0.00 sec)  
mysql> show create table auto_test1; 
+------------+----------------------------------------+ 
| Table      | Create Table                           | 
+------------+----------------------------------------+ 
| auto_test1 | CREATE TABLE `auto_test1` (   
`id` int NOT NULL AUTO_INCREMENT,   
PRIMARY KEY (`id`) 
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8 | 
+------------+----------------------------------------+

After data is inserted, the value of AUTO_INCREMENT changed, but when the corresponding data row was deleted, the value of AUTO_INCREMENT did not decrease.

mysql> show create table auto_test1; 
+------------+----------------------------------------+ 
| Table      | Create Table                           | 
+------------+----------------------------------------+ 
| auto_test1 | CREATE TABLE `auto_test1` (   
`id` int NOT NULL AUTO_INCREMENT,   
PRIMARY KEY (`id`) 
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 | 
+------------+----------------------------------------+ 
1 row in set (0.00 sec)  
mysql> select * from auto_test1; 
+----+ 
| id | 
+----+ 
|  1 | 
|  2 | 
|  3 | 
+----+ 
mysql> insert into auto_test1 values (0),(0),(0); 
Query OK, 3 rows affected (0.00 sec) 
Records: 3  Duplicates: 0  Warnings: 0  
mysql> select * from auto_test1; 
+----+ 
| id | 
+----+ 
|  1 | 
|  2 | 
|  3 | 
|  4 | 
|  5 | 
|  6 | 
+----+ 
6 rows in set (0.00 sec)  
mysql> show create table auto_test1; 
+------------+----------------------------------------+ 
| Table      | Create Table                           | 
+------------+----------------------------------------+ 
| auto_test1 | CREATE TABLE `auto_test1` (   
`id` int NOT NULL AUTO_INCREMENT,   
PRIMARY KEY (`id`) 
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8 | 
+------------+----------------------------------------+ 
1 row in set (0.00 sec)  
mysql> delete from auto_test1 where id>3;  
mysql> select * from auto_test1; 
+----+ 
| id | 
+----+ 
|  1 | 
|  2 | 
|  3 | 
+----+ 
3 rows in set (0.00 sec)  mysql> show create table auto_test1; 
+------------+----------------------------------------+ 
| Table      | Create Table                           | 
+------------+----------------------------------------+ 
| auto_test1 | CREATE TABLE `auto_test1` (   
`id` int NOT NULL AUTO_INCREMENT,   
PRIMARY KEY (`id`) 
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8 | 
+------------+----------------------------------------+

Parent topic: Other Issues

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Starting Value and Increment of AUTO_INCREMENT

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Auto-Increment Field Value Jump

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