Mysql auto-incrementing primary key return to null _ MySQL

Mysql auto-incrementing primary key-return method bitsCN.com

Recently, it has always been a headache to initialize data for the current project, and the auto-increment of database IDs is getting bigger and bigger, so we need to re-start auto-increment from 1: use the following method:
Method 1: if no data is needed, you can directly clear all data and restore the auto-increment field to count from 1.
Truncate table name

Method 2: set the current value of dbcc checkident ('Table _ name', reseed, new_reseed_value) to new_reseed_value. If the row is not inserted into the table after the table is created, new_reseed_value is used as the ID of the first row inserted after dbcc checkident is executed. Otherwise, new_reseed_value + 1 is used for the next inserted row. If the value of new_reseed_value is smaller than the maximum value in the ID column, error 2627 will be generated when the table is referenced later.
Method 2 does not clear existing data, and the operation is flexible. it can not only return the auto-increment value to zero, but also apply to deleting a large number of consecutive rows, resetting the auto-increment value and inserting new data; or starting from a new value, of course, it cannot conflict with an existing one.

$ SQL = "delete from $ table_vote ";
Mysql_query ($ SQL, $ link );
$ SQL = "alter table $ table_vote auto_increment = 1 ";
Mysql_query ($ SQL, $ link );

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