Home » Mysql » How to Reset an MySQL AutoIncrement using a MAX value from another table?

How to Reset an MySQL AutoIncrement using a MAX value from another table?

Posted by: admin November 17, 2017 Leave a comment

Questions:

I know this won’t work, tried it in various forms and failed all times. What is the simplest way to achieve the following result?

ALTER TABLE XYZ AUTO_INCREMENT = (select max(ID) from ABC);

This is great for automation projects. Thank you!

SELECT @max := (max(ID)+1) from ABC;        -> This works!
select ID from ABC where ID = (@max-1);     -> This works!
ALTER TABLE XYZ AUTO_INCREMENT = (@max+1);  -> This fails :( Why?
Answers:

Use a Prepared Statement:

  SELECT @max := MAX(ID)+ 1 FROM ABC; 

  PREPARE stmt FROM 'ALTER TABLE ABC AUTO_INCREMENT = ?';
  EXECUTE stmt USING @max;

  DEALLOCATE PREPARE stmt;

Questions:
Answers:

Who is having problem with PREPARE stmt FROM ‘ALTER TABLE XYZ AUTO_INCREMENT = ?’ can use

CREATE PROCEDURE reset_xyz_autoincrement
BEGIN
      SELECT @max := MAX(ID)+ 1 FROM ABC; 
      set @alter_statement = concat('ALTER TABLE temp_job_version AUTO_INCREMENT = ', @max);
      PREPARE stmt FROM @alter_statement;
      EXECUTE stmt;
      DEALLOCATE PREPARE stmt;
END

Questions:
Answers:

I’m creating an automated database transformation script for a new version of my application.

In one table, I needed to change the primary auto-increment field to a different field. Since this page came up first many times while I googled a solution for it, here’s a solution that eventually worked for me:

-- Build a new ID field from entry_id, make it primary and fix the auto_increment for it:
ALTER TABLE  `entries` ADD  `id` INT UNSIGNED NOT NULL FIRST;
UPDATE entries SET id = entry_id;
ALTER TABLE  `entries` ADD PRIMARY KEY (  `id` );

-- ...the tricky part of it:
select @ai := (select max(entry_id)+1 from entries);
set @qry = concat('alter table entries auto_increment=',@ai);
prepare stmt from @qry; execute stmt;

-- ...And now it's possible to switch on the auto_increment:
ALTER TABLE  `entries` CHANGE  `id`  `id` INT( 10 ) UNSIGNED NOT NULL AUTO_INCREMENT;

Questions:
Answers:

Reset Auto Increment IDs.

http://community.spiceworks.com/scripts/show/3042-reset-auto-increment-ids

update all auto increment columns in a database to the smallest possible value based on current values in the databases. We needed to do this after cleaning out a database.

Use a Prepared Statement within a Stored Procedure:

drop PROCEDURE if exists reset_autoincrement;
DELIMITER //
CREATE PROCEDURE reset_autoincrement (IN schemaName varchar(255))
 BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE o_name VARCHAR(255);
    DECLARE o_table VARCHAR(255);
    DECLARE cur1 CURSOR FOR SELECT COLUMN_NAME, TABLE_NAME FROM information_schema.`COLUMNS` WHERE extra LIKE '%auto_increment%' and table_schema=schemaName;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
    OPEN cur1;
    read_loop: LOOP
     FETCH cur1 INTO o_name, o_table;

     IF done THEN
       LEAVE read_loop;
     END IF;

  set @qry1 = concat('SELECT MAX(`',o_name,'`) + 1 as autoincrement FROM `',o_table,'` INTO @ai'); 
  PREPARE stmt1 FROM @qry1;
  EXECUTE stmt1;

  IF @ai IS NOT NULL THEN
      SELECT  o_name, o_table;
   select @qry1;
   select @ai;
   set @qry2 = concat('ALTER TABLE `',o_table,'` AUTO_INCREMENT = ', @ai);
   select @qry2;
   PREPARE stmt2 FROM @qry2;
   EXECUTE stmt2;
  END IF;

    END LOOP;

    CLOSE cur1;
 END //
DELIMITER ;


call reset_autoincrement('my_schema_name');

Questions:
Answers:

following the mysql docs, this worked for me in mysql 5.7:

SET @m = (SELECT MAX(id) + 1 FROM ABC); 
SET @s = CONCAT('ALTER TABLE XYZ AUTO_INCREMENT=', @m);
PREPARE stmt1 FROM @s;
EXECUTE stmt1;
DEALLOCATE PREPARE stmt1;

Questions:
Answers:

Ok guys. I have come up with a not so intuitive solution. The best part is that it works!

SELECT @max := max(ID) from ABC;       
ALTER TABLE XYZ AUTO_INCREMENT = 1;
ALTER TABLE XYZ ADD column ID INTEGER primary key auto_increment;
UPDATE XYZ SET ContactID = (ContactID + @max);

Questions:
Answers:

Personally I’d probably use either a shell script or a little C#/C++ application or PHP/Ruby/Perl script to do this in 2 queries:

  • Grab the value you want SELECT MAX(ID) FROM ABC;
  • Alter the table using the value ALTER TABLE XYZ AUTO_INCREMENT = <insert value retrieved from first query here>

Obviously being careful that the new auto increment won’t cause any key clashes with existing data in the XYZ table.

Questions:
Answers:

If you really want to do this in MySQL alone, you can just dump the dynamically built alter command to a file on disk and then execute it.

Like so:

select concat('ALTER TABLE XYZ AUTO_INCREMENT = ',max(ID)+1,';') as alter_stmt
into outfile '/tmp/alter_xyz_auto_increment.sql'
from ABC;

\. /tmp/alter_xyz_auto_increment.sql