#1025 - Error on rename of './database/#sql-2e0f_1254ba7' to './database/table' (errno: 150)

So I am trying to add a primary key to one of the tables in my database. Right now it has a primary key like this:

PRIMARY KEY (user_id, round_number)

Where user_id is a foreign key.

I am trying to change it to this:

PRIMARY KEY (user_id, round_number, created_at)

I am doing this in phpmyadmin by clicking on the primary key icon in the table structure view.

This is the error I get:

#1025 - Error on rename of './database/#sql-2e0f_1254ba7' to './database/table' (errno: 150)

It is a MySQL database with InnoDB table engine.

 Answers

There is probably another table with a foreign key referencing the primary key you are trying to change.

To find out which table caused the error you can run SHOW ENGINE INNODB STATUS and then look at the LATEST FOREIGN KEY ERROR section.

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For those who are getting to this question via google... this error can also happen if you try to rename a field that is acting as a foreign key.

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If you are trying to delete a column which is a FOREIGN KEY, you must find the correct name which is not the column name. Eg: If I am trying to delete the server field in the Alarms table which is a foreign key to the servers table.

1. SHOW CREATE TABLE alarm; Look for the CONSTRAINT `server_id_refs_id_34554433` FORIEGN KEY (`server_id`) REFERENCES `server` (`id`) line.
2. ALTER TABLE `alarm` DROP FOREIGN KEY `server_id_refs_id_34554433`;
3. ALTER TABLE `alarm` DROP `server_id`

This will delete the foreign key server from the Alarms table.

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If you are adding a foreign key and faced this error, it could be the value in the child table is not present in the parent table.

Let's say for the column to which the foreign key has to be added has all values set to 0 and the value is not available in the table you are referencing it.

You can set some value which is present in the parent table and then adding foreign key worked for me.