Cant drop Primary key

Databases
1

Hello I am trying to drop a Primary key for a table and I am having some real challenges doing it.

Here is how I originally created the table:

/* 
	Add / Edit Comments about a user in the Admin Panel 
*/
CREATE TABLE USER_COMMENTS
(
	USER_ID			INTEGER(11)		UNSIGNED	NOT NULL,
	COMMENTS		TEXT						NOT NULL,
	COMMENT_DATE	DATETIME					NOT NULL,
	LAST_MODIFIED	DATETIME						NULL,

	CONSTRAINT	CONSTRAINT_PK_USER_COMMENTS
		PRIMARY KEY PK_USER_COMMENTS_USER_ID	(USER_ID),

	CONSTRAINT	CONSTRAINT_FK_USER_COMMENTS
		FOREIGN KEY FK_USER_COMMENTS			(USER_ID)
			REFERENCES	USERS					(USER_ID)
				ON 	DELETE	RESTRICT
				ON	UPDATE	CASCADE,
	
	INDEX	INDEX_USER_COMMENTS_COMMENT_DATE	(COMMENT_DATE)
)
	ENGINE = InnoDB
	DEFAULT CHARACTER SET utf8
	DEFAULT COLLATE utf8_general_ci;

Now i am trying to drop the primary key and change the column of the primary key using the following command:

ALTER TABLE USER_COMMENTS
DROP PRIMARY KEY;

And I am given the following error message:

Error on rename of ‘./users/#sql-1896_919’ to ‘./users/USER_COMMENTS’ (errno: 150)

Any help is highly appreciated.

P.S I have attached a text file with the above scripts in case you are interested.

Thank you in advance for your help.

Kind regards,

Mr. Alexander

2

error 150 means that you have a foreign key in another table that relies on the PK you are trying to delete.

bazz

3

Greetings Bazz,

Thank you for your help, you really nailed down the problem and I was able to drop the primary key.

Kind Regards,

Mr. Alexander