I got the below information from a website, when I encountered this error. Hope this would be helpful for you.
In every case this is due to something about the relationship that MySQL doesn’t like. Unfortunately it doesn’t specify what the exact issue is. Here is a running list of causes that people have reported for the dreaded* **errno 150. *I’ve tried to put them in order based on the frequency that I hear about a particular cause. You may want to start by running the MySQL command “SHOW ENGINE INNODB STATUS” immediately after receiving the error. This command displays log info and error details. Note: If your script runs fine on one server, but gives an error when you try to run it on a different server, then there is a good chance that #6 is the problem. Different versions of MySQL have different default charset setting. *Known Causes:* 1. The two key fields type and/or size doesn’t match exactly. For example, if one is INT(10) the key field needs to be INT(10) as well and not INT(11) or TINYINT. You may want to confirm the field size using SHOW CREATE TABLE because Query Browser will sometimes visually show just INTEGER for both INT(10) and INT(11). You should also check that one is not SIGNED and the other is UNSIGNED. They both need to be exactly the same. (More about signed vs unsigned here). 2. One of the key field that you are trying to reference does not have an index and/or is not a primary key. If one of the fields in the relationship is not a primary key, you must create an index for that field. 3. The foreign key name is a duplicate of an already existing key. Check that the name of your foreign key is unique within your database. Just add a few random characters to the end of your key name to test for this. 4. One or both of your tables is a MyISAM table. In order to use foreign keys, the tables must both be InnoDB. (Actually, if both tables are MyISAM then you won’t get an error message – it just won’t create the key.) In Query Browser, you can specify the table type. 5. You have specified a cascade ON DELETE SET NULL, but the relevant key field is set to NOT NULL. You can fix this by either changing your cascade or setting the field to allow NULL values. 6. Make sure that the Charset and Collate options are the same both at the table level as well as individual field level for the key columns. 7. You have a default value (ie default=0) on your foreign key column 8. One of the fields in the relationship is part of a combination (composite) key and does not have it’s own individual index. Even though the field has an index as part of the composite key, you must create a separate index for only that key field in order to use it in a constraint. 9. You have a syntax error in your ALTER statement or you have mistyped one of the field names in the relationship 10. The name of your foreign key exceeds the max length of 64 chars. Regards, Jayabharath.J MySQL DBA, Datavail Corp. On Fri, Jun 11, 2010 at 5:35 AM, SHAWN L.GREEN <shawn.l.gr...@oracle.com>wrote: > On 6/10/2010 6:38 PM, Lola Lee Beno wrote: > >> I'm trying to create a database, using code generated by MySQL Workbench >> 5.2.21 RC. I'm running into this strange issue: >> >> ERROR 1005 (HY000): Can't create table 'nxdb.#sql-a6_3b' (errno: 150) >> >> >> Database was created using utf8 as charset, collation utf8_general_ci. >> >> Original code generated by Workbench: >> >> CREATE TABLE IF NOT EXISTS `nxdb`.`User_Role` ( >> `user_id` VARCHAR(35) NOT NULL , >> `role_id` VARCHAR(35) NOT NULL , >> PRIMARY KEY (`user_id`, `role_id`) , >> CONSTRAINT `user_id` >> FOREIGN KEY (`user_id`) >> REFERENCES `nxdb`.`Users` (`user_id`) >> ON DELETE NO ACTION >> ON UPDATE NO ACTION, >> CONSTRAINT `role_id` >> FOREIGN KEY (`role_id`) >> REFERENCES `nxdb`.`NXRoles` (`role_id`) >> ON DELETE CASCADE >> ON UPDATE CASCADE) >> ENGINE = InnoDB; >> >> (Note, tables Users and NXRoles were already created). This query didn't >> work. So, I stripped down to the basics to get the table created: >> >> CREATE TABLE IF NOT EXISTS `nxdb`.`User_Role` ( >> `user_id` VARCHAR(35) NOT NULL , >> `role_id` VARCHAR(35) NOT NULL , >> PRIMARY KEY (`user_id`, `role_id`) ) >> ENGINE = InnoDB; >> >> Then, I tried running this: >> >> ALTER TABLE `User_Role` ADD >> CONSTRAINT `role_id` >> FOREIGN KEY (`role_id`) >> REFERENCES `NXRoles` (`role_id`) >> ON DELETE CASCADE >> ON UPDATE CASCADE; >> >> And got this error message: ERROR 1005 (HY000): Can't create table >> 'nxdb.#sql-a6_3b' (errno: 150) >> >> When I check the structure of User_Role in phpMyAdmin (couldn't see a way >> to do this in Workbench), this is what I'm seeing: >> >> Action Keyname Type Unique Packed Field Cardinality >> Collation Null Comment >> PRIMARY BTREE Yes No user_id 0 A >> role_id 0 A >> >> >> So, is there no need for me to actually add these constraints? >> >> > For more details about the error 150 code, check the SHOW ENGINE INNODB > STATUS report. > > -- > Shawn Green > MySQL Principle Technical Support Engineer > Oracle USA, Inc. > Office: Blountville, TN > > -- > MySQL General Mailing List > For list archives: http://lists.mysql.com/mysql > To unsubscribe: http://lists.mysql.com/mysql?unsub=jbhara...@gmail.com > >
