Mysql error 150 on column rename

Question

I've an old db with columns'charset to latin1

Now i'm trying to change the whole db in utf8, i've made a script to change all the tables in utf8 like this:

ALTER TABLE `mytable` CHARACTER SET utf8;

and all the columns like this:

ALTER TABLE `mytable` CHANGE `mycolumn` `mycolumn` varchar(200) CHARACTER SET utf8;

But on some columns (primary keys and constraints, i guess) i'm getting this error:

Error on rename of './test/#sql-5028_217b96' to './test/mytable' (errno: 150)

Anyone knows how to get around this?

Answer 1

The most likely your mycolumn is a part of a foreign key. If so, you have to remove the constraint, then change type for the both primary/foreign key and then add constraint again.