I have a table called type:
type
-------
type_id integer
tvalue smallint
...
..
..
tvalue was a second key on this table which now turns out to be unnecessary.
Before I can remove it I need to change the columns which reference it. I
wanted to do this with
alter table alter column using
But the using clause I am using does not work. I think I may just be
misunderstanding how this is done, but I could only find a few examples.
Here is an example of what I have tried:
alter table service.service
alter column environment_tvalue type integer
using select type.type.type_id where tvalue = environment_tvalue and
typeset_id = 1;
Does the expression in the using clause have to be a function?
Any advice would be appreciated.
Thanks,
Craig