Is it possible to create a CHECK constraint for my use case?

Hi,

Our Production server is running PostgreSQL v8.2.22 on CentOS5.2. We want
to enable a specific CHECK constraint for our application table as explained
below:

There are 2 columns in the table: "managertype" numeric(1) and "managerid"
numeric(10). "managertype" accepts only 2 valid values, either '1' or '2'.

managertype | managerid
---------------------------------
1 | null values NOT allowed
2 | null values allowed
---------------------------------

We want to enable a CHECK constraint based on 2 columns data in the table in
such a way that if "managertype" is 1, then null values are not allowed in
"managerid" column. In other words, I want to create a CHECK constraint
something like this: IF (managertype = 1) THEN managerid IS NOT NULL.

Is it possible to create a CHECK constraint for my use case explained above?

Regards,
Gnanam