Question

I am a newbie to DB and SQL. I have the following as a starting point:

CREATE DOMAIN student_numbers AS CHAR(4)
CHECK (SUBSTR(VALUE, 1, 1) = 'S'

What I would like to do is instead checking for ‘S’ only, I would like to check for ‘A’ to ‘Z’.

Also what needs to be done in case I want to check for ‘AAAA’ to ‘ZZZZ’? I gather it maybe possible to assume AAA1 to be a valid value within range, which is not the correct behaviour.

Any guidence or further reading resources would be most welcome.

Thanking you.

Answer 1

I think you can use a regular expression in the CREATE DOMAIN statement, so something like:

CREATE DOMAIN student_numbers AS CHAR(4)
CHECK SUBSTR(VALUE, 1, 1) ~ '[A-Z]'

or for the second one:

CREATE DOMAIN student_numbers AS CHAR(4)
CHECK VALUE ~ '^[A-Z]{4}$'