CHECK CONSTRAINT of string to contain only digits. (Oracle SQL)

Question

I have a column, say PROD_NUM that contains a \'number\' that is left padded with zeros. For example 001004569. They are all nine characters long.

I do not use a num

Answer 1

You already received some nice answers on how to continue on your current path. Please allow me to suggest a different path: use a number(9,0) datatype instead.

Reasons:

• You don't need an additional check constraint to confirm it contains a real number.

• You are not fooling the optimizer. For example, how many prod_num's are "BETWEEN '000000009' and '000000010'"? Lots of character strings fit in there. Whereas "prod_num between 9 and 10" obviously selects only two numbers. Cardinalities will be better, leading to better execution plans.

• You are not fooling future colleagues who have to maintain your code. Naming it "prod_num" will have them automatically assume it contains a number.

Your application can use lpad(to_char(prod_num),9,'0'), preferably exposed in a view.

Regards, Rob.

(update by MH) The comment thread has a discussion which nicely illustrates the various things to consider about this approach. If this topic is interesting you should read them.