Question : SQL: Calculating the difference between two dates - working out the age of user given DOB

Hello
This question is regarding MS SQL db. I have the following table:

Area     |    Limit (int)
------------------------
Area1   |     18
Area2   |     21
Area3   |     0
Area4   |     18
Area5   |     54

In SQL, how do I work out the difference between two dates?

I am trying to write a stored procedure, where I pass a parameter @DOB, which is the users' date of birth. Then I need to work out how old the user is and compare it to the area which the are trying to access and see if they are old enough to enter. [By returning true or false or some other kind of indicator]

Also, for example, If they are trying to access Area3, since its limit is 0, we assume then by default that Limit is 21.

Any help would be greatly appreciated. Thanks.

Answer : SQL: Calculating the difference between two dates - working out the age of user given DOB

as gbshahaq mentionnes, you say MS SQL, but posted in MySQL zone?

if it is MS SQL Server:
SELECT * FROM areas
WHERE @DOB <= DATEADD(year, - CASE WHEN  limit = 0 THEN 21 ELSE limit END, getdate())