Does SQL have a function that return "null" for records which dont exist in a FK realation

Does SQL have a function that return "null" for records which don't exist? Per example in a FK relation ship, that not all records in the first table have a "child" in the second table, so it returns null records.

Thank you very much.

when doing select with 'join's over two tables it would return null.

For example, you have customers and customerdetails table

if you do

select *

from customers

left join customerdetails on customers.customerId = customerdetails.customerId

if there is no customer details for a customer the fields corresponding to the customer details table would be null.

Check the different types of joins 'left join', 'inner join', 'outer join', 'cross join'...i think that's all :)

Cheers,

Yani

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Thank you very much indeedYani Dzhurov.