Question

I have a table that consists of several Id’s like this

SELECT * FROM Objects;

ObjectId
---------
    1
    4
    5

and function that produce another table for each ObjectId, for instance

SELECT * FROM dbo.GetNumbers(1)        SELECT * FROM dbo.GetNumbers(4)       SELECT * FROM dbo.GetNumbers(5) 

NumberId                               NumberId                              NumberId
---------                              ---------                             ---------
    40                                     11                                    12
    45                                     2                                    
                                           18       

How can I get the cartesian product of original table with the tables produced by functions without using cursors?

    SELECT ???

    ObjectId    NumberId
    ---------------------
        1           40
        1           45
        4           11
        4           2
        4           18
        5           12

Answer 1

Don’t you just want to do?

SELECT
              o.ObjectId
            , n.NumberId
   FROM
            Objects o
       CROSS APPLY
            dbo.GetNumbers(o.ObjectId) n

If you want to include Objects that have no GetNumbers results use OUTER APPLY.

A simple way of looking at it is, CROSS APPLY is an INNER JOIN to a TVF, OUTER APPLY is a LEFT OUTER JOIN to a TVF.

You shouldn’t confuse these with CROSS JOIN which has nothing specific to do with functions and is used to provide the Cartesian Product of two sets, which is not what you want here.