How can I join on a stored procedure?

Question

I have a stored procedure that takes no parameters, and it returns two fields. The stored procedure sums up all transactions that are applied to a tenant, and it returns the balance and the id of the tenant.

I want to use the record set it returns with a query, and I need to join it's results on the id of the tenant.

This is my current query:

SELECT t.TenantName, t.CarPlateNumber, t.CarColor, t.Sex, t.SSNO, t.Phone, t.Memo,
        u.UnitNumber,
        p.PropertyName
FROM tblTenant t
    LEFT JOIN tblRentalUnit u
    ON t.UnitID = u.ID

    LEFT JOIN tblProperty p
    ON u.PropertyID = p.ID

ORDER BY p.PropertyName, t.CarPlateNumber

The stored procedure is this:

SELECT tenant.ID AS TenantID, SUM(ISNULL(trans.Amount,0)) AS TenantBalance FROM tblTenant tenant
    LEFT JOIN tblTransaction trans
    ON tenant.ID = trans.TenantID
    GROUP BY tenant.ID

I would like to add the balance from the stored procedure to it also.

How can I do this?

Answer 1

Why not just performing the calculation in your SQL?

SELECT 
  t.TenantName
  , t.CarPlateNumber
  , t.CarColor
  , t.Sex
  , t.SSNO
  , t.Phone
  , t.Memo
  , u.UnitNumber
  , p.PropertyName
  , trans.TenantBalance
FROM tblTenant t
     LEFT JOIN tblRentalUnit u ON t.UnitID = u.ID
     LEFT JOIN tblProperty p ON u.PropertyID = p.ID
     INNER JOIN (
       SELECT tenant.ID AS TenantID, SUM(ISNULL(trans.Amount,0)) AS TenantBalance 
       FROM tblTenant tenant
            LEFT JOIN tblTransaction trans ON tenant.ID = trans.TenantID
       GROUP BY tenant.ID
     ) trans ON trans.ID = t.ID
ORDER BY 
  p.PropertyName
  , t.CarPlateNumber

Answer 2

It has already been answered, the best way work-around is to convert the Stored Procedure into an SQL Function or a View.

The short answer, just as mentioned above, is that you cannot directly JOIN a Stored Procedure in SQL, not unless you create another stored procedure or function using the stored procedure's output into a temporary table and JOINing the temporary table, as explained above.

I will answer this by converting your Stored Procedure into an SQL function and show you how to use it inside a query of your choice.

CREATE FUNCTION fnMyFunc()
RETURNS TABLE AS
RETURN 
(
  SELECT tenant.ID AS TenantID, 
       SUM(ISNULL(trans.Amount,0)) AS TenantBalance 
  FROM tblTenant tenant
    LEFT JOIN tblTransaction trans ON tenant.ID = trans.TenantID
  GROUP BY tenant.ID
)

Now to use that function, in your SQL...

SELECT t.TenantName, 
       t.CarPlateNumber, 
       t.CarColor, 
       t.Sex, 
       t.SSNO, 
       t.Phone, 
       t.Memo,
       u.UnitNumber,
       p.PropertyName
FROM tblTenant t
    LEFT JOIN tblRentalUnit u ON t.UnitID = u.ID
    LEFT JOIN tblProperty p ON u.PropertyID = p.ID
    LEFT JOIN dbo.fnMyFunc() AS a
         ON a.TenantID = t.TenantID
ORDER BY p.PropertyName, t.CarPlateNumber

If you wish to pass parameters into your function from within the above SQL, then I recommend you use CROSS APPLY or CROSS OUTER APPLY.

Read up on that here.

Cheers

Answer 3

The short answer is "you can't". What you'll need to do is either use a subquery or you could convert your existing stored procedure in to a table function. Creating it as function would depend on how "reusable" you would need it to be.