-- define the last customer ID handled
DECLARE @LastCustomerID INT
SET @LastCustomerID = 0

-- define the customer ID to be handled now
DECLARE @CustomerIDToHandle INT

-- select the next customer to handle
SELECT TOP 1 @CustomerIDToHandle = CustomerID
FROM Sales.Customer
WHERE CustomerID > @LastCustomerID
ORDER BY CustomerID

-- as long as we have customers......
WHILE @CustomerIDToHandle IS NOT NULL
BEGIN
    -- call your sproc

    -- set the last customer handled to the one we just handled
    SET @LastCustomerID = @CustomerIDToHandle
    SET @CustomerIDToHandle = NULL

    -- select the next customer to handle
    SELECT TOP 1 @CustomerIDToHandle = CustomerID
    FROM Sales.Customer
    WHERE CustomerID > @LastCustomerID
    ORDER BY CustomerID
END

-- define the last customer ID handled
DECLARE @LastCustomerID INT
SET @LastCustomerID = 0
-- define the customer ID to be handled now
DECLARE @CustomerIDToHandle INT
SET @CustomerIDToHandle = 1

-- as long as we have customers......
WHILE @LastCustomerID <> @CustomerIDTOHandle
BEGIN
  SET @LastCustomerId = @CustomerIDToHandle
  -- select the next customer to handle
  SELECT TOP 1 @CustomerIDTOHandle = CustomerID
  FROM Sales.Customer
  WHERE CustomerID > @LastCustomerId
  ORDER BY CustomerID

  IF @CustomerIDTOHandle <> @LastCustoemrID
  BEGIN
      -- call your sproc
  END


END

-- Declare & init (2008 syntax)
DECLARE @CustomerID INT = 0

-- Iterate over all customers
WHILE (1 = 1)
BEGIN

  -- Get next customerId
  SELECT TOP 1 @CustomerID = CustomerID
  FROM Sales.Customer
  WHERE CustomerID > @CustomerId
  ORDER BY CustomerID

  -- Exit loop if no more customers
  IF @@ROWCOUNT = 0 BREAK;

  -- call your sproc
  EXEC dbo.YOURSPROC @CustomerId

END

SELECT CustomerID, CustomerSum.Total

FROM Customers
CROSS APPLY ufn_ComputeCustomerTotal(Customers.CustomerID) AS CustomerSum

CREATE FUNCTION ComputeCustomerTotal
(
    @CustomerID INT
)
RETURNS TABLE
AS
RETURN
(
    SELECT SUM(CustomerOrder.Amount) AS Total FROM CustomerOrder WHERE CustomerID = @CustomerID
)