SQL Server trigger with loop for multiple row insertion

Question

I've created trigger for my database which handles some insertion but when I add multiple values in 1 SQL query it doesn't work:

ALTER TRIGGER [dbo].[ConferenceDayTrigger]
ON [dbo].[Conferences]
AFTER INSERT
AS 
BEGIN
    DECLARE @ID INT
    DECLARE @dayC INT
    DECLARE @counter INT

    SET @counter = 1
    SET @ID = (SELECT  IDConference FROM Inserted)
    SET @dayC = (SELECT   DATEDIFF(DAY, start,finish) FROM Inserted)

    WHILE @counter <= @dayC + 1 
    BEGIN
        EXEC AddConferenceDay @Id, @counter
        SET @counter = @counter +1
    END
END

For single insertion it works ok. But what should I change/add to make it execute for each row of inserted values?

Solution

If you cannot change the stored procedure, then this might be one of the (very few) cases when a cursor comes to the rescue. Double loops, in fact:

ALTER TRIGGER [dbo].[ConferenceDayTrigger]
ON [dbo].[Conferences]
AFTER INSERT
AS 
BEGIN
     DECLARE @ID INT;
     DECLARE @dayC INT;
     DECLARE @counter INT
     SET @counter = 1;

     DECLARE yucky_Cursor CURSOR FOR
        SELECT IDConference, DATEDIFF(DAY, start,finish) FROM Inserted; 
     OPEN yucky_Cursor; /*Open cursor for reading*/


     FETCH NEXT FROM yucky_Cursor INTO @ID, @dayC;
     WHILE @@FETCH_STATUS = 0 
     BEGIN
         WHILE @counter <= @dayC + 1
         BEGIN
             EXEC AddConferenceDay @Id, @counter;
             SET @counter = @counter + 1;
         END;
         FETCH NEXT FROM yucky_Cursor INTO @ID, @dayC;
     END;

    CLOSE yucky_Cursor;
    DEALLOCATE yucky_Cursor;
END;

I suspect there is a way to refactor and get rid of the cursor and use set-based operations.