Question

i have two tables, program and event. what i am trying to do is get the closest upcoming event for each program. there exists the possibility however, that a program might have no events attached to it or only events that happened in the past, but i still need the program to show up with an empty value for the event dates, not just go away. so i began implementing an outer join based on what i had googled and found outer apply.

the problem appears to be that i have no access to any of the columns in event, geting the error 'Invalid column name 'start_date'.' (this happens with all three columns, not just start date)

so i either need to learn why i can’t access those columns, or figure out a new way to go about writing the query that returns all programs as well as joins the events table for nearest event/leaves values empty if nothing exists

SELECT 
    p.*, 
    e.type,
    e.start_date,
    e.end_date
FROM 
    program p 
    outer apply (
        select top(1) pk_id from events e where fk_program_id = p.pk_id and end_date >= GetDate()
    ) e

Answer 1

You’re not returning any columns except pk_id from events. Add the other columns to your select statement. 🙂

SELECT TOP(1) p.pk_id, 
              TYPE, 
              start_date, 
              end_date 
FROM   events e 
WHERE  fk_program_id = p.pk_id 
       AND end_date >= Getdate()