How do I use a comma separated list of values as a filter in T-SQL?

Question

I have a basic SQL query, starting with:

SELECT top 20 application_id, [name], location_id FROM apps

Now, I would like to finish it so that it does this (written in Pseudocode)

if @lid > 0 then
    WHERE location_id IN (@lid)
else
    WHERE location_id is all values in location_id column

---

As requested, here is an example

application_id             name               location_id
----------------------------------------------------------
1                          Joe Blogs          33
2                          Sam Smith          234
3                          Jeremy Carr        33

@locid is the results given by the user, for example '33, 234'

If @lid is empty then I'd like it to output all rows for location_id with name and application_id. Otherwise, I'd like it to output all rows in relation to the provided numbers in @lid (standing for location_id.

So, if @lid is 0:

application_id             name               location_id
----------------------------------------------------------
1                          Joe Blogs          33
2                          Sam Smith          234
3                          Jeremy Carr        33

Otherwise, if @lid contains '33'

application_id             name               location_id
----------------------------------------------------------
1                          Joe Blogs          33
3                          Jeremy Carr        33

Answer 1

Try using Case, which serves the purpose of an IIF or a ternary operator. Please check this link http://msdn.microsoft.com/en-us/library/ms181765.aspx

cheers