Question

I’ve been looking at this far too long and my brain feels like spaghetti noodles. Could someone help me out with a couple of queries?

Tables:

Presentation
------------
id          int 
name        varchar 
fk_template int     (references template.id)

Template
--------
id          int 
name        varchar 

Position
--------
id          int 
zorder      int     (if it is the 1st, 2nd, 3rd position of the given template)
fk_template int     (references Template.id)

Asset
-----
id          int 
name        varchar 
description varchar 

AssetForPresentation
--------------------
fk_asset        int  (references Asset.id)
fk_presentation int  (references Presentation.id)
fk_position     int  (references Position.id)

What I think I need to be asking at this point is basically “give me all of the assets AND their positions for this template.”

You see, when a Presentation is brought it, it has a specific Template. Each Template has designated Positions, and each Position holds an Asset or NULL.

I need to be able to bring in all Assets and their individual positions for a particular Template used by a Presentation. How would I query for something like that?

I hope this makes sense to you.

Answer 1

I think the part you’re having hard time with is two conditions on JOIN to the AssetForPresentation table.

SELECT
  a.id,
  a.name,
  a.description
FROM Presentation AS p
JOIN Template AS t
  ON p.fk_template = t.id
LEFT JOIN Position AS pos
  ON pos.fk_template = t.id
LEFT JOIN AssetForPresentation AS afp
  ON afp.fk_presentation = p.id
  AND afp.fk_position = pos.id
LEFT JOIN Asset AS a
  ON a.id = afp.fk_asset
WHERE p.id = 123
ORDER BY pos.zorder ASC