Mixing explicit and implicit joins fails with “There is an entry for table … but it cannot be referenced from this part of the query”

Question

SELECT
      i.*, 
      r.name AS roomname, 
      c.name AS cat, 
      p.key AS imgkey, 
      p.extension AS imgext
   FROM 
      items i, 
      rooms r, 
             


        

Answer 1

Move your JOIN statement next to the table you are joining on:

SELECT
      i.*, 
      r.name AS roomname, 
      c.name AS cat, 
      p.key AS imgkey, 
      p.extension AS imgext
   FROM 
      items i
         LEFT JOIN photos p 
            ON p.referencekey = i.key, 
      rooms r, 
      categories c 
   WHERE 
          i.room = r.key 
      AND r.key = 663308 
      AND i.sitekey = 32201 
      AND c.key = i.categorykey

The long explanation:

A JOIN is part of an expression that results in a source table, used in the FROM clause as a from_item. Your FROM clause has 3 from_item source tables:

• items
• rooms
• categories joined to photos

The error is in the ON join_condition of your categories joined to photos from_item. You are referencing a table, items, that does not exist in the from_item. The solution is to move the photos join into the items from_item, so that you have the following from_item source tables:

• items joined to photos
• rooms
• categories

Sadly, I can't find an example in the documentation that makes clear this relationship between a table in the FROM clause and a JOIN. The SELECT Synopsis shows this syntax and is the best source in the documentation to find this distinction. Notice that a JOIN is not a sibling clause to FROM, but actually part of a from_item within the FROM clause. Thus, if your FROM clause consists of a list of tables, each table in that list can have its own joins. Then it becomes more intuitive that each table involved in a join must be included in a single from_item.