Question

The following two queries are returning different results, to my surprise:

SELECT *
  FROM foo
       JOIN bar
         ON bar.id=foo.bar_id

       JOIN baz
         ON baz.id=foo.baz_id

       LEFT JOIN zig
         ON zig.foo_id=foo.id;

and:

SELECT *
  FROM foo
       LEFT JOIN zig
         ON zig.foo_id=foo.id

       JOIN bar
         ON bar.id=foo.bar_id

       JOIN baz
         ON baz.id=foo.baz_id;

I’m imagining that it shouldn’t matter when you LEFT JOIN on zig, since I’m not using zig‘s columns when joining the bar and baz. However, it appears that in the latter, the JOIN-ing of bar and baz swallows up the rows where zig had null values… why is that?

Answer 1

This works fine. I was wrong.