Q002warning

Ambiguous column

A column name matches more than one table in the current scope.

db/queries/example.sql:2:8: warning[Q002]: ambiguous column reference "id"

   |
 2 | SELECT id, title FROM books JOIN authors ON authors.id = books.author_id;
   |        ^^

Printed by sgl from a small PostgreSQL reproduction project.

When it is reported

Two or more tables in the FROM clause have a column with this name, so the analyser cannot tell which one you mean, and your database would refuse the query too.

How to fix it

Qualify the column with its table or alias, such as users.id.

In your terminal

$ sgl explain Q002

Look for AmbiguousColumn in Seagull's source to see where it is reported.