                 _ = try Row.fetchAll(db, request)
                 
                 let selectQueries = sqlQueries.filter { $0.contains("SELECT") }
-                #warning("TODO: remove the harmless but useless LEFT JOIN in the first query")
+                // LEFT JOIN in the first query are useless but harmless.
+                // And SQLite may well optimize them out.
+                // So don't bother removing them.
                 XCTAssertEqual(selectQueries, [
                     """
                     SELECT "a".* \

                _ = try Row.fetchAll(db, request)
                
                let selectQueries = sqlQueries.filter { $0.contains("SELECT") }
                #warning("TODO: remove the harmless but useless LEFT JOIN in the first query")
                XCTAssertEqual(selectQueries, [
                    """
                    SELECT "b".* \

                _ = try Row.fetchAll(db, request)
                
                let selectQueries = sqlQueries.filter { $0.contains("SELECT") }
                // LEFT JOIN in the first query are useless but harmless.
                // And SQLite may well optimize them out.
                // So don't bother removing them.
                XCTAssertEqual(selectQueries, [
                    """
                    SELECT "d".* \
