added tests

Author: xiedeyantu

datafusion/sqllogictest/test_files/joins.slt

@@ -5516,3 +5516,89 @@ DROP TABLE t1;
 
 statement ok
 DROP TABLE t2;
+
+####
+# Ambiguous unqualified column references through a subquery alias wrapping JOINs.
+# When two or more JOIN inputs share a column name the outer query must use
+# the qualified form (alias.column); bare unqualified references must be rejected.
+####
+
+statement ok
+CREATE TABLE t_left(id INT, age INT, name VARCHAR) AS VALUES
+  (1, 10, 'alice'),
+  (2, 20, 'bob'),
+  (3, 30, 'carol');
+
+statement ok
+CREATE TABLE t_right(id INT, age INT, score INT) AS VALUES
+  (1, 10, 100),
+  (2, 20, 200),
+  (4, 40, 400);
+
+statement ok
+CREATE TABLE t_extra(id INT, dept VARCHAR) AS VALUES
+  (1, 'eng'),
+  (2, 'sales'),
+  (5, 'hr');
+
+# 2-way join: qualified references to columns shared by both sides work fine
+query III rowsort
+SELECT sub.id, sub.age, sub.score
+FROM (SELECT t_left.id, t_left.age, t_right.score
+      FROM t_left JOIN t_right ON t_left.id = t_right.id) AS sub;
+----
+1 10 100
+2 20 200
+
+# 2-way join: unqualified "id" is ambiguous (both sides expose it)
+query error DataFusion error: Schema error: Ambiguous reference to unqualified field id
+SELECT sub.id FROM (SELECT * FROM t_left JOIN t_right ON t_left.id = t_right.id) AS sub WHERE id = 1;
+
+# 2-way join: unqualified "age" is ambiguous (both sides expose it)
+query error DataFusion error: Schema error: Ambiguous reference to unqualified field age
+SELECT sub.age FROM (SELECT * FROM t_left JOIN t_right ON t_left.id = t_right.id) AS sub WHERE age > 5;
+
+# 3-way join: qualified references still work when all three tables share "id"
+query IIIT rowsort
+SELECT sub.id, sub.age, sub.score, sub.dept
+FROM (SELECT t_left.id, t_left.age, t_right.score, t_extra.dept
+      FROM t_left
+      JOIN t_right ON t_left.id = t_right.id
+      JOIN t_extra ON t_left.id = t_extra.id) AS sub;
+----
+1 10 100 eng
+2 20 200 sales
+
+# 3-way join: unqualified "id" is ambiguous (present in all three tables)
+query error DataFusion error: Schema error: Ambiguous reference to unqualified field id
+SELECT sub.id FROM (SELECT * FROM t_left
+                    JOIN t_right ON t_left.id = t_right.id
+                    JOIN t_extra ON t_left.id = t_extra.id) AS sub
+WHERE id = 1;
+
+# 3-way join: unqualified "age" is ambiguous (shared by t_left and t_right)
+query error DataFusion error: Schema error: Ambiguous reference to unqualified field age
+SELECT sub.age FROM (SELECT * FROM t_left
+                     JOIN t_right ON t_left.id = t_right.id
+                     JOIN t_extra ON t_left.id = t_extra.id) AS sub
+WHERE age > 5;
+
+# 3-way join: unambiguous columns (unique to one table) need no qualifier
+query IT rowsort
+SELECT sub.score, sub.dept
+FROM (SELECT t_left.id, t_left.age, t_right.score, t_extra.dept
+      FROM t_left
+      JOIN t_right ON t_left.id = t_right.id
+      JOIN t_extra ON t_left.id = t_extra.id) AS sub;
+----
+100 eng
+200 sales
+
+statement ok
+DROP TABLE t_left;
+
+statement ok
+DROP TABLE t_right;
+
+statement ok
+DROP TABLE t_extra;