intersect requires distinct

Author: simonvandel

src/parser/mod.rs

@@ -11171,8 +11171,16 @@ impl<'a> Parser<'a> {
                     pipe_operators.push(PipeOperator::Union { set_quantifier, queries });
                 }
                 Keyword::INTERSECT => {
-                    // Reuse existing set quantifier parser for consistent modifier support
-                    let set_quantifier = self.parse_set_quantifier(&Some(SetOperator::Intersect));
+                    // BigQuery INTERSECT pipe operator requires DISTINCT modifier
+                    let set_quantifier = if self.parse_keywords(&[Keyword::DISTINCT, Keyword::BY, Keyword::NAME]) {
+                        SetQuantifier::DistinctByName
+                    } else if self.parse_keyword(Keyword::DISTINCT) {
+                        SetQuantifier::Distinct
+                    } else {
+                        return Err(ParserError::ParserError(
+                            "INTERSECT pipe operator requires DISTINCT modifier".to_string()
+                        ));
+                    };
                     // BigQuery INTERSECT pipe operator requires parentheses around queries
                     // Parse comma-separated list of parenthesized queries
                     let queries = self.parse_comma_separated(|parser| {

tests/sqlparser_common.rs

@@ -15219,20 +15219,16 @@ fn parse_pipeline_operator() {
     // union pipe operator with BY NAME and multiple queries
     dialects.verified_stmt("SELECT * FROM users |> UNION BY NAME (SELECT * FROM admins), (SELECT * FROM guests)");
 
-    // intersect pipe operator (BigQuery does not support ALL modifier for INTERSECT)
-    dialects.verified_stmt("SELECT * FROM users |> INTERSECT (SELECT * FROM admins)");
+    // intersect pipe operator (BigQuery requires DISTINCT modifier for INTERSECT)
     dialects.verified_stmt("SELECT * FROM users |> INTERSECT DISTINCT (SELECT * FROM admins)");
 
     // intersect pipe operator with BY NAME modifier
-    dialects.verified_stmt("SELECT * FROM users |> INTERSECT BY NAME (SELECT * FROM admins)");
     dialects.verified_stmt("SELECT * FROM users |> INTERSECT DISTINCT BY NAME (SELECT * FROM admins)");
 
     // intersect pipe operator with multiple queries
-    dialects.verified_stmt("SELECT * FROM users |> INTERSECT (SELECT * FROM admins), (SELECT * FROM guests)");
     dialects.verified_stmt("SELECT * FROM users |> INTERSECT DISTINCT (SELECT * FROM admins), (SELECT * FROM guests)");
 
     // intersect pipe operator with BY NAME and multiple queries
-    dialects.verified_stmt("SELECT * FROM users |> INTERSECT BY NAME (SELECT * FROM admins), (SELECT * FROM guests)");
     dialects.verified_stmt("SELECT * FROM users |> INTERSECT DISTINCT BY NAME (SELECT * FROM admins), (SELECT * FROM guests)");
 
     // except pipe operator (BigQuery requires DISTINCT modifier for EXCEPT)
@@ -15280,6 +15276,30 @@ fn parse_pipeline_operator_negative_tests() {
         ParserError::ParserError("EXCEPT pipe operator requires DISTINCT modifier".to_string()),
         dialects.parse_sql_statements("SELECT * FROM users |> EXCEPT ALL BY NAME (SELECT * FROM admins)").unwrap_err()
     );
+
+    // Test that plain INTERSECT without DISTINCT fails
+    assert_eq!(
+        ParserError::ParserError("INTERSECT pipe operator requires DISTINCT modifier".to_string()),
+        dialects.parse_sql_statements("SELECT * FROM users |> INTERSECT (SELECT * FROM admins)").unwrap_err()
+    );
+
+    // Test that INTERSECT ALL fails  
+    assert_eq!(
+        ParserError::ParserError("INTERSECT pipe operator requires DISTINCT modifier".to_string()),
+        dialects.parse_sql_statements("SELECT * FROM users |> INTERSECT ALL (SELECT * FROM admins)").unwrap_err()
+    );
+
+    // Test that INTERSECT BY NAME without DISTINCT fails
+    assert_eq!(
+        ParserError::ParserError("INTERSECT pipe operator requires DISTINCT modifier".to_string()),
+        dialects.parse_sql_statements("SELECT * FROM users |> INTERSECT BY NAME (SELECT * FROM admins)").unwrap_err()
+    );
+
+    // Test that INTERSECT ALL BY NAME fails
+    assert_eq!(
+        ParserError::ParserError("INTERSECT pipe operator requires DISTINCT modifier".to_string()),
+        dialects.parse_sql_statements("SELECT * FROM users |> INTERSECT ALL BY NAME (SELECT * FROM admins)").unwrap_err()
+    );
 }
 
 #[test]