snowflake - support for select stmt in parentheses

sql/snowflake/SnowflakeParser.g4

@@ -4052,15 +4052,15 @@ switch_section
 
 // select
 query_statement
-    : with_expression? select_statement set_operators*
+    : with_expression? select_statement_in_parentheses set_operators*
     ;
 
 with_expression
     : WITH common_table_expression (COMMA common_table_expression)*
     ;
 
 common_table_expression
-    : id_ ('(' columns = column_list ')')? AS '(' select_statement set_operators* ')'
+    : id_ (LR_BRACKET columns = column_list RR_BRACKET)? AS select_statement_in_parentheses
     ;
 
 select_statement
@@ -4069,8 +4069,14 @@ select_statement
     ;
 
 set_operators
-    : (UNION ALL? | EXCEPT | MINUS_ | INTERSECT) select_statement //EXCEPT and MINUS have same SQL meaning
-    | LR_BRACKET select_statement RR_BRACKET
+    : (UNION ALL? | EXCEPT | MINUS_ | INTERSECT) select_statement_in_parentheses //EXCEPT and MINUS have same SQL meaning
+    | select_statement_in_parentheses
+    ;
+
+select_statement_in_parentheses
+    : LR_BRACKET select_statement_in_parentheses RR_BRACKET
+    | select_statement_in_parentheses set_operators
+    | select_statement
     ;
 
 select_optional_clauses

sql/snowflake/examples/select.sql

@@ -89,3 +89,24 @@ SELECT EXPR, SCALE, ROUNDING_MODE, SEQUENCE FROM t;
 
 select 'a', 'b',;
 with t as (select 'a', 'b',) select * from t;
+
+with a as((
+    ((
+        select 10 as c
+    ))
+    union
+    ((
+        select 11 as d
+    ))
+))
+   , b as (((
+    ((select 2 as e))
+)))
+select *
+from a
+union
+((select 1 as c));
+
+(((select 10 as c)))
+union
+((select 11 as d));