[UNPIVOT] Revert to mandatory AS keyword for value aliases

Author: xitep

src/parser/mod.rs

@@ -16257,7 +16257,7 @@ impl<'a> Parser<'a> {
         let name = self.parse_identifier()?;
         self.expect_keyword_is(Keyword::IN)?;
         let columns = self.parse_parenthesized_column_list_inner(Mandatory, false, |p| {
-            p.parse_expr_with_alias_optional_as_keyword()
+            p.parse_expr_with_alias()
         })?;
         self.expect_token(&Token::RParen)?;
         let alias = self.maybe_parse_table_alias()?;

tests/sqlparser_common.rs

@@ -11578,12 +11578,6 @@ fn parse_unpivot_table() {
         verified_stmt(sql_unpivot_with_alias_and_multi_value_and_qualifier).to_string(),
         sql_unpivot_with_alias_and_multi_value_and_qualifier
     );
-
-    // optional AS keyword for unpivot value aliases
-    one_statement_parses_to(
-        "SELECT * FROM sales s UNPIVOT(q FOR quarter IN (Q1 Quater1, Q2 Quater2))",
-        "SELECT * FROM sales s UNPIVOT(q FOR quarter IN (Q1 AS Quater1, Q2 AS Quater2))",
-    );
 }
 
 #[test]