[PIVOT/UNPIVOT] Optional AS keyword for value aliases

Author: xitep

src/ast/query.rs

@@ -1589,6 +1589,7 @@ pub enum TableFactor {
     ///
     /// [BigQuery](https://cloud.google.com/bigquery/docs/reference/standard-sql/query-syntax#pivot_operator)
     /// [Snowflake](https://docs.snowflake.com/en/sql-reference/constructs/pivot)
+    /// [Oracle](https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/SELECT.html#GUID-CFA006CA-6FF1-4972-821E-6996142A51C6__GUID-68257B27-1C4C-4C47-8140-5C60E0E65D35)
     Pivot {
         /// The input table to pivot.
         table: Box<TableFactor>,
@@ -1610,8 +1611,10 @@ pub enum TableFactor {
     /// table UNPIVOT [ { INCLUDE | EXCLUDE } NULLS ] (value FOR name IN (column1, [ column2, ... ])) [ alias ]
     /// ```
     ///
-    /// See <https://docs.snowflake.com/en/sql-reference/constructs/unpivot>.
-    /// See <https://docs.databricks.com/aws/en/sql/language-manual/sql-ref-syntax-qry-select-unpivot>.
+    /// [Snowflake](https://docs.snowflake.com/en/sql-reference/constructs/unpivot)
+    /// [Databricks](https://docs.databricks.com/aws/en/sql/language-manual/sql-ref-syntax-qry-select-unpivot)
+    /// [BigQuery](https://docs.cloud.google.com/bigquery/docs/reference/standard-sql/query-syntax#unpivot_operator)
+    /// [Oracle](https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/SELECT.html#GUID-CFA006CA-6FF1-4972-821E-6996142A51C6__GUID-9B4E0389-413C-4014-94A1-0A0571BDF7E1)
     Unpivot {
         /// The input table to unpivot.
         table: Box<TableFactor>,

src/parser/mod.rs

@@ -16172,6 +16172,15 @@ impl<'a> Parser<'a> {
         Ok(ExprWithAlias { expr, alias })
     }
 
+    /// Parse an expression followed by an optional alias; Unlike
+    /// [Self::parse_expr_with_alias] the "AS" keyword between the expression
+    /// and the alias is optional.
+    fn parse_expr_with_alias_optional_as_keyword(&mut self) -> Result<ExprWithAlias, ParserError> {
+        let expr = self.parse_expr()?;
+        let alias = self.parse_identifier_optional_alias()?;
+        Ok(ExprWithAlias { expr, alias })
+    }
+
     /// Parse a PIVOT table factor (ClickHouse/Oracle style pivot), returning a TableFactor.
     pub fn parse_pivot_table_factor(
         &mut self,
@@ -16200,7 +16209,9 @@ impl<'a> Parser<'a> {
         } else if self.peek_sub_query() {
             PivotValueSource::Subquery(self.parse_query()?)
         } else {
-            PivotValueSource::List(self.parse_comma_separated(Self::parse_expr_with_alias)?)
+            PivotValueSource::List(
+                self.parse_comma_separated(Self::parse_expr_with_alias_optional_as_keyword)?,
+            )
         };
         self.expect_token(&Token::RParen)?;
 
@@ -16246,7 +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()
+            p.parse_expr_with_alias_optional_as_keyword()
         })?;
         self.expect_token(&Token::RParen)?;
         let alias = self.maybe_parse_table_alias()?;

tests/sqlparser_common.rs

@@ -11357,6 +11357,12 @@ fn parse_pivot_table() {
         verified_stmt(multiple_value_columns_sql).to_string(),
         multiple_value_columns_sql
     );
+
+    // assert optional "AS" keyword for aliases for pivot values
+    one_statement_parses_to(
+        "SELECT * FROM t PIVOT(SUM(1) FOR a.abc IN (1 x, 'two' y, three z))",
+        "SELECT * FROM t PIVOT(SUM(1) FOR a.abc IN (1 AS x, 'two' AS y, three AS z))",
+    );
 }
 
 #[test]
@@ -11572,6 +11578,12 @@ 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]