EnricoMi commented on code in PR #37407:
URL: https://github.com/apache/spark/pull/37407#discussion_r981242591
##########
sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBaseParser.g4:
##########
@@ -618,6 +618,46 @@ pivotValue
: expression (AS? identifier)?
;
+unpivotClause
+ : UNPIVOT nullOperator=unpivotNullClause? LEFT_PAREN
+ operator=unpivotOperator
+ RIGHT_PAREN (AS? identifier)?
+ ;
+
+unpivotNullClause
+ : (INCLUDE | EXCLUDE) NULLS
+ ;
+
+unpivotOperator
+ : (unpivotSingleValueColumnClause | unpivotMultiValueColumnClause)
+ ;
+
+unpivotSingleValueColumnClause
+ : unpivotValueColumn FOR unpivotNameColumn IN LEFT_PAREN
unpivotColumns+=unpivotColumn (COMMA unpivotColumns+=unpivotColumn)* RIGHT_PAREN
+ ;
+
+unpivotMultiValueColumnClause
+ : LEFT_PAREN unpivotValueColumns+=unpivotValueColumn (COMMA
unpivotValueColumns+=unpivotValueColumn)* RIGHT_PAREN
+ FOR unpivotNameColumn
+ IN LEFT_PAREN unpivotColumnSets+=unpivotColumnSet (COMMA
unpivotColumnSets+=unpivotColumnSet)* RIGHT_PAREN
+ ;
+
+unpivotColumnSet
+ : LEFT_PAREN unpivotColumns+=unpivotColumn (COMMA
unpivotColumns+=unpivotColumn)* RIGHT_PAREN (AS? identifier)?
Review Comment:
Have have to come back to this:
It looks like Oracle and BigQuery allow for these aliases:
```sql
SELECT * FROM table UNPIVOT (
val for var in (col1 AS alias1, col2 AS alias2)
)
```
and
```sql
SELECT * FROM table UNPIVOT (
(val1, val2) for var in ((col1, col2) AS alias1, (col3, col4) AS alias2)
)
```
but still not
```sql
SELECT * FROM table UNPIVOT (
(val1, val2) for var in ((col1 AS aliasA, col2 AS aliasB) AS alias1, (col3
AS aliasC, col4 AS aliasD) AS alias2)
)
```
(which was your original question).
https://docs.oracle.com/cd/B28359_01/server.111/b28286/statements_10002.htm#SQLRF55133
https://blogs.oracle.com/sql/post/how-to-convert-rows-to-columns-and-back-again-with-sql-aka-pivot-and-unpivot
https://hevodata.com/learn/bigquery-columns-to-rows/#u1
I'll add the former alias again.
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