dongjoon-hyun edited a comment on issue #27233: [SPARK-29701][SQL] Correct 
behaviours of group analytical queries when empty input given
URL: https://github.com/apache/spark/pull/27233#issuecomment-577487224
 
 
   @tgravescs . Yes, it does. However, this is correctly a SQL correctness 
issue.
   
   Technically, `PostgreSQL` is the only one implementing it according to the 
SQL standard. `SQL:1999` defines `()` as the grand total and the query is 
translated into the following roughly.
   
   ```sql
   ... (other clause)
   UNION ALL
   SELECT CAST(NULL AS DTPC1) AS CNPC1, CAST(NULL AS DTPC2) AS CNPC2, ...  # 
`grand total`
   FROM ...
   ```
   
   This test case is used in PostgreSQL from the beginning of its `Support 
GROUPING SETS, CUBE and ROLLUP` commit (May 15, 2015)
   - 
https://github.com/postgres/postgres/commit/f3d3118532175541a9a96ed78881a3b04a057128#diff-3472ecc50256022c66e79b1aad4075d2R78

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