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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2023/01/10 22:22:19 UTC

[GitHub] [arrow-datafusion] alamb commented on issue #4854: Can not ORDER BY an aliased group column

alamb commented on issue #4854:
URL: https://github.com/apache/arrow-datafusion/issues/4854#issuecomment-1377972610

   cc @jackwener  who may have some ideas
   
   FWIW the logical order of operations is like this (from https://learnsql.com/blog/sql-order-of-operation)
   
   ![image](https://user-images.githubusercontent.com/490673/211674490-041940f2-05d2-453b-b71f-043ada380190.png)
   
   So as you are describing yes the columns which are available to ORDER are the output of the GROUP BY -- so that means either `GROUP BY` columns or aggregates (or some expression of them)
   
   For example, this is valid:
   
   ```sql
   SELECT a,b, sum(c)
   FROM foo
   GROUP BY a, b
   ORDER BY a + b; -- note it is order by a+b (an expression of the group columns)
   -- also note the ORDER BY can not contain `c`


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