Bruno Wolff III wrote:
> You can use a distinct on with order by clause as a subselect to eliminate
> the records you don't want. Then you can extract col3 from this subselect
> and order by the original sort order (instead of col3 first) to get the
> desired records in the desired order.
>
> It would look something like:
> select col3 from
> (select distinct on (col3) * from tablename order by col1, col2, col3, col4)
> order by col1, col2, col3, col4;
Unfortunately I need to ORDER BY expression, not plain columns.
SELECT DISTINCT ON (col_1) col_1 FROM tab ORDER BY col_2='foo' DESC, col_1='bar' DESC, col_3='blah' DESC;
fails with:
ERROR: SELECT DISTINCT ON expressions must match initial ORDER BY expressions
:(
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