On Tuesday, March 22, 2022, Torsten Förtsch <tfoertsch123(at)gmail(dot)com> wrote:
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> Note the use of aliases, w and x. You are using a correlated subquery.
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Yep. There is an FAQ entry if you’d like a bit more exposition.
https://wiki.postgresql.org/wiki/FAQ#Why_doesn.27t_PostgreSQL_report_a_column_not_found_error_when_using_the_wrong_name_in_a_subquery.3F
David J.