Named windows with the WINDOW clause

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PostgreSQL (and the SQL standard) support a WINDOW clause at the bottom of the query: SELECT ROW_NUMBER() OVER w, RANK() OVER w FROM t WINDOW w AS (PARTITION BY dept ORDER BY salary). Both functions share the same window spec 'w' without repeating it. This reduces errors when you refine the window - change it in one place and all functions pick up the update. The WINDOW clause is not supported in all databases (MySQL added it in 8.0; SQL Server does not support it as of 2022).