Simon Willison’s Weblog

21st March 2018 - Link Blog

User-defined Order in SQL (via) This is a fun intellectual exercise: how can one efficiently implement a user-defined order in a SQL table? The obvious initial approach is to have an integer position column, but this means every subsequent row must be updated when an item changes position. Joe “begriffs” Nelson explores some clever alternatives, including floating point or decimal positions (allowing new items to be inserted at a midpoint between existing positions) and a new custom rational number type he buiIt as a PostgreSQL extension.