Union proposal #128
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Union proposal #128
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tyt2y3
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Sep 10, 2021
callym
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Oct 25, 2021
EntityModel derive-macro
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This PR is to discuss an union implementation.
Unions are supported equally by MySQL, PostgreSQL and SQLite, with the same syntax.
Unions are by default distinct, MySQL has an optional UNION DISTINCT but it has no differences from a simple UNION.
Instead, UNION ALL doesn't filter results.
In this quite simple implementation, I've put the union(s) before the order by statement, because union queries supports ordering of union-ed data.
To obtain a more complex behavior, users can use union-ed queries as sub-queries of a parent query.