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A comment on Cost of a Join. Parent comment

Re:Cost of a Join by krychu on Wednesday August 15, 2018 @12:43PM (#17767447)
Enums are not relations but data types as indicated in the first paragraph here: https://www.postgresql.org/docs/current/static/datatype-enum..., and by the related command ‘CREATE TYPE ...’.

Relations are commonly used when referring to tables and views.

What do you gain by calling types relations while introducing confusion and diminishing practicality of the relation concept?

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Re:Cost of a Join by dragonwriter on Wednesday August 15, 2018 @03:49PM (#17769117)
Finite data types are, or are isomorphic to, (constant) relations, they aren't relvars like tables/views (relations include both constant relations and relvars.)

> What do you gain by calling types relations

The fact that everything true of other relations is true of finite types.

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Re:Cost of a Join by mamcx on Wednesday August 15, 2018 @03:08PM (#17768798)
That is true. In postgresql.

Not int the relational model.

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