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> An enum is a relation This is TRUE. Most people ignore the relational model despite being so simple to learn. But one important thing to note, is that simila
by mamcx 8y ago
> An enum is a relation
This is TRUE. Most people ignore the relational model despite being so simple to learn. But one important thing to note, is that similar how you can say "anything is a object" you can say "anything is a relation".
This is valid SQL:
SELECT * FROM (SELECT 1) a
And because "1" is a relation, a enum is.
Normal rdbms fail at operate to inner values (like the array feature on postgresql) and don't allow to put tables into cells. This is valid at the relational level but you need to do hacky stuff for common rdbms.
SELECT Head =(SELECT * FROM INVOICE)
I'm working in a relational language, and this will be valid:
for i in 1 do
and
select value:Some(1).... where value.isSome
- krychu 8y agoEnums are not relations but data types as indicated in the first paragraph here: https://www.postgresql.org/docs/current/static/datatype-enum.html 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?
- mamcx 8y agoThat is true. In postgresql. Not int the relational model.
- dragonwriter 8y agoFinite 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.