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Is there a specific term to describe a relation with a cardinality of one?

I'm thinking particularly of RDBMS "special" one-row tables, for example, DUAL (Oracle), SYSIBM.SYSDUMMY1 (DB2, Derby) and RDB$DATABASE (Interbase, Firebird).

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Interesting question, I've come across these in some vendor databases, usually "settings" tables –  Ben Brocka Dec 13 '11 at 20:43

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up vote 12 down vote accepted

Singleton Table. In relational terms it is a relation with primary key ∅ (the empty set).

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+1 A colleague suggested this moniker, too. (He also suggested "highlander table," which has a certain charm.) –  pilcrow Dec 13 '11 at 20:02

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