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| -rw-r--r-- | doc/src/sgml/glossary.sgml | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/doc/src/sgml/glossary.sgml b/doc/src/sgml/glossary.sgml index b88cac598e9..8651f0cdb91 100644 --- a/doc/src/sgml/glossary.sgml +++ b/doc/src/sgml/glossary.sgml @@ -1419,11 +1419,15 @@ <glossterm>Relation</glossterm> <glossdef> <para> - The generic term for all objects in a - <glossterm linkend="glossary-database">database</glossterm> - that have a name and a list of - <glossterm linkend="glossary-attribute">attributes</glossterm> - defined in a specific order. + Mathematically, a <firstterm>relation</firstterm> is a set of + <glossterm linkend="glossary-tuple">tuples</glossterm>; + this is the sense meant in the term "relational database". + </para> + + <para> + In <productname>PostgreSQL</productname>, "relation" is commonly used to + mean an <glossterm linkend="glossary-sql-object">SQL object</glossterm> + that has a name and a list of attributes defined in a specific order. <glossterm linkend="glossary-table">Tables</glossterm>, <glossterm linkend="glossary-sequence">sequences</glossterm>, <glossterm linkend="glossary-view">views</glossterm>, @@ -1431,15 +1435,14 @@ <glossterm linkend="glossary-materialized-view">materialized views</glossterm>, composite types, and <glossterm linkend="glossary-index">indexes</glossterm> are all relations. + A relation in this sense is a container or a descriptor for a set of tuples. </para> + <para> - More generically, a relation is a set of tuples; for example, - the result of a query is also a relation. - </para> - <para> - In <productname>PostgreSQL</productname>, - <firstterm>Class</firstterm> is an archaic synonym for - <firstterm>relation</firstterm>. + <firstterm>Class</firstterm> is an alternative but archaic term. + The system catalog + <link linkend="catalog-pg-class"><structname>pg_class</structname></link> + holds an entry for each <productname>PostgreSQL</productname> relation. </para> </glossdef> </glossentry> |