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Diffstat (limited to 'doc/src/sgml/ref/create_table.sgml')
| -rw-r--r-- | doc/src/sgml/ref/create_table.sgml | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml index d936de3f238..5a19f94ce91 100644 --- a/doc/src/sgml/ref/create_table.sgml +++ b/doc/src/sgml/ref/create_table.sgml @@ -2005,6 +2005,30 @@ CREATE TABLE cities_partdef </refsect2> <refsect2> + <title>Constraint Naming</title> + + <para> + The SQL standard says that table and domain constraints must have names + that are unique across the schema containing the table or domain. + <productname>PostgreSQL</productname> is laxer: it only requires + constraint names to be unique across the constraints attached to a + particular table or domain. However, this extra freedom does not exist + for index-based constraints (<literal>UNIQUE</literal>, + <literal>PRIMARY KEY</literal>, and <literal>EXCLUDE</literal> + constraints), because the associated index is named the same as the + constraint, and index names must be unique across all relations within + the same schema. + </para> + + <para> + Currently, <productname>PostgreSQL</productname> does not record names + for <literal>NOT NULL</literal> constraints at all, so they are not + subject to the uniqueness restriction. This might change in a future + release. + </para> + </refsect2> + + <refsect2> <title>Inheritance</title> <para> |