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1 | 1 | <!-- |
2 | | -$PostgreSQL: pgsql/doc/src/sgml/ref/create_domain.sgml,v 1.34 2010/04/03 07:22:58 petere Exp $ |
| 2 | +$PostgreSQL: pgsql/doc/src/sgml/ref/create_domain.sgml,v 1.35 2010/05/29 19:06:16 momjian Exp $ |
3 | 3 | PostgreSQL documentation |
4 | 4 | --> |
5 | 5 |
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@@ -121,7 +121,12 @@ CREATE DOMAIN <replaceable class="parameter">name</replaceable> [ AS ] <replacea |
121 | 121 | <term><literal>NOT NULL</></term> |
122 | 122 | <listitem> |
123 | 123 | <para> |
124 | | - Values of this domain are not allowed to be null. |
| 124 | + Values of this domain are normally prevented from being null. |
| 125 | + However, it is still possible for a domain with this constraint |
| 126 | + to take a null value if it is assigned a matching domain type |
| 127 | + that has become null, e.g. via a LEFT OUTER JOIN, or |
| 128 | + <command>INSERT INTO tab (domcol) VALUES ((SELECT domcol FROM |
| 129 | + tab WHERE false))</command>. |
125 | 130 | </para> |
126 | 131 | </listitem> |
127 | 132 | </varlistentry> |
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