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1 | | -<!-- $PostgreSQL: pgsql/doc/src/sgml/ddl.sgml,v 1.84 2009/01/07 22:40:49 tgl Exp $ --> |
| 1 | +<!-- $PostgreSQL: pgsql/doc/src/sgml/ddl.sgml,v 1.85 2009/01/08 12:47:58 petere Exp $ --> |
2 | 2 |
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3 | 3 | <chapter id="ddl"> |
4 | 4 | <title>Data Definition</title> |
@@ -2136,6 +2136,23 @@ VALUES ('New York', NULL, NULL, 'NY'); |
2136 | 2136 | permissions on it. |
2137 | 2137 | </para> |
2138 | 2138 |
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| 2139 | + <para> |
| 2140 | + More generally, note that not all SQL commands are able to work on |
| 2141 | + inheritance hierarchies. Commands that are used for data querying, |
| 2142 | + data modification, or schema modification |
| 2143 | + (e.g., <literal>SELECT</literal>, <literal>UPDATE</literal>, <literal>DELETE</literal>, |
| 2144 | + most variants of <literal>ALTER TABLE</literal>, but |
| 2145 | + not <literal>INSERT</literal> and <literal>ALTER TABLE ... |
| 2146 | + RENAME</literal>) typically default to including child tables and |
| 2147 | + support the <literal>ONLY</literal> notation to exclude them. |
| 2148 | + Commands that do database maintenance and tuning |
| 2149 | + (e.g., <literal>REINDEX</literal>, <literal>VACUUM</literal>) |
| 2150 | + typically only work on individual, physical tables and do no |
| 2151 | + support recursing over inheritance hierarchies. The respective |
| 2152 | + behavior of each individual command is documented in the reference |
| 2153 | + part (<xref linkend="sql-commands">). |
| 2154 | + </para> |
| 2155 | + |
2139 | 2156 | <para> |
2140 | 2157 | A serious limitation of the inheritance feature is that indexes (including |
2141 | 2158 | unique constraints) and foreign key constraints only apply to single |
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