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1 | 1 | <!-- |
2 | | -$PostgreSQL: pgsql/doc/src/sgml/ref/copy.sgml,v 1.88 2009/09/17 21:13:01 momjian Exp $ |
| 2 | +$PostgreSQL: pgsql/doc/src/sgml/ref/copy.sgml,v 1.89 2009/09/17 21:49:15 momjian Exp $ |
3 | 3 | PostgreSQL documentation |
4 | 4 | --> |
5 | 5 |
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@@ -550,10 +550,13 @@ COPY <replaceable class="parameter">count</replaceable> |
550 | 550 | <para> |
551 | 551 | The <literal>CSV</> format has no standard way to distinguish a |
552 | 552 | <literal>NULL</> value from an empty string. |
553 | | - <productname>PostgreSQL</>'s <command>COPY</> handles this using |
554 | | - quoting. A <literal>NULL</> is output as an empty string without |
555 | | - quotes, while an empty string data value is double-quoted |
556 | | - (<literal>""</>). Reading values follows similar rules. You can |
| 553 | + <productname>PostgreSQL</>'s <command>COPY</> handles this by |
| 554 | + quoting. A <literal>NULL</> is output as the <literal>NULL</> |
| 555 | + parameter and is not quoted, while a non-NULL value matching the |
| 556 | + the <literal>NULL</> parameter string is quoted. Therefore, using the default |
| 557 | + settings, a <literal>NULL</> is written as an unquoted empty |
| 558 | + string, while an empty string data value is written with double quotes |
| 559 | + (<literal>""</>). Reading values follows similar rules. You can |
557 | 560 | use <literal>FORCE NOT NULL</> to prevent <literal>NULL</> input |
558 | 561 | comparisons for specific columns. |
559 | 562 | </para> |
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