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Diffstat (limited to 'doc/src/sgml/array.sgml')
| -rw-r--r-- | doc/src/sgml/array.sgml | 63 |
1 files changed, 48 insertions, 15 deletions
diff --git a/doc/src/sgml/array.sgml b/doc/src/sgml/array.sgml index fc87fdf43f0..4392b51f93b 100644 --- a/doc/src/sgml/array.sgml +++ b/doc/src/sgml/array.sgml @@ -1,4 +1,4 @@ -<!-- $Header: /cvsroot/pgsql/doc/src/sgml/array.sgml,v 1.32 2003/11/01 01:56:28 petere Exp $ --> +<!-- $Header: /cvsroot/pgsql/doc/src/sgml/array.sgml,v 1.33 2003/11/04 09:55:38 petere Exp $ --> <sect1 id="arrays"> <title>Arrays</title> @@ -76,13 +76,45 @@ CREATE TABLE tictactoe ( <sect2> <title>Array Value Input</title> - <para> - Now we can show some <command>INSERT</command> statements. To write an array - value as a literal constant, we enclose the element values within curly - braces and separate them by commas. (If you know C, this is not unlike the - C syntax for initializing structures.) We may put double quotes around any - element value, and must do so if it contains commas or curly braces. - (More details appear below.) + <indexterm> + <primary>array</primary> + <secondary>constant</secondary> + </indexterm> + + <para> + To write an array value as a literal constant, enclose the element + values within curly braces and separate them by commas. (If you + know C, this is not unlike the C syntax for initializing + structures.) You may put double quotes around any element value, + and must do so if it contains commas or curly braces. (More + details appear below.) Thus, the general format of an array + constant is the following: +<synopsis> +'{ <replaceable>val1</replaceable> <replaceable>delim</replaceable> <replaceable>val2</replaceable> <replaceable>delim</replaceable> ... }' +</synopsis> + where <replaceable>delim</replaceable> is the delimiter character + for the type, as recorded in its <literal>pg_type</literal> entry. + (For all built-in types, this is the comma character + <quote><literal>,</literal></>.) Each + <replaceable>val</replaceable> is either a constant of the array + element type, or a subarray. An example of an array constant is +<programlisting> +'{{1,2,3},{4,5,6},{7,8,9}}' +</programlisting> + This constant is a two-dimensional, 3-by-3 array consisting of + three subarrays of integers. + </para> + + <para> + (These kinds of array constants are actually only a special case of + the generic type constants discussed in <xref + linkend="sql-syntax-constants-generic">. The constant is initially + treated as a string and passed to the array input conversion + routine. An explicit type specification might be necessary.) + </para> + + <para> + Now we can show some <command>INSERT</command> statements. <programlisting> INSERT INTO sal_emp @@ -95,14 +127,15 @@ INSERT INTO sal_emp '{20000, 25000, 25000, 25000}', '{{"talk", "consult"}, {"meeting"}}'); </programlisting> - </para> + </para> + + <para> + A limitation of the present array implementation is that individual + elements of an array cannot be SQL null values. The entire array + can be set to null, but you can't have an array with some elements + null and some not. + </para> - <para> - A limitation of the present array implementation is that individual - elements of an array cannot be SQL null values. The entire array can be set - to null, but you can't have an array with some elements null and some - not. - </para> <para> This can lead to surprising results. For example, the result of the previous two inserts looks like this: |