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Diffstat (limited to 'doc/src/sgml/array.sgml')
| -rw-r--r-- | doc/src/sgml/array.sgml | 37 |
1 files changed, 18 insertions, 19 deletions
diff --git a/doc/src/sgml/array.sgml b/doc/src/sgml/array.sgml index 6e731e1448e..bfc373ac052 100644 --- a/doc/src/sgml/array.sgml +++ b/doc/src/sgml/array.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/array.sgml,v 1.69 2009/04/27 16:27:35 momjian Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/array.sgml,v 1.70 2009/06/17 21:58:48 tgl Exp $ --> <sect1 id="arrays"> <title>Arrays</title> @@ -60,18 +60,17 @@ CREATE TABLE tictactoe ( </para> <para> - In addition, the current implementation does not enforce the declared + The current implementation does not enforce the declared number of dimensions either. Arrays of a particular element type are all considered to be of the same type, regardless of size or number - of dimensions. So, declaring the number of dimensions or sizes in - <command>CREATE TABLE</command> is simply documentation, it does not + of dimensions. So, declaring the array size or number of dimensions in + <command>CREATE TABLE</command> is simply documentation; it does not affect run-time behavior. </para> <para> An alternative syntax, which conforms to the SQL standard by using - they keyword <literal>ARRAY</>, can - be used for one-dimensional arrays; + the keyword <literal>ARRAY</>, can be used for one-dimensional arrays. <structfield>pay_by_quarter</structfield> could have been defined as: <programlisting> @@ -109,7 +108,7 @@ CREATE TABLE tictactoe ( for the type, as recorded in its <literal>pg_type</literal> entry. Among the standard data types provided in the <productname>PostgreSQL</productname> distribution, all use a comma - (<literal>,</>), except for the type <literal>box</> which uses a semicolon + (<literal>,</>), except for type <type>box</> which uses a semicolon (<literal>;</>). Each <replaceable>val</replaceable> is either a constant of the array element type, or a subarray. An example of an array constant is: @@ -121,7 +120,7 @@ CREATE TABLE tictactoe ( </para> <para> - To set an element of an array to NULL, write <literal>NULL</> + To set an element of an array constant to NULL, write <literal>NULL</> for the element value. (Any upper- or lower-case variant of <literal>NULL</> will do.) If you want an actual string value <quote>NULL</>, you must put double quotes around it. @@ -211,7 +210,7 @@ INSERT INTO sal_emp First, we show how to access a single element of an array. This query retrieves the names of the employees whose pay changed in the second quarter: - + <programlisting> SELECT name FROM sal_emp WHERE pay_by_quarter[1] <> pay_by_quarter[2]; @@ -230,7 +229,7 @@ SELECT name FROM sal_emp WHERE pay_by_quarter[1] <> pay_by_quarter[2]; <para> This query retrieves the third quarter pay of all employees: - + <programlisting> SELECT pay_by_quarter[3] FROM sal_emp; @@ -248,7 +247,7 @@ SELECT pay_by_quarter[3] FROM sal_emp; <literal><replaceable>lower-bound</replaceable>:<replaceable>upper-bound</replaceable></literal> for one or more array dimensions. For example, this query retrieves the first item on Bill's schedule for the first two days of the week: - + <programlisting> SELECT schedule[1:2][1:1] FROM sal_emp WHERE name = 'Bill'; @@ -417,14 +416,14 @@ SELECT ARRAY[5,6] || ARRAY[[1,2],[3,4]]; </para> <para> - The concatenation operator allows a single element to be pushed to the + The concatenation operator allows a single element to be pushed onto the beginning or end of a one-dimensional array. It also accepts two <replaceable>N</>-dimensional arrays, or an <replaceable>N</>-dimensional and an <replaceable>N+1</>-dimensional array. </para> <para> - When a single element is pushed to either the beginning or end of a + When a single element is pushed onto either the beginning or end of a one-dimensional array, the result is an array with the same lower bound subscript as the array operand. For example: <programlisting> @@ -463,7 +462,7 @@ SELECT array_dims(ARRAY[[1,2],[3,4]] || ARRAY[[5,6],[7,8],[9,0]]); </para> <para> - When an <replaceable>N</>-dimensional array is pushed to the beginning + When an <replaceable>N</>-dimensional array is pushed onto the beginning or end of an <replaceable>N+1</>-dimensional array, the result is analogous to the element-array case above. Each <replaceable>N</>-dimensional sub-array is essentially an element of the <replaceable>N+1</>-dimensional @@ -601,9 +600,9 @@ SELECT * FROM around the array value plus delimiter characters between adjacent items. The delimiter character is usually a comma (<literal>,</>) but can be something else: it is determined by the <literal>typdelim</> setting - for the array's element type. (Among the standard data types provided - in the <productname>PostgreSQL</productname> distribution, all - use a comma, except for <literal>box</>, which uses a semicolon (<literal>;</>).) + for the array's element type. Among the standard data types provided + in the <productname>PostgreSQL</productname> distribution, all use a comma, + except for type <type>box</>, which uses a semicolon (<literal>;</>). In a multidimensional array, each dimension (row, plane, cube, etc.) gets its own level of curly braces, and delimiters must be written between adjacent curly-braced entities of the same level. @@ -657,7 +656,7 @@ SELECT f1[1][-2][3] AS e1, f1[1][-1][5] AS e2 As shown previously, when writing an array value you can use double quotes around any individual array element. You <emphasis>must</> do so if the element value would otherwise confuse the array-value parser. - For example, elements containing curly braces, commas (or the matching + For example, elements containing curly braces, commas (or the data type's delimiter character), double quotes, backslashes, or leading or trailing whitespace must be double-quoted. Empty strings and strings matching the word <literal>NULL</> must be quoted, too. To put a double quote or @@ -668,7 +667,7 @@ SELECT f1[1][-2][3] AS e1, f1[1][-1][5] AS e2 </para> <para> - You can use whitespace before a left brace or after a right + You can add whitespace before a left brace or after a right brace. You can also add whitespace before or after any individual item string. In all of these cases the whitespace will be ignored. However, whitespace within double-quoted elements, or surrounded on both sides by |