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Diffstat (limited to 'doc/src/sgml/array.sgml')
| -rw-r--r-- | doc/src/sgml/array.sgml | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/doc/src/sgml/array.sgml b/doc/src/sgml/array.sgml index 4385a09cd97..58878451f00 100644 --- a/doc/src/sgml/array.sgml +++ b/doc/src/sgml/array.sgml @@ -277,6 +277,29 @@ SELECT schedule[1:2][2] FROM sal_emp WHERE name = 'Bill'; </para> <para> + It is possible to omit the <replaceable>lower-bound</replaceable> and/or + <replaceable>upper-bound</replaceable> of a slice specifier; the missing + bound is replaced by the lower or upper limit of the array's subscripts. + For example: + +<programlisting> +SELECT schedule[:2][2:] FROM sal_emp WHERE name = 'Bill'; + + schedule +------------------------ + {{lunch},{presentation}} +(1 row) + +SELECT schedule[:][1:1] FROM sal_emp WHERE name = 'Bill'; + + schedule +------------------------ + {{meeting},{training}} +(1 row) +</programlisting> + </para> + + <para> An array subscript expression will return null if either the array itself or any of the subscript expressions are null. Also, null is returned if a subscript is outside the array bounds (this case does not raise an error). @@ -391,6 +414,10 @@ UPDATE sal_emp SET pay_by_quarter[1:2] = '{27000,27000}' WHERE name = 'Carol'; </programlisting> + The slice syntaxes with omitted <replaceable>lower-bound</replaceable> and/or + <replaceable>upper-bound</replaceable> can be used too, but only when + updating an array value that is not NULL or zero-dimensional (otherwise, + there is no existing subscript limit to substitute). </para> <para> |