+ bulk loading performance.
- You use the
- xreflabel="sql-delete-title"> command to remove rows; the syntax is
- very similar to the UPDATE command. For
- instance, to remove all rows from the products table that have a
- price of 10, use
+ You use the
+ command to remove rows; the syntax is very similar to the
+ UPDATE command. For instance, to remove all
+ rows from the products table that have a price of 10, use
DELETE FROM products WHERE price = 10;
allow users to define set-returning functions
that do not have this limitation. Currently, the point at
which data begins being written to disk is controlled by the
- xreflabel="work_mem">
+
configuration variable. Administrators who have sufficient
memory to store larger result sets in memory should consider
increasing this parameter.
PostgreSQL> gives you two function creation
- modifiers to optimize execution: volatility> (whether the
- function always returns the same result when given the same
- arguments) and strictness
(whether the
- function returns null if any argument is null). Consult the
- reference page for details.
+ modifiers to optimize execution: volatility> (whether
+ the function always returns the same result when given the same
+ arguments) and strictness
(whether the function
+ returns null if any argument is null). Consult the
+ linkend="sql-createfunction" endterm="sql-createfunction-title">
+ reference page for details.
-
+
Queries
The process of retrieving or the command to retrieve data from a
database is called a query. In SQL the
- SELECT command is used to specify queries. The
- general syntax of the SELECT command is
+ command is
+ used to specify queries. The general syntax of the
+ SELECT command is
SELECT select_list FROM table_expression sort_specification
SELECT select_list
FROM table_expression
- LIMIT { number | ALL } OFFSET number
+ LIMIT { number | ALL } OFFSET number
null. RETURNS NULL ON NULL INPUT or
STRICT changes the function so that it is not
invoked if any of its arguments are null; instead, a null result
- is assumed automatically. See
- linkend="sql-createfunction"> for more information.
+ is assumed automatically. See linkend="sql-createfunction"
+ endterm="sql-createfunction-title"> for more information.
- Change the volatility of the function to the specified
- setting. See for details.
+ Change the volatility of the function to the specified setting.
+ See
+ endterm="sql-createfunction-title"> for details.
Change whether the function is a security definer or not. The
key word EXTERNAL is ignored for SQL
- conformance. See for more
- information about this capability.
+ conformance. See
+ endterm="sql-createfunction-title"> for more information about
+ this capability.