PDO::sqliteCreateAggregatePDO::sqliteCreateFunction
(PHP 5 >= 5.1.0, PECL pdo_sqlite >= 1.0.0)
PDO::sqliteCreateFunction — Registers a User Defined Function for use in SQL statements
Descrierea
Această funcţie este EXPERIMENTALĂ. Comportamentul acestei funcţii, denumirea sa şi orice alte aspecte documentate în privinţa acestei funcţii pot să fie modificate fără preaviz într-o versiune viitoare a PHP. Utilizaţi această funcţie la propriul risc.
This method allows you to register a PHP function with SQLite as an UDF (User Defined Function), so that it can be called from within your SQL statements.
The UDF can be used in any SQL statement that can call functions, such as SELECT and UPDATE statements and also in triggers.
Parametri
- function_name
-
The name of the function used in SQL statements.
- callback
-
Callback function to handle the defined SQL function.
Notă: Callback functions should return a type understood by SQLite (i.e. scalar type).
- num_args
-
Hint to the SQLite parser if the callback function accepts a predetermined number of arguments.
Valorile întroarse
Întoarce valoarea TRUE în cazul succesului sau FALSE în cazul eşecului.
Exemple
Example #1 PDO::sqliteCreateFunction() example
<?php
function md5_and_reverse($string)
{
return strrev(md5($string));
}
$db = new PDO('sqlite:sqlitedb');
$db->sqliteCreateFunction('md5rev', 'md5_and_reverse', 1);
$rows = $db->query('SELECT md5rev(filename) FROM files')->fetchAll();
?>
In this example, we have a function that calculates the md5 sum of a string, and then reverses it. When the SQL statement executes, it returns the value of the filename transformed by our function. The data returned in $rows contains the processed result.
The beauty of this technique is that you do not need to process the result using a foreach loop after you have queried for the data.
You can use PDO::sqliteCreateFunction and PDO::sqliteCreateAggregate to override SQLite native SQL functions.
Notă: This method is not available with the SQLite2 driver. Use the old style sqlite API for that instead.
Vedeţi de asemenea
- PDO::sqliteCreateAggregate
- sqlite_create_function() - Registers a "regular" User Defined Function for use in SQL statements
- sqlite_create_aggregate() - Register an aggregating UDF for use in SQL statements
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User Contributed NotesPDO::sqliteCreateFunction