SQLite (PDO)
A good example of a user-defined function in SQLite might be a Unicode-aware LOWER() function. SQLite doesn't come with one because it would make the code much larger. Their rationale is that if you need such a function, you're likely to have one in your environment that you can include into SQLite. And here's how it works:
<?php
function SqliteLower($str)
{
return mb_strtolower($str, 'UTF-8');
}
$pdo->sqliteCreateFunction('LOWER', 'SqliteLower', 1);
?>
(Easy integration of user-defined functions from whatever programming language you use SQLite from is one of the things I like most about SQLite...)
PDO->sqliteCreateFunction()
(No version information available, might be only in CVS)
PDO->sqliteCreateFunction() — Registers a User Defined Function for use in SQL statements
Descrição
PDO
Aviso
Esta função é EXPERIMENTAL. O comportamento desta função, seu nome, incluindo toda documentação pode ser modificado sem aviso em futuras versões do PHP. Esta função deve ser usada por sua própria conta e risco.
This method allows you to register a PHP function with SQLite as an UDF (User Defined Function), so that it can be called from within your SQL statements.
The UDF can be used in any SQL statement that can call functions, such as SELECT and UPDATE statements and also in triggers.
Parâmetros
- function_name
-
The name of the function used in SQL statements.
- callback
-
Callback function to handle the defined SQL function.
Nota: Callback functions should return a type understood by SQLite (i.e. scalar type).
- num_args
-
Hint to the SQLite parser if the callback function accepts a predetermined number of arguments.
Valor Retornado
Retorna TRUE em caso de sucesso ou FALSE em falhas.
Exemplos
Exemplo #1 PDO::sqliteCreateFunction() example
<?php
function md5_and_reverse($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.
Dica
You can use PDO->sqliteCreateFunction() and PDO->sqliteCreateAggregate() to override SQLite native SQL functions.
Nota: This method is not available with the SQLite2 driver. Use the old style sqlite API for that instead.
User Contributed Notes
PDO->sqliteCreateFunction()
PDO->sqliteCreateFunction()
nospam dot list at unclassified dot de
13-Nov-2007 10:35
13-Nov-2007 10:35