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DB_common::getOne()

DB_common::getOne() -- Runs a query and returns the first column of the first row

Synopsis

mixed &getOne (string $query [, mixed $params = array()])

Описание

Runs the query provided and returns the data from the first column of the first row then frees the result set.

Параметр

string $query

the SQL query or the statement to prepare

mixed $params

array, string or numeric data to be added to the prepared statement. Quantity of items passed must match quantity of placeholders in the prepared statement: meaning 1 placeholder for non-array parameters or 1 placeholder per array element.

If supplied, prepare()/ execute() is used.

Возвращаемое значение

mixed - the first column's data, NULL if there is no data, or a DB_Error object on failure

Throws

Таблица 35-1. Возможные значения PEAR_Error

Error codeError messageReasonSolution
DB_ERROR_INVALID invalid SQL statment for preparing is not valid. See the prepare() documentation, if you want to use a SQL statemt using placeholders.
DB_ERROR_MISMATCH mismatch Quantity of parameters didn't match quantity of placeholders in the prepared statment. Check that the number of placeholders in the prepare() statement passed to $query equals the count of entries passed to $params.
DB_ERROR_NODBSELECTED no database selected No database was choosen. Check the DSN in connect().
every other error code  Database specific error Check the database related section of PHP-Manual to detect the reason for this error. In the most cases a misformed SQL statment. Ie. using LIMIT in a SQL-Statment for an Oracle database.

Заметка

Эта функция не должна вызываться статически.

Пример

Пример 35-1. Using getOne()


<?php
// Once you have a valid DB object named $db...
$data =& $db->getOne('SELECT cf FROM foo');

if (PEAR::isError($data)) {
    die($data->getMessage());
}

echo "$data\n";
?>

Пример 35-2. Using getOne() with one placeholder 


<?php
// Once you have a valid DB object named $db...
$data =& $db->getOne('SELECT cf FROM foo WHERE nf = ?',
        5);

if (PEAR::isError($data)) {
    die($data->getMessage());
}

echo "$data\n";
?>

Пример 35-3. Using getOne() with two placeholders 


<?php
// Once you have a valid DB object named $db...
$data =& $db->getOne('SELECT cf FROM foo WHERE nf IN (?, ?)',
        array(5, 10));

if (PEAR::isError($data)) {
    die($data->getMessage());
}

echo "$data\n";
?>

См. также

getRow(), getCol(), getAssoc(), getAll(), query(), "Intro - Prepare & Execute"

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User Notes:
Note by: webmaster@metapundit.net
2007-04-20 17:50 UTC
Be careful using getOne() on columns that may contain null values - you now have no way of knowing whether your query matched any rows or not. Consider the table

users
|id|name|
---+----+
1 | test
2 | NULL
---------
<?php
var_dump($db->getOne('select name from users where id=1'));
var_dump($db->getOne('select name from users where id=2'));
var_dump($db->getOne('select name from users where foo=1'));
?>

will output "NULL", "NULL", and a db_error object.