PDOStatement::getColumnMeta
(PHP 5 >= 5.1.0, PECL pdo >= 0.2.0)
PDOStatement::getColumnMeta — Returns metadata for a column in a result set
Description
$column
)This function is EXPERIMENTAL. The behaviour of this function, its name, and surrounding documentation may change without notice in a future release of PHP. This function should be used at your own risk.
Retrieves the metadata for a 0-indexed column in a result set as an associative array.
Not all PDO drivers support PDOStatement::getColumnMeta().
Parameters
-
column -
The 0-indexed column in the result set.
Return Values
Returns an associative array containing the following values representing the metadata for a single column:
| Name | Value |
|---|---|
| native_type | The PHP native type used to represent the column value. |
| driver:decl_type | The SQL type used to represent the column value in the database. If the column in the result set is the result of a function, this value is not returned by PDOStatement::getColumnMeta(). |
| flags | Any flags set for this column. |
| name | The name of this column as returned by the database. |
| table | The name of this column's table as returned by the database. |
| len | The length of this column. Normally -1 for types other than floating point decimals. |
| precision | The numeric precision of this column. Normally 0 for types other than floating point decimals. |
| pdo_type | The type of this column as represented by the PDO::PARAM_* constants. |
Returns FALSE if the requested column does not exist in the result set,
or if no result set exists.
Changelog
| Version | Description |
|---|---|
| 5.2.3 | table field |
Examples
Example #1 Retrieving column metadata
The following example shows the results of retrieving the metadata for a single column generated by a function (COUNT) in a PDO_SQLITE driver.
<?php
$select = $DB->query('SELECT COUNT(*) FROM fruit');
$meta = $select->getColumnMeta(0);
var_dump($meta);
?>
The above example will output:
array(6) {
["native_type"]=>
string(7) "integer"
["flags"]=>
array(0) {
}
["name"]=>
string(8) "COUNT(*)"
["len"]=>
int(-1)
["precision"]=>
int(0)
["pdo_type"]=>
int(2)
}
See Also
- PDOStatement::columnCount() - Returns the number of columns in the result set
- PDOStatement::rowCount() - Returns the number of rows affected by the last SQL statement
- PHP Руководство
- Функции по категориям
- Индекс функций
- Справочник функций
- Расширения для работы с базами данных
- Уровни абстракции
- Объекты данных PHP
- Функция PDOStatement::bindColumn() - Связывает столбец с PHP переменной
- Функция PDOStatement::bindParam() - Привязывает параметр запроса к переменной
- Функция PDOStatement::bindValue() - Связывает параметр с заданным значением
- Функция PDOStatement::closeCursor() - Закрывает курсор, переводя запрос в состояние готовности к повторному запуску
- Функция PDOStatement::columnCount() - Возвращает количество столбцов в результирующем наборе
- Функция PDOStatement::debugDumpParams() - Вывод информации о подготовленной SQL команде в целях отладки
- Функция PDOStatement::errorCode() - Определяет SQLSTATE код соответствующий последней операции объекта PDOStatement
- PDOStatement::errorInfo
- Функция PDOStatement::execute() - Запускает подготовленный запрос на выполнение
- Функция PDOStatement::fetch() - Извлечение следующей строки из результирующего набора
- Функция PDOStatement::fetchAll() - Возвращает массив, содержащий все строки результирующего набора
- Функция PDOStatement::fetchColumn() - Возвращает данные одного столбца следующей строки результирующего набора
- Функция PDOStatement::fetchObject() - Извлекает следующую строку и возвращает ее в виде объекта
- Функция PDOStatement::getAttribute() - Получение значения атрибута запроса PDOStatement
- Функция PDOStatement::getColumnMeta() - Возвращает метаданные столбца в результирующей таблице
- Функция PDOStatement::nextRowset() - Переход к следующему набору строк в результате запроса
- Функция PDOStatement::rowCount() - Возвращает количество строк, модифицированных последним SQL запросом
- Функция PDOStatement::setAttribute() - Присваивает атрибут объекту PDOStatement
- Функция PDOStatement::setFetchMode() - Задает режим выборки по умолчанию для объекта запроса
Коментарии
I found a short discussion related to this function at
http://www.sitepoint.com/forums/showthread.php?t=497257
I haven't tried it (yet?) but hopefully someone can find it useful.
This method is supported in the MySQL 5.0+ driver. It can be used for object hydration:
<?php
$pdo_stmt = $dbh->execute('SELECT discussion.id, discussion.text, comment.id, comment.text FROM discussions LEFT JOIN comments ON comment.discussion_id = discussion.id');
foreach(range(0, $pdo_stmt->columnCount() - 1) as $column_index)
{
$meta[] = $pdo_stmt->getColumnMeta($column_index);
}
while($row = $pdo_stmt->fetch(PDO::FETCH_NUM))
{
foreach($row as $column_index => $column_value)
{
//do something with the data, using the ids to establish the discussion.has_many(comments) relationship.
}
}
?>
If you are building an ORM, this method is very useful to support more natural SQL syntax. Most ORMs require the column names to be aliases so that they can be parsed and turned into objects that properly represent has_one, has_many, many_to_many relationships.
native_type has the following mapping for MySQL:
(tested in PHP 5.4, MySQL 5.7)
INT(11) (PKs) => LONG
TINYINT(4) => TINY
DOUBLE => DOUBLE
VARCHAR => VAR_STRING
CHAR => STRING
DATE => DATE
Functions => VAR_STRING
- DATEFORMAT()
- CONCAT()
I recently added a note to a small function that went through the results of PDOStatement::fetch and mapped columns to integer or float types.
I forgot to test for columns that can have a null value!
I'm updating the code here, sorry.
This website doesn't let me edit the original comment, so I'm just gonna link to a gist in case it needs even further fixes.
https://gist.github.com/AeonFr/db3b2a8a95753076d9e4da42d29365d2
I basically added this code:
<?php
if ($value === null) {
continue;
}
?>
This method is supported by sql server too (at least the version of the PDO driver 5.7.1)
Example:
array(8) {
["flags"]=>
int(0)
["sqlsrv:decl_type"]=>
string(12) "int identity"
["native_type"]=>
string(6) "string"
["table"]=>
string(0) ""
["pdo_type"]=>
int(2)
["name"]=>
string(8) "IdCompra"
["len"]=>
int(10)
["precision"]=>
int(0)
}
Searching for LONGLONG in php-src:
$datatypes = array(
MYSQLI_TYPE_TINY => "TINY",
MYSQLI_TYPE_SHORT => "SHORT",
MYSQLI_TYPE_LONG => "LONG",
MYSQLI_TYPE_FLOAT => "FLOAT",
MYSQLI_TYPE_DOUBLE => "DOUBLE",
MYSQLI_TYPE_TIMESTAMP => "TIMESTAMP",
MYSQLI_TYPE_LONGLONG => "LONGLONG",
MYSQLI_TYPE_INT24 => "INT24",
MYSQLI_TYPE_DATE => "DATE",
MYSQLI_TYPE_TIME => "TIME",
MYSQLI_TYPE_DATETIME => "DATETIME",
MYSQLI_TYPE_YEAR => "YEAR",
MYSQLI_TYPE_ENUM => "ENUM",
MYSQLI_TYPE_SET => "SET",
MYSQLI_TYPE_TINY_BLOB => "TINYBLOB",
MYSQLI_TYPE_MEDIUM_BLOB => "MEDIUMBLOB",
MYSQLI_TYPE_LONG_BLOB => "LONGBLOB",
MYSQLI_TYPE_BLOB => "BLOB",
MYSQLI_TYPE_VAR_STRING => "VAR_STRING",
MYSQLI_TYPE_STRING => "STRING",
MYSQLI_TYPE_NULL => "NULL",
MYSQLI_TYPE_NEWDATE => "NEWDATE",
MYSQLI_TYPE_INTERVAL => "INTERVAL",
MYSQLI_TYPE_GEOMETRY => "GEOMETRY",
);