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Statement¶
A Statement
object is returned by QueryBuilder->execute()
for ->select()
and ->count()
query types and by Connection->select()
and Connection->count()
calls.
The object represents a query result set and comes with methods to ->fetch()
single rows
or to ->fetchAll()
of them. Additionally, it can also be used to execute a single prepared
statement with different values multiple times. This part is however not widely used within
the TYPO3 CMS
core yet, and thus not fully documented here.
Note
The name "Statement" instead of "Result" can be puzzling at first glance: The class represents a prepared statement that can be executed multiple times with different values and then returns multiple different result sets. From this point of view "Statement" fits much better than "Result".
Warning
The return type of single field values is NOT type safe! If selecting a value from a field that is
defined as int
, the Statement
result may very well return that as PHP
string
. This is
true for other database column types like FLOAT
, DOUBLE
and others.
This is an issue with the database drivers used below, it may happen that MySQL
returns an integer
value for an int
field, while MSSQL
returns a string.
In general, the application must take care of an according type cast on their own to reach maximum
DBMS
compatibility.
fetch()¶
Fetch next row from a result statement. Usually used in while() loops. Typical example:
// use TYPO3\CMS\Core\Utility\GeneralUtility;
// use TYPO3\CMS\Core\Database\ConnectionPool;
// Fetch all records from tt_content on page 42
$queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable('tt_content');
$statement = $queryBuilder
->select('uid', 'bodytext')
->from('tt_content')
->where($queryBuilder->expr()->eq('pid', $queryBuilder->createNamedParameter(42, \PDO::PARAM_INT)))
->execute();
while ($row = $statement->fetch()) {
// Do something useful with that single $row
}
->fetch()
returns arrays with single field / values pairs until the end of the result set is reached
which then returns false and thus breaks the while loop.
fetchAll()¶
Returns an array containing all of the result set rows by implementing the same while loop as above internally.
Using that method saves some precious code characters but is more memory intensive if the result set is large
with lots of rows and lot of data since big arrays are carried around in PHP
:
// use TYPO3\CMS\Core\Utility\GeneralUtility;
// use TYPO3\CMS\Core\Database\ConnectionPool;
// Fetch all records from tt_content on page 42
$queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable('tt_content');
$rows = $queryBuilder
->select('uid', 'bodytext')
->from('tt_content')
->where($queryBuilder->expr()->eq('pid', $queryBuilder->createNamedParameter(42, \PDO::PARAM_INT)))
->execute()
->fetchAll();
fetchColumn()¶
Returns a single column from the next row of a result set, other columns from that result row are discarded.
This method is especially handy for QueryBuilder->count()
queries. The Connection->count()
implementation
does exactly that to return the number of rows directly:
// use TYPO3\CMS\Core\Utility\GeneralUtility;
// use TYPO3\CMS\Core\Database\ConnectionPool;
// Get the number of tt_content records on pid 42 into variable $numberOfRecords
$queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable('tt_content');
$numberOfRecords = $queryBuilder
->count('uid')
->from('tt_content')
->where($queryBuilder->expr()->eq('pid', $queryBuilder->createNamedParameter(42, \PDO::PARAM_INT)))
->execute()
->fetchColumn(0);
rowCount()¶
Returns the number of rows affected by the last execution of this statement. Use that method
instead of counting the number of records in a ->fetch()
loop manually.
Warning
->rowCount()
works well with DELETE
, UPDATE
and INSERT
queries. However, it does NOT
return a valid number for SELECT
queries on some DBMS
. Never use ->rowCount()
on SELECT
queries. This may work with MySOL, but fails with other databases like SQLite.
Re-use Prepared Statement()¶
Doctrine usually prepares a statement first, and then executes it with given parameters. Implementing prepared statements depends on the given driver. A driver not properly implementing prepared statements fall back to a direct execution of given query.
There is an API to make real use of prepared statements that becomes handy if the same query is executed
with different arguments over and over again. The example below prepares a statement to the pages
table
and executes it twice with different arguments:
// use TYPO3\CMS\Core\Utility\GeneralUtility;
// use TYPO3\CMS\Core\Database\ConnectionPool;
$connection = GeneralUtility::makeInstance(ConnectionPool::class)->getConnectionForTable('pages');
$queryBuilder = $connection->createQueryBuilder();
$queryBuilder->getRestrictions()->removeAll();
$sqlStatement = $queryBuilder->select('uid')
->from('pages')
->where($queryBuilder->expr()->eq('uid', $queryBuilder->createPositionalParameter(0, \PDO::PARAM_INT)))
->getSQL();
$statement = $connection->executeQuery($sqlStatement, [ 24 ]);
$result1 = $statement->fetch();
$statement->closeCursor(); // free the resources for this result
$statement->bindValue(1, 25);
$statement->execute();
$result2 = $statement->fetch();
$statement->closeCursor(); // free the resources for this result
Looking at a mysql debug log:
Prepare SELECT `uid` FROM `pages` WHERE `uid` = ?
Execute SELECT `uid` FROM `pages` WHERE `uid` = '24'
Execute SELECT `uid` FROM `pages` WHERE `uid` = '25'
The log shows one statement preparation with two executions.