This function cannot be used with any queries that return results. This includes SELECT, OPTIMIZE TABLE, etc.
(PHP 5 >= 5.1.0, PHP 7, PECL pdo >= 0.1.0)
PDO::exec — Execute an SQL statement and return the number of affected rows
$statement
)PDO::exec() executes an SQL statement in a single function call, returning the number of rows affected by the statement.
PDO::exec() does not return results from a SELECT statement. For a SELECT statement that you only need to issue once during your program, consider issuing PDO::query(). For a statement that you need to issue multiple times, prepare a PDOStatement object with PDO::prepare() and issue the statement with PDOStatement::execute().
statementThe SQL statement to prepare and execute.
Data inside the query should be properly escaped.
PDO::exec() returns the number of rows that were modified or deleted by the SQL statement you issued. If no rows were affected, PDO::exec() returns 0.
This function may
return Boolean FALSE, but may also return a non-Boolean value which
evaluates to FALSE. Please read the section on Booleans for more
information. Use the ===
operator for testing the return value of this
function.
The following example incorrectly relies on the return value of PDO::exec(), wherein a statement that affected 0 rows results in a call to die():
<?php
$db->exec() or die(print_r($db->errorInfo(), true));
?>
Example #1 Issuing a DELETE statement
Count the number of rows deleted by a DELETE statement with no WHERE clause.
<?php
$dbh = new PDO('odbc:sample', 'db2inst1', 'ibmdb2');
/* Delete all rows from the FRUIT table */
$count = $dbh->exec("DELETE FROM fruit WHERE colour = 'red'");
/* Return number of rows that were deleted */
print("Deleted $count rows.\n");
?>
The above example will output:
Deleted 1 rows.
This function cannot be used with any queries that return results. This includes SELECT, OPTIMIZE TABLE, etc.
PDO::eval() might return `false` for some statements (e.g. CREATE TABLE) even if the operation completed successfully, when using PDO_DBLIB and FreeTDS. So it is not a reliable way of testing the op status.
PDO::errorInfo() can be used to test the SQLSTATE error code for '00000' (success) and '01000' (success with warning).
<?php
function execute(PDO $conn, $sql) {
$affected = $conn->exec($sql);
if ($affected === false) {
$err = $conn->errorInfo();
if ($err[0] === '00000' || $err[0] === '01000') {
return true;
}
}
return $affected;
}
?>
PDO::errorInfo(): http://php.net/manual/en/pdo.errorinfo.php
List of SQLSTATE Codes: http://www-01.ibm.com/support/knowledgecenter/SSGU8G_11.70.0/com.ibm.sqls.doc/ids_sqs_0809.htm
It's worth noting here, that - in addition to the hints given in docs up there - using prepare, bind and execute provides more benefits than multiply querying a statement: performance and security!
If you insert some binary data (e.g. image file) into database using INSERT INTO ... then it may boost performance of parsing your statement since it is kept small (a few bytes, only, while the image may be several MiBytes) and there is no need to escape/quote the file's binary data to become a proper string value.
And, finally and for example, if you want to get a more secure PHP application which isn't affectable by SQL injection attacks you _have to_ consider using prepare/execute on every statement containing data (like INSERTs or SELECTs with WHERE-clauses). Separating the statement code from related data using prepare, bind and execute is best method - fast and secure! You don't even need to escape/quote/format-check any data.
this function don't execute multi_query
to get it see SQLITE_EXEC comments there is an pereg function that get all queries and execute all then an return the last one
You can't use it not only with SELECT statement, but any statement that might return rows. "OPTIMIZE table" is such example (returns some rows with optimization status).
If you do, PDO will lock-up with the "Cannot execute queries while other unbuffered queries are active." nonsense.
I spent half a day trying to work out why I could not update my sqlite3 database from apache using the PHP PDO driver. I was getting NO error messages at all.
I could connect and select data, but not modify it.
It wasn't until I added the following line:
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);
after immediately opening the database, that I got a hint of what was happening.
filename: File3
dl_count: 100
( ! ) Warning: PDO::exec() [pdo.exec.html]: SQLSTATE[HY000]: General error: 8 attempt to write a readonly database in /www/htdocs/test/dl-counter/sqlite-readwrite-test.php on line 76
Call Stack
#
Time
Memory
Function
Location
1 0.0086 330120 {main}( ) ../sqlite-readwrite-test.php:0
2 0.0273 331240 PDO->exec( ) ../sqlite-readwrite-test.php:76
Affected Rows: ''
filename: File3
dl_count: 100
The problem was with the file permissions. As root I could read and write the database from the sqlite3 command line monitor. But Apache was unable to write the database.
Changed the permissions to 755 wwwrun:wwrun and it all works OK!
Thanks again :)
If you do this:
<?php
$res = $dbh->query("SELECT * FROM sessions WHERE session_id = '$p_sessID'");
$l_records = $res->fetch(PDO::FETCH_ASSOC);
if( $l_records ) {
// ...update session-data
$l_theQuery = "UPDATE sessions SET session_expires='$newExp', session_data='$p_sessData' WHERE session_id='$p_sessID'";
echo $l_theQuery;
$l_stmt = $this->db->prepare($l_theQuery);
if ( $l_stmt ) {
$l_rows = $l_stmt->execute();
}
}
?>
You will get nothing.
But do this:
<?php
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);
?>
Prior to the code above, you will get this:
"PDO::prepare(): SQLSTATE[HY000]: General error: 2014 Cannot execute queries while other unbuffered queries are active. Consider using PDOStatement::fetchAll(). Alternatively, if your code is only ever going to run against mysql, you may enable query buffering by setting the PDO::MYSQL_ATTR_USE_BUFFERED_QUERY attribute."
So, instead of fetch(), use fetchAll(), it will make you less insane.
Incidentally, the INSERT statement that I was issuing, if the record that I needed to update didn't yet exist, after the initial fetch() command worked perfectly.
Changing to fetchAll() fixed it.
For those that want an exec that handles params like prepare/execute does. You can simulate this with another function
<?php
class Real_PDO extends PDO {
public function execParams($sql, $params) {
$stm = $this->prepare($sql);
$result = false;
if( $stm && $stm->execute($params) ) {
$result = $stm->rowCount();
while( $stm->fetch(PDO::FETCH_ASSOC) ) {
}
}
return $result;
}
}
?>
Remember though, if you are doing a lot of inserts, you'll want to do it the manual way, as the prepare statement will speed up when doing multiple executes(inserts). I use this so I can place all my SQL statements in one place, and have auto safe quoting against sql-injections.
If you are wondering about the fetch after, remember some databases can return data SELECT-like data from REMOVE/INSERTS. In the case of PostgreSQL, you can have it return you all records that were actually removed, or have the insert return the records after the insert/post field functions, and io trigger fire, to give you normalized data.
<?php
define("BLAH_INSERT", "INSERT INTO blah (id,data) VALUES(?,?)");
$pdo = new Real_PDO("connect string");
$data = array("1", "2");
$pdo->execParams(BLAH_INSERT, $data);
?>
if a field's value is a string, u must use single quotes, for example:
update a set b = 'test' where id = 1
if u use update a set b = "test" where id = 1
it does not run as u expect
i do not know what the reason