How to start and end transaction in mysqli?

问题

As far as I understood transaction starts once we call $mysqli->autocommit(FALSE); statement and ends after calling $mysqli->commit(); command like in the example below.

<?php
//Start transaction 
$mysqli->autocommit(FALSE);
$mysqli->query('UPDATE `table` SET `col`=2');
$mysqli->query('UPDATE `table1` SET `col1`=3;');
$mysqli->commit();
//End transaction

//Executing other queries without transaction control
$mysqli->query("Select * from table1");
$mysqli->query("Update table1 set col1=2");
//End of executing other queries without transaction control

//Start transaction 
$mysqli->autocommit(FALSE);
$mysqli->query('UPDATE `table` SET `col`=2');
$mysqli->query('UPDATE `table1` SET `col1`=3;');
$mysqli->commit();
//End transaction
?>

Have I understood correctly? If not could you please correct me, because it is actually my first time using transactions in real life.

Thank you.

回答1:

Well according to the php doc, you're right.

<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

$mysqli->query("CREATE TABLE Language LIKE CountryLanguage");

/* set autocommit to off */
$mysqli->autocommit(FALSE);

/* Insert some values */
$mysqli->query("INSERT INTO Language VALUES ('DEU', 'Bavarian', 'F', 11.2)");
$mysqli->query("INSERT INTO Language VALUES ('DEU', 'Swabian', 'F', 9.4)");

/* commit transaction */
$mysqli->commit();

/* drop table */
$mysqli->query("DROP TABLE Language");

/* close connection */
$mysqli->close();
?>

In the example above:

the CREATE TABLE is auto committed because it's the default behaviour.
the INSERT INTO aren't auto committed because of the autocommit(FALSE).
the DROP TABLE is auto committed because the autocommit(FALSE) was reset by the ->commit();.

回答2:

j0k is mainly right, except in the drop table.

The auto commit is not turned on with the ->commit()

Instead, the DROP TABLE is a DDL query, and DDL queries are always implicitly committed and will commit all your previously non committed work.

So, if you did not commit the work, the DDL query would force this commit.

回答3:

Prepare SQL statement ONCE, and then execute it SEVERAL times:

<?php
$Mysqli = new mysqli("host","user","pass","base");

// check connection
if(mysqli_connect_errno())
{
  printf("Connect failed: %s\n",mysqli_connect_error());
  exit();
}

// some data for db insertion
$countries=['Austria','Belgia','Croatia','Denmark','Estonia'];

// explicitly begin DB transaction
$Mysqli->begin_transaction();

// prepare statement (for multiple inserts) only once
$stmt=$Mysqli->prepare("INSERT INTO table(column) VALUES(?)");

// bind (by reference) prepared statement with variable $country
$stmt->bind_param('s',$country);

// load value from array into referenced variable $country
foreach($countries as $country)
{
  //execute prep stat more times with new values
  //$country is binded (referenced) by statement
  //each execute will get new $country value
  if(!$stmt->execute())
  {
    // rollback if prep stat execution fails
    $Mysqli->rollback();
    // exit or throw an exception
    exit();
  }
}

// close prepared statement
$stmt->close();

// commit transaction
$Mysqli->commit();

// close connection
$Mysqli->close();

?>

回答4:

You think that commit automatically switches autocommit back to true? A comment in the PHP Doc says NO!

来源：https://stackoverflow.com/questions/12091971/how-to-start-and-end-transaction-in-mysqli

标签

php

transactions

mysqli