Multiple query PHP Mysql [duplicate] - php

Question

I want to run mysql queries to insert data from a custom html form.
Here I have to insert multiple set of data, some data to one table and some to other. Currently I am using the simple approach to send data to php page using jquery ajax and run multiple mysqli_query() functions one after another. But I guess when there will be large number of users, there will be problems related to speed. So can anyone suggest me a better way to do the same.
There are 5 tables in the database and each table has 7 to 10 columns that need to get different set of data, every time.
I want to run each query only if the previous insert query is successfully completed.
That's why I am checking for the result every time and then running the next query, which makes me feel the issue of speed on large user base.

Answer 1

The problem is, I need to insert data to first table and if its successfully inserted then only run query for the second table.
This means you need a transaction.
A transaction is a set of queries that either all execute ok or if one fails - they all fail. This is to ensure you don't end up with crap data in your tables.
Do not
Do not use multiquery.
Do not use mysql_* function(s).
Do not use bulk inserts.
People telling you to do that just have absolutely no clue what they're doing, ignore them.
Do
Use PDO
Use prepared statements
Prepare the statement(s) ONCE, use them MULTIPLE times
Sample code - do NOT copy paste
$dsn = 'mysql:dbname=testdb;host=127.0.0.1;charset=utf8mb4';
$user = 'dbuser';
$password = 'dbpass';
$pdo = new PDO($dsn, $user, $password);
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$insert['first'] = $pdo->prepare("INSERT INTO table SET col1 = :val, col2 = :val2");
$insert['second'] = $pdo->prepare("INSERT INTO another_table SET col1 = :val, col2 = :val2");
$pdo->beginTransaction();
$insert['first']->bindValue(':val', 'your value');
$insert['first']->bindValue(':val2', 'anothervalue');
$insert['first']->execute();
$insert['second']->bindValue(':val', 'your value');
$insert['second']->bindValue(':val2', 'anothervalue');
$insert['second']->execute();
$pdo->commit();
The code above will save the data in two tables ONLY if both inserts are successful.

Answer 2

To paraphrase the accepted answer but with accent on mysqli.
The key is to configure mysqli to throw exceptions and to use a transaction.
A transaction will ensure that all operations either complete in their entirety or have no effect whatsoever. Another important advantage of using a transaction is that it makes multiple inserts faster, eliminating all possible delays that could be caused by separate query execution.
To use transactions with mysqli you need to do as follows:
First of all, make sure you have a proper mysqli connection, which, among other things, tells mysqli to throw an exception in case of error. Then just prepare your queries, start a transaction, execute the queries and commit the transaction - just like it is shown in the accepted answer, but with mysqli:
include 'mysqli.php';
$stmt1 = $mysqli->prepare("INSERT INTO table SET col1 = ?, col2 = ?");
$stmt2 = $mysqli->prepare("INSERT INTO another_table SET col1 = ?, col2 = ?");
$mysqli->begin_transaction();
$stmt1->bind_param("ss", $col1, $col2);
$stmt1->execute();
$stmt2->bind_param("ss", $col1, $col2);
$stmt2->execute();
$mysqli->commit();
Thanks to exceptions and transactions there is no need to verify the result of each query manually.