How I can get an auto incremented value - sql

Question

I have here a table that corresponds to the orders of the customers. I use AUTO_INCREMENT to determine the ID of the order. I have this SQL code to the orders table:
CREATE TABLE IF NOT EXISTS `orders` (
`order_id` int(11) NOT NULL AUTO_INCREMENT,
`customer_id` int(11) NOT NULL,
`customer_name` varchar(500) NOT NULL,
`order_total_price` decimal(20, 2) NOT NULL,
`order_date` varchar(100) NOT NULL,
PRIMARY KEY (`order_id`)
) ENGINE=InnoDB
What I need is to insert each of the products of that order in another table with a Foreign Key order_id to specify what order that products belongs to. The SQL code for the purchased_products table is:
CREATE TABLE IF NOT EXISTS `purchased_products` (
`order_id` int (11) NOT NULL,
FOREIGN KEY (`order_id`) REFERENCES orders(`order_id`),
`product_name` varchar(500) NOT NULL,
`product_price` decimal(20, 2) NOT NULL,
`product_quantity` int(11) NOT NULL,
PRIMARY KEY (`order_id`)
)
When the user buy something, I use this to insert the data in the orders table:
INSERT INTO orders (customer_id, customer_name, order_total_price, order_date)
VALUES ('{$customer_id}', '{$customer['customer_name']}', '{$order_total_price}', '{$order_date}')";
And here is my problem. I need to insert in the purchased_products table the products with the Order ID generated:
INSERT INTO purchased_products (order_id, product_name, product_price, product_quantity)
VALUES ('*/The ID of the order need to goes here*/', '{$product['product_name']}', '{$product['product_price']}', '{$product['quantity']}')";
This is giving me a headache. I'm not really knowing how to do it. This should be done by a different way? How do I associate the order ID to the products belonging to it?

Answer 1

use function last_insert_id(). it will give you value that was auto-incremented as last one before call to it.

Answer 2

You can get the get the last inserted primary key value by using ##IDENTITY
Here's the MSDN article: https://msdn.microsoft.com/en-us/library/ms187342.aspx
USE AdventureWorks2012;
GO
--Display the value of LocationID in the last row in the table.
SELECT MAX(LocationID) FROM Production.Location;
GO
INSERT INTO Production.Location (Name, CostRate, Availability, ModifiedDate)
VALUES ('Damaged Goods', 5, 2.5, GETDATE());
GO
SELECT ##IDENTITY AS 'Identity';
GO
--Display the value of LocationID of the newly inserted row.
SELECT MAX(LocationID) FROM Production.Location;
GO
I would also recommend wrapping the statement in a TRANSACTION so that if any errors occur you can rollback.

Answer 3

As others have commented it depends on the RDBMS. In Oracle you typically use sequences. You create and store the sequence on the database and can use it on an INSERT by doing sequencename.nextval().
Sequences let you control starting values, increment/decrement size, caching and a lot more.

Answer 4

I did it by using PDO lastInsertId() to get the ID of last inserted order:
$sql = "INSERT INTO orders (customer_id, customer_name, order_total_price, order_date)
VALUES ('{$customer_id}', '{$customer['customer_name']}', '{$order_total_price}', '{$order_date}')";
$query = $connection->prepare($sql);
$query->execute();
$respective_order_id = $connection->lastInsertId();
And then:
INSERT INTO purchased_products (order_id, product_name, product_price, product_quantity)
VALUES ('{$respective_order_id}', '{$product['product_name']}', '{$product['product_price']}', '{$product['quantity']}')";
Thanks for all who tried to help! They put me in the right way!

Answer 5

you can use SCOPE_IDENTITY() to retrieve the last identity you inserted within the current sql session.
here is another question with a great description of all the differences:
identity scope Question