How to Use mysqli_insert_id() to Manage Database Relationships?

mysqli_insert_id: Retrieving Last Inserted ID for Database Relationships

In database-driven applications, it's often necessary to establish relationships between records in different tables. When inserting a record into one table, you may need to retrieve the ID of that record to associate it with related data in other tables.

The MySQLi library provides the mysqli_insert_id() function to retrieve the auto-incremented ID of the last inserted record. However, it's important to note that your database table must have an auto-increment field designated for this purpose.

To obtain the last inserted ID, you can use the following code snippet:

$last_id = mysqli_insert_id($mysqli);

Replace $mysqli with your MySQLi connection object. The $last_id variable will contain the ID of the last inserted record.

In your specific case, where you want to associate an image with a user's information, you can retrieve the last inserted ID from the table2 and use it to insert the corresponding data into table1.

Here's how you can do that:

$last_id = mysqli_insert_id($mysqli); // Retrieve the last inserted ID from table2

$stmt = $mysqli->prepare("
 insert into table1 (username, firstname, lastname, image) 
 select ?,?,?,image from table2 t2 where username = ? and  t2.id = ? 
");
$stmt->bind_param('sssss', $username, $fname, $lname, $username, $last_id);
$stmt->execute();

By using the mysqli_insert_id() function, you can ensure that your data relationships are properly established, allowing you to access and manipulate related records efficiently.

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