In PHP and database systems, foreign key mapping refers to establishing a relationship between two database tables using foreign keys. Foreign keys are a fundamental concept in relational databases, allowing you to link one table’s field (or a set of fields) to the primary key in another table. This relationship ensures referential integrity, meaning that the data in the linked tables stays consistent and accurate.<\/p>\n
Step-by-step explanation of foreign key mapping in PHP with an example:<\/strong> In the orders table, the user_id column is a foreign key that references the id column in the users table. This establishes a relationship between the users and orders tables.<\/p>\n Step 2: PHP Code to Interact with the Database:<\/strong> In this example, when inserting data into the orders table, the user_id field is set to value 1, referencing the id of the \u201cabc\u201d user in the users table.<\/em><\/p>\n
\nStep 1: Create Database Tables:<\/em>
\nCREATE TABLE users (
\n id INT PRIMARY KEY,
\n username VARCHAR(50) NOT NULL
\n);
\nCREATE TABLE orders (
\n id INT PRIMARY KEY,
\n user_id INT,
\n order_details TEXT,
\n FOREIGN KEY (user_id) REFERENCES users(id)<\/strong>
\n);<\/code><\/p>\n
\nExample of Inserting Data:<\/em>
\n\/\/ Establish a database connection
\n$mysqli = new mysqli(\"localhost\", \"username\", \"password\", \"database_name\");
\n\/\/ Check the connection
\nif ($mysqli->connect_error)
\ndie(\"Connection failed: \" . $mysqli->connect_error);
\n}
\n\/\/ Insert data into users table
\n$username = \"abc\";
\n$sql = \"INSERT INTO users (id, username) VALUES (1, '$username')\";
\n$mysqli->query($sql);
\n\/\/ Insert data into orders table with a foreign key reference
\n$orderDetails = \"Sample order details\";
\n$sql = \"INSERT INTO orders (id, user_id, order_details) VALUES (1, 1, '$orderDetails')\";$mysqli->query($sql);
\n\/\/ Close the connection
\n$mysqli->close();<\/code><\/p>\n