How to create foreign key in Wordpress database?

mysql, wordpress

Solution

Foreign keys work like this:

`FOREIGN KEY(table_field_name) REFERENCES [table_to_be_referred](referred_field)`

The field must exist in the referring table and must match exactly the definition of the referrer. Usually only primary keys are referred, due to their uniqueness.

Here's an example:

CREATE TABLE A (
    id INT NOT NULL PRIMARY KEY,
    name VARCHAR(10)
);

CREATE TABLE B (
    idB INT NOT NULL PRIMARY KEY,
    idA INT NOT NULL,
    name VARCHAR(10),
    FOREIGN KEY (idA) REFERENCES A(id)
);

Problem

I'm trying to make 3 database tables in Wordpress 1 of them I want to have relations from the other..but I cant find how to make reference keys and stuff in wordpress. With this code I create on table.. but how to make references and keys cause 1 table will contain the relation between two tables. ``` global $wpdb; $table_name = $wpdb -> prefix . "Person"; if($wpdb ->get_var("SHOW TABELS LIKE '$table_name'") != $table_name) { $sql = "CREATE TABLE " . $table_name . " ( `id` INTEGER(9) NOT NULL AUTO_INCREMENT, `titel` varchar(255) NOT NULL, `content` text NOT NULL, UNIQUE KEY id (id) );"; require_once(ABSPATH . 'wp-admin/includes/upgrade.php'); dbDelta($sql); add_option('createTBL_version', '1.0'); } ```

Original source