How to add unique constraint to an existing foreignId column in laravel?

Question

I have an existing table in database with data and I want to add unique constraints to the customer_id column in it.

I tried doing $table->foreignId('customer_id)->unique()->change(). But it doesn't seem to work. The same works for any non foreign fields like string and int.

Error:

SQLSTATE[42S21]: Column already exists: 1060 Duplicate column name 'customer_id' (SQL: alter table `partner_preferences` add `customer_id` bigint unsigned not  

null)

Answer 1

foreignId() essentially creates a new column which in your case already exists.

The foreignId method is an alias of the unsignedBigInteger method:

laravel - difference between foreignId() and unsignedBigInteger()

Try this please:

Unique constraint

    public function up()
    {
        // Change the 'table name' according to your needs.
        Schema::table("employees", function (Blueprint $table) {

            $table->unique('customer_id');
        });
    }

WARNING: Make sure the column(s) that you're applying this constraint to is actually unique. (Must have unique data.)

Otherwise, an error (SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '1' for key 'XXXX_customer_id_unique') will be thrown.