Not able to set foreign key in Laravel

Question

I am trying to reference the 'title' column of questions_solutions_language table to the 'title' column of questions table but i am not able to do so

My questions_solutions_language migration

public function up()
    {
        Schema::create('questions_solutions_language', function (Blueprint $table) {
            $table->id();
            $table->string('title');
            $table->string('language');
            $table->text('solution');
            $table->timestamps();
        });

        Schema::table('questions_solutions_language', function($table)
        {
            $table->foreign('title')
            ->references('title')->on('questions')
            ->onDelete('cascade');
        });
    }

My Questions migration:

  $table->id();
            $table->string('title');
            $table->string('url');
            $table->string('category');
            $table->string('difficulty');
            $table->string('languages')->nullable(true);
            $table->timestamps();

I tried referencing the id column of questions_solutions_language to the id column of questions and it works fine. But as soon as i try to reference the string column i get error. I also tried doing the migrations separately still it doesnt work. Any help will be greatly appreciated

it is because foreign id columns in laravel are supposed to be unsigned big integer, since id column is unsignedbigint then it works. I'd also suggest use $table->foreignIdFor('table') instead of doing this manually. — Sumit kumar, Feb 20 '23 at 13:56
Thank you for your response. Is there no way to set strings as foreign key then? — , Feb 20 '23 at 13:57
no that's not how mysql foreign keys are supposed to work you can use ID's for it and work with it. — Sumit kumar, Feb 20 '23 at 14:01
As long I know foreign keys are based in primary keys. Maybe this explanation gives you more details https://stackoverflow.com/questions/4813727/is-string-or-int-preferred-for-foreign-keys — Farid, Feb 20 '23 at 14:05
So are you saying i should set my primary key to string column and then try again? — , Feb 20 '23 at 14:10
yes if you make title primary and remove $table->id() in question can work but keep in mind storing same strings on 2 tables is not a good practice and bad for db normalization (3NF) ie "3NF is used to reduce the data duplication." for reference: https://stackoverflow.com/questions/723998/what-are-database-normal-forms-and-can-you-give-examples — Sumit kumar, Feb 20 '23 at 14:21

score 0 · Accepted Answer · answered Feb 20 '23 at 14:26

0

You can use string column as foreign key, but your questions.title column should have unique index.

answered Feb 20 '23 at 14:26

katsarov

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Not able to set foreign key in Laravel

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