使用许多外键在MySql中创建大表

Question

I am creating an App where I have to save Information About User Educations then I am going to show it to them. Each user may have 1, 2 or more Educations. I am creating this table with laravel Schema builder. Here is code

    Schema::create('educations', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('user_id')->unsigned();
        $table->date('from')->nullable();
        $table->date('to')->nullable();
        $table->integer('country_id')->unsigned();
        $table->integer('city_id')->unsigned();
        $table->integer('university_id')->unsigned();
        $table->integer('faculty_id')->unsigned()->nullable();
        $table->integer('speciality_id')->unsigned()->nullable();
        $table->integer('degree_id')->unsigned()->nullable();
        $table->string('image', 100)->nullable();
        $table->text('additional')->nullable();


        $table->index('university_id');
        $table->index('faculty_id');
        $table->index('country_id');
        $table->index('city_id');
        $table->index('degree_id');
        $table->index('speciality_id');


        $table->foreign('user_id')
            ->references('id')->on('users')
            ->onDelete('cascade');

        $table->foreign('faculty_id')
            ->references('id')->on('faculties')
            ->onDelete('cascade');

        $table->foreign('degree_id')
            ->references('id')->on('degrees')
            ->onDelete('cascade');

        $table->foreign('speciality_id')
            ->references('id')->on('specialities')
            ->onDelete('cascade');

        $table->foreign('university_id')
            ->references('id')->on('universities')
            ->onDelete('cascade');

        $table->foreign('country_id')
            ->references('id')->on('countries')
            ->onDelete('cascade');

        $table->foreign('city_id')
            ->references('id')->on('cities')
            ->onDelete('cascade');
    });

MySql Code:

CREATE TABLE `educations` 
( 
    `id`            INT UNSIGNED NOT NULL auto_increment PRIMARY KEY, 
    `user_id`       INT UNSIGNED NOT NULL, 
    `from`          DATE NULL, 
    `to`            DATE NULL, 
    `country_id`    INT UNSIGNED NOT NULL, 
    `city_id`       INT UNSIGNED NOT NULL, 
    `university_id` INT UNSIGNED NOT NULL, 
    `faculty_id`    INT UNSIGNED NULL, 
    `speciality_id` INT UNSIGNED NULL, 
    `degree_id`     INT UNSIGNED NULL, 
    `image`         VARCHAR(100) NULL, 
    `additional`    TEXT NULL 
) 

DEFAULT CHARACTER SET utf8mb4 COLLATE 'utf8mb4_unicode_ci') 

So i have a question: when I want to get all Education of One user I hae to run join on almost 7 table or use laravel query builder and run many query when page loads. Is my database design Correct?

the reason why I am using foreign keys on each column is users must choose their faculties, universities, specialities and etc from my list in database which is variable.

any answer will help. thanks..

Answer 1

I believe I can see your idea behind these relational structures but in my humble opinion, they are not quite correct because I feel like in some cases the column entries are not directly related with each other. I will give you some examples:

1. Your table name is 'educations'. 1 user has got several educations but 1 education is not only reserved for 1 user. So this is an n:m-relation, which is why you need 1 table called 'educations', 1 for 'users' and 1 table in between those called 'user_has_got_education', for example. Your foreign keys land in the latter table with user_id and education_id.
2. country_id, city_id, university_id, faculty_id have got no direct relation to educations. Create a table called 'countries'(country_id, country_name, country_population, country_code,.....), then create a table called 'cities' in the same way. Here it gets a bit more difficult because one city_id is not necessarily distinct as there could be TWO city_ids with the city_name='London', one referring to London(UK), one to London(USA, Ohio) and one to London(USA, Kentucky). So what you need here is at least a table relation to 'countries' AND a state/county/shire - and even that might not be enough (if there were 2 cities called 'London' in the USA in Ohio state, for example). I call this 'direct relations'. In short, your columns (foreign keys) are in the wrong place, they belong into a 'directly connected brother table', not > into a 'nephew table'.

Try to get from one logical direct relation to another and 'connect' your tables accordingly. I hope I could help a bit, can't really give you a full table structure here, though.