How to Create a virtual calculated column in Laravel Migration from another table?

Question

Table to be created the virtual calculated column. The total column is just an example of what I expect

Schema::create('products', function (Blueprint $table) {
    $table->id();
    $table->string('name');
    $table->integer('price');
    $table->integer('total')->virtualAs(sum(lots.total))->defalt(0); // virtualAs Or virtualAs
});

Second table

Schema::create('lots', function (Blueprint $table) {
    $table->id();
    $table->string('description');
    $table->decimal('price');
    $table->integer('total') ;
    $table->integer('product_id'); //relationship
});

I would like to obtain the sum of the lots in the total product column

You can just run two migrations and then run the seeder, which will fill the needed field — V-K, Nov 03 '20 at 15:11
Take a look at this: https://stackoverflow.com/questions/38448583/subquery-as-generated-column-in-mysql — Chin Leung, Nov 03 '20 at 15:20
thank you @ChinLeung ! You helped a lot with this post. I'll change the concept regarding the use of virtual columns. — Rafael Furtado, Nov 03 '20 at 15:30

score 0 · Answer 1 · answered Nov 03 '20 at 15:16

0

The total should not be stored in the Db since it is redundant and can be calculated.
You should create your table and your models with the relationship for each others.
Then use the ->withCount() method to count the related lots of products.

Ex: Product::withCount('lots')->get() this will give you the number of lots associated with each product

answered Nov 03 '20 at 15:16

ml59

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How do I calculate a column from the lots table with withCount ()? Can you give an example? – Rafael Furtado Nov 03 '20 at 15:50
Have a look here https://laravel.com/docs/8.x/eloquent-relationships#counting-related-models – ml59 Nov 03 '20 at 16:00

How to Create a virtual calculated column in Laravel Migration from another table?

1 Answers1