Generating link during fetch vs during creation - php

Question

Suppose I a table like this:
Categories:
| cat_id | cat_name |
|--------|----------|
| 1 | tvs |
| 2 | phones |
| 3 | tablets |
And then I have:
Products:
| product_id | product_name | product_category |
|------------|-----------------|------------------|
| 1 | tv sony | 1 |
| 2 | tv samsung | 1 |
| 3 | phone htc | 2 |
| 4 | phone motorolla | 2 |
| 5 | tablet apple | 3 |
And someone goes into index.php where I get 10 random products from the DB. For creating the link I'd have to fetch the database again (to get the name of the category) and then I could do something like mysite.com/phones/4 (that would be the link to phone motorolla).
Of course 10 wouldn't be too hard on the server but it's still another fetch on the database.
The other option is to fetch for the category name during the product creation, and generate a link there, something like:
| product_id | product_name | product_category | product_link |
|------------|-----------------|------------------|--------------|
| 1 | tv sony | 1 | tvs/1 |
| 2 | tv samsung | 1 | tvs/2 |
| 3 | phone htc | 2 | phones/3 |
| 4 | phone motorolla | 2 | phones/4 |
| 5 | tablet apple | 3 | tablets/5 |
However the name of the category may change and so the link wouldn't work anymore. So what should I do? Is there another way to do this?

Answer 1

Alright Nick so in SQL you have something very powerful called JOIN. A join in SQL allows you to merge columns from different tables based on a key. Usually the key is a primary key or a foreign key.
In your case, it seems you have as primary keys : cat_id and product_id
And as foreign key you have : product_category
Based on your database schema, you can query your tables like this :
SELECT p.product_id, p.product_name, c.cat_name
FROM PRODUCTS p INNER JOIN CATEGORIES c
ON p.product_category = c.cat_id
With this query you retrieve your product_id, product_name and cat_name based with only one query for your database.
Here is more info about joins in SQL => https://www.w3schools.com/sql/sql_join.asp
Hope it will help you.