Display categories being supplied by a supplier - php

Question

I have my 2 tables : tbl_supplier & tbl_categories
I want to display all the categories being supplied by a supplier in a dropdown select option in php html
Example:
Supplier1 > Category1, Category2, Category3
Supplier2 > Category2, Category4

Answer 1

You need a third table with one row per Supplier/Category combination:
Supplier
| id | name |
|----|------|
| 1 | John |
| 2 | Ana |
| 3 | Dan |
Category
| id | name |
|----|------------|
| 1 | category 1 |
| 2 | category 2 |
| 3 | category 3 |
Supplier_categories
| id | Supplier_id | categ_id |
|----|-------------|----------|
| 1 | 1 | 1 |
| 2 | 1 | 2 |
| 3 | 2 | 2 |
| 4 | 2 | 3 |
Then you can retrieve a list of each supplier categories by doing INNER JOIN to the three tables and putting conditions like this:
SELECT Supplier.id, Category.name
FROM Supplier
INNER JOIN Supplier_categories
on Supplier_categories.Supplier_id = Supplier.id
INNER JOIN Category
ON Category.id = Supplier_categories.categ_id
WHERE Supplier.id = 1 //(for example)

Answer 2

Assuming your tbl_supplier contains a sid primary key, and then that key is present in tbl_categories to keep track of suppliers, and cat is the column to hold category name, the query would be like this:
Select c.cat from tbl_supplier as t, tbl_categories as c where t.sid=c.sid and t.sid='supplier-1'
Example for Supplier 1:
<label>Supplier1:</label>
<select name="supplier-1">
<option>All</option>
<?php
$query = mysqli_query($conn,"Select c.cat from tbl_supplier as t, tbl_categories as c where t.sid=c.sid and t.sid='supplier-1'");
while($row=mysqli_fetch_array($query)){
echo "<option>".$row['cat']."</option>";
}
?>
</select>
However, if you would like to dynamically add multiple suppliers dropdowns then you would need to write a more complex query.
Hope I helped!