How to get specific attribute from DB

If the data you placed at the beginning of your question is the result of your database query (I’m unsure by how your question is worded), you will want to take that query result and use the PHP function unserialize() to convert that data to an array, then you can access your data from that array.

Your serialized data will become at array that looks like this:

Array
(
    [0] => Array
        (
            [wwsd_percent_discount] => 10
            [wwsd_minimum_discount_qrt] => 20
        )

    [1] => Array
        (
            [wwsd_percent_discount] => 20
            [wwsd_minimum_discount_qrt] => 50
        )

    [2] => Array
        (
            [wwsd_percent_discount] => 30
            [wwsd_minimum_discount_qrt] => 100
        )
)