Hello everyone,
To begin the 'delivery_options' is saved as the following example:
serialize(array( 9 => "2," ));
So if you execute this simple code you will get what you asked for before.
To be more clear :
a:1 => means that there one array
i:9 => means that there is an integer and the value is 9
s:2 => this means that a string of length 2 and the value in the next row wich is the id carrier
"2," => id_carrier
BUT
in new versions of Prestashop the serialize was replaced by json_encode so will find another expression in your case it will look like
{"9":"2,"}
I hope i was clear.