Why SQL query have p, pd etc on Zen Cart but table in SQL no the p or pd?

[explorer1979]

Hi all,

I am new on php/MySQL and now want to learning it to take more control of Zen Cart.

I have one questions not understand.

It is on MySQL table, such as products, inside it haven't the "p", for example products_id, products_model etc.

But general on the php coding, will see like that query

$products_query_raw = "select p.products_id, p.products_model, pd.products_name, p.products_quantity, p.products_type from " . TABLE_PRODUCTS . " p, " . TABLE_PRODUCTS_DESCRIPTION . " pd where p.products_id = pd.products_id and pd.language_id='" . $_SESSION['languages_id'] . "' order by ".$sOrder." ";
$products = $db->Execute($products_query_raw);


Why add the addition p or pd. on the table's column name on the query? What do it doing?

Thank you very much. And anyone can give me a tutorial good for beginner like me?

[kuroi]

It's called an alias and is a short way of talking to mysql about the table without having to type the whole table name each time.

Otherwise we would have to say things like products.products_id = products_description.products_id when using more than one table in a query to tell mysql to which we are referring, which would get a bit tedious.

There's a tutorial on it here.

[explorer1979]

Kurio,

Thank you very much, now understand where the p, po come from by SQL Alias.