A small cheat sheet  of wp’s database functions.

In your own functions put this line of code to be able to use wp’s db:

global $wpdb;

Get a field

$field = $wpdb->get_var($sql);

Get a single row

$row = $wpdb->get_row($sql);

Get some rows

$rows = $wpdb->get_results($sql);

Escape an input

$value = $wpdb->get_escape($input);

Perform a query

$n = $wpdb->query($sql);

WP Tables’ name

You can use

• $wpdb->links
• $wpdb->posts
• …
• and even $wpdb->prefix !

$mylink = $wpdb->get_row("SELECT * FROM $wpdb->links WHERE link_id = 10", ARRAY_N);

Return format

In get_row and get_results you can specify in the second argument the format

• OBJECT – result will be output as an object.
• ARRAY_A – result will be output as an associative array.
• ARRAY_N – result will be output as a numerically indexed array.

More info

Function Reference/wpdb Class « WordPress Codex.

$mylink = $wpdb->get_row("SELECT * FROM $wpdb->links WHERE link_id = 10", ARRAY_N);