SQL Commands Request From A Novice

Hello,

I'm running a (phpBB) forum which uses a MYSQL data base - I can access the database via a webpage through my ISP and it lets me run short scripts (through a web interface). I need to do the following (shown in psuedo code below). I would be eternally grateful if someone could translate it into pure SQL commands for me to paste into my SQL quiery input field on the web page I'm using to access my database. (I'm a complete SQL novice)

=====================
/* I need to be sure these commands will do nothing if 'jeff' does not exist in the user table */

/* extract the id value for the user called 'jeff' from the users table */
user = GET id FROM users WHERE username = "jeff"

/* remove all entries from the forums_watch and topics_watch tables that contain Jeff's userID */
REMOVE ALL ENTRIES WHERE userID = user

notify = 0;

/* insert many entries into the topics_watch table, one for each topic that exists in the topic table */
arrayOfTopicIDs = GET ALL id FROM topics
FOR EACH current_Topic IN arrayOfTopicIDs {
INSERT INTO topics_watch
(topic_id, user_id, notify_status)
values (current_Topic, user, notify)
}

/* insert many entries for jeff into the forums_watch table, one entry for each forum that exists in the forum table */
arrayOfForumIDs = GET ALL id FROM forums
FOR each current_Forum in arrayOfTopicIDs {
INSERT INTO forums_watch
(topic_id, user_id, notify_status)
values (current_Forum, user, notify)
}

=====================

I'm going to implement this with php and MYSQL as a mod for my forum application (phpBB) - but I could really do with a way of doing this immediately with pure SQL commands as a quick and dirty one shot paste into the input field of the MYSQL database web interface until I get the php mod going.

Can this be done using only SQL commands without tedious repetition?

Best Regards,

Alan