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[vox-tech] SQL question (mysql)
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[vox-tech] SQL question (mysql)


I am having a problem getting a query to work with MySQL 3.23.49

I have 3 tables, all which share a common key (user_id):

1. volunteer_info (contains contact information) [key = user_id]
2. assignment_data (contains event assignment information) [key = user_id]
fields include: user_id, event_id
each record represents one event that any one volunteer is assigned to

3. score_board (contains event participation information) [key = user_id]
fields include: user_id, event_id, participation_status
each record represents whether or not a person attended an event

there is a 1:1 relationship between each table, after a few 'where'
statements are applied.

As it stands right now i can access every person who was assigned to a given
event (denoted by the variable $event_id) with the following query:

select volunteer_info.*
       from assignment_data, volunteer_info
       where volunteer_info.user_id = assignment_data.user_id
       and assignment_data.event_id = $event_id

i am able to access the contact info and participation info with this query:

select volunteer_info.*, participation_status
       from assignment_data, volunteer_info, score_board
       where volunteer_info.user_id = assignment_data.user_id
       and volunteer_info.user_id = score_board.user_id
       and assignment_data.event_id = $event_id
       and score_board.event_id = $event_id

The score_board table may or may not contain records that match the second
query, which causes an empty set to be returned - or worse yet - only some
of the records that i am interested in. I have experimented with a left
join, but am not quite sure how to accomplish this.

any ideas?

thanks in advance,


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