l i n u x - u s e r s - g r o u p - o f - d a v i s
L U G O D
 
Next Meeting:
July 21: Defensive computing: Information security for individuals
Next Installfest:
TBD
Latest News:
Jul. 4: July, August and September: Security, Photography and Programming for Kids
Page last updated:
2004 Mar 31 22:55

The following is an archive of a post made to our 'vox-tech mailing list' by one of its subscribers.

Report this post as spam:

(Enter your email address)
[vox-tech] SQL question (mysql)
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[vox-tech] SQL question (mysql)



Hello,

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

HOWEVER!
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,

Dylan

_______________________________________________
vox-tech mailing list
vox-tech@lists.lugod.org
http://lists.lugod.org/mailman/listinfo/vox-tech



LinkedIn
LUGOD Group on LinkedIn
Sign up for LUGOD event announcements
Your email address:
facebook
LUGOD Group on Facebook
'Like' LUGOD on Facebook:

Hosting provided by:
Sunset Systems
Sunset Systems offers preconfigured Linux systems, remote system administration and custom software development.

LUGOD: Linux Users' Group of Davis
PO Box 2082, Davis, CA 95617
Contact Us

LUGOD is a 501(c)7 non-profit organization
based in Davis, California
and serving the Sacramento area.
"Linux" is a trademark of Linus Torvalds.

Sponsored in part by:
Sunset Systems
Who graciously hosts our website & mailing lists!