On Jul 17, 2009, at 11:56 AM, Bastien Koert wrote:
On Fri, Jul 17, 2009 at 11:51 AM, tedd<tedd.sperling@xxxxxxxxx> wrote:
At 11:12 AM -0400 7/17/09, Jason Pruim wrote:
Hi everyone!
So some of you may have noticed that I have been away for quite
awhile...
Been trying to get settled (Moved across the country) and getting
a job.
And now that that is done I have a question about a project that I
might
be doing for my current employer and want to do it properly.
If all goes through, I'll be writing an online database that
upwards of 10
people will be using at various times through out the day.
Basically, in a
form they fill out a model number, customer name, phone number
etc. etc..
And then submit the form. After submitting they need to write the
log number
on some paperwork. If I have 2 people submit the form at the same
time, I'm
thinking I could end up with a race condition and they might get
the wrong
log number (The log number is simply a consecutive record number)
Do I need to be reading up on locking tables/rows? Or in my
situation as
I've briefly described it do I not have to worry about it? Or is
there a
third door with the magic bullet that will solve all my problems? :)
Any advice is greatly appreciated as always, RTFMing is good as
well, as
long as M is defined :)
I'm not afraid of google either, just need the right terms to hit
it with
so I don't go into "search overload" as the commercials for a
rival search
engine claim :)
Thanks Everyone!
Jason:
Welcome back.
Clearly if you have two or more people checkout the same record at
the same
time and each edits the record then you ARE going to have problems
when each
updates the record.
You can solve this problem by using transactions -- here's a link:
http://dev.mysql.com/doc/refman/5.0/en/lock-tables-and-transactions.html
When someone is editing a record, you also need to be able to show
the next
person(s) that the record they want is currently busy and not
available.
However, I'm not sure as to how to notify the next user that the
table is
locked via php. Perhaps a table status might provide that
information. If
so, then use that to notify the next user.
As for your log of activity, just create a another record (with an
auto_increment index) in your activity log table and update that
record with
the data you need to record, such as user id, timestamp, what
record they
accessed and whatever else you want after the transaction is
completed.
Cheers,
tedd
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As a further note to tedd's reply on transactions, you will need to
use the INNODB engine in mysql should you want to use transactions.
Transactions here are done a row locking level not table so you should
have fewer issues.
I also just found out that unless I can convince them to host it off
site, it'll be on a windows machine.... So php & mssql... Does that
change alot?
To answer some of the other questions the Log number is currently just
an auto incrementing consuctive number. So an auto+increment would
work perfectly. What I'm trying to avoid is:
User1
User2
User1 submits to log number 12345
User2 submits to log number 12346
User1 is told their log number is 12346
User2 is told their log number is 12346
But User1 & User2 are on different computers... And if it's as easy as
using the equivelant for: SELECT * FROM table WHERE UserID="User1"
ORDER BY lognumber desc LIMIT 1; Then I'm good... I know how to
proceed with writing it... Just need to figure out how to bill/sell
it! ;)
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