Query and Synchronization...

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Hi people!
I was writing a function in which I execute a query to READ some
value, and another one to UPDATE the previous query related data.

query-> select * from ..... to retrieve myvalue
read myvalue
change myvalue
query-> update myvalue

Suddenly I had a doubt...
Can 2 or more browsers call the same function at "same time" and start
the UPDATE query with some still uncomputed data? or is the function
In positive case, should I use some mechanism as Semaphore?
tnx in advance, Giovanni

Re: Query and Synchronization...

Giovanni wrote:
Quoted text here. Click to load it

Well, 'uncomputed data', no... They can overwrite each others changes  
though. Most of my systems aren't that busy, so I opt for:

UPDATE table SET field1=..., field2=... WHERE field1=..., field2=...

If there's no row updated, report the record has been changed, and ask  
the user again...

Rik Wasmus

Estimated date being able to walk again: 01-05-2007.
Less then a week, hurray!

Re: Query and Synchronization...

That's the situation... I've to grant round robin algho in a small
number of records i.e. 20...
The operations are theese:
MYSQL->select id,ticket
PHP-> search ticket=true
MYSQL-> SET ticket=false with id=ID
MYSQL-> SET ticket=true with id=nextticket_at_id();

semaphore could help me?

I was thinking to change strategy...
I wisha use datetime type to retrieve the oldest record not retrieved,
and so update it with NOW()
selecting the record in age order and limiting to 1 i could have what
I want...
dont'you think?

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