From: Simon J Mudd
Date: March 17 1999 8:58am
Subject: beeing informed of changes in rows in a table (real-time prices)
List-Archive: http://lists.mysql.com/mysql/389
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I'm not very familiar with SQL, but think this is a common problem with
databases treating "real-time data".

I have an application which is being updated with prices from the
financial markets.

I'd like the client application which retrieves this data from the
database not to have to do repeated SELECTs to determine when the data
changes, but to somehow have a way to be advised that a table has
changed.

I think triggers can be used to perform calculations/functions on the data
in the database (as inserts/updates take place) which would solve most of
my problems, but I still need the "client" to know when the data changes.  
If I want to cope with "real-time" (sub 1 second) updates for a number of
clients frequent SELECTS will presumably cause a severe load on the
server, which I'd prefer to avoid.

For the time being I can afford to "poll" every 10-30 seconds.

How is this problem solved in other "big" databases, and are there
facilities for doing this in MySQL?  (Presumably this isn't standard SQL)

I'm running

Server version          3.22.16a-gamma
Protocol version        10
Connection              mysql via TCP/IP
TCP port                3306
Uptime:                 4 days 16 hours 38 min 0 sec

on Solaris 2.6 with clients using ODBC running Visual Basic :-(

Thanks for any pointers on the subject.

regards,

Simon

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