* Mark Riehl > All - We're using MySQL under Linux to capture and analyze > network traffic. We have two tables that store all the messages sent, > and, another table that stores all the messages received. The sent > table has an transmit column (as a double) and the received table has > a received time sent time (from the incoming packet) both stored as > doubles (seconds and fractions of seconds). > In addition, there are a few other fields that distinctly define each > message (e.g., source IP, source port, etc.). > > We're trying to perform some analysis on the data and seem to be having > trouble matching columns of type double. For example, we loop through all > of the received messages and try to find the corresponding message in the > transmit table based on the transmit time (which appears on both tables). > However, when the double transmit time is part of the query, we can't seem > to find matches. Wrapping the transmit time in the select statement with > ROUND() finds the matching records. > > Is it possible that some rounding is taking place here? We've considered > storing time as two separate INT columns (like the timeval > struct), however, we'd prefer to have 1 time column. > > Any suggestions?
Using approximate numbers is tricky, I usually avoid it, and would probably have used a separate column for the fractions in this case, maybe a tinyint, if two digits for the fractions is sufficient. Take a look at this: <URL: http://www.mysql.com/doc/en/Problems_with_float.html > At the end of the page there is an example using ABS(), I guess this is a relatively easy way for you to fix your problem, if you decide to keep your DOUBLE column. -- Roger -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
