ID Number: Q64559
1.00 1.10 1.11 4.20
OS/2
Summary:
MIN and MAX should not be used on timestamp columns to number rows
because MIN and MAX incorrectly assume the rightmost byte is the most
significant byte. Timestamps are actually incremented by assuming that
the rightmost byte is the least significant byte.
After 255 updates, MIN and MAX assume the value has changed from the
most positive value to the most negative value when the value really
only increased by one. If a technique such as the following is used to
number rows, all the rows with timestamps greater than the old
timestamp of the row that crossed the 255 boundary will be skipped:
select @current="",@n=0
select @cnt=count(*) from t1
while @n<@cnt begin
select @n=@n+1
select @current=min(timestamp) from t1 where key>@current
update t1 set rowcnt=@n where key=@current
Additional reference words: 1.00 1.10 1.11 4.20