Jasmin,
Thursday, May 02, 2002, 5:00:14 PM, you wrote:
JB> I have been trying to use 'user variables' to keep
JB> track of the previous row for use in a calculation of
JB> the present row. Is there a way I can do this? Or
JB> is there a better way in trying to use a previous
JB> rows value in the present row.
JB> For example;
JB> SELECT number as current_day, (number - <prevnumber>)
JB> as change_from_prev_day FROM TABLE ORDER BY DATE
JB> <prevnumber> is the reference that I need from the
JB> previous row.
JB> Am I missing something simple or do I have to do this
JB> outside of MYSQL?
You can do something like that:
SELECT @a:=0;
SELECT (number-@a) AS change_from_prev_day, @a:=number FROM your_table;
Note: you should set value to variable _after_ calculation.
You can find more info about user variables at:
http://www.mysql.com/doc/V/a/Variables.html
http://www.mysql.com/doc/e/x/example-user-variables.html
JB> Any help would be appreciated. thanks, jasmin.
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