Increment a variable with the previous ones

Question

I try to show a curve with energy produced for a day. So the curve must always be growing.

I try to increment the variable "energie_journ" my mysql database with all previous.

Exemple:

Mysql:

ID           energie_journ
1                 5
2                 5
3                 10
4                 6

Desired result:

First energie_journ = 1, the second = 10 (5 +5), third = 20 (5 +5 +10), fourth = 26 (5 +5 +10 +6).

Bit php:

while   ($row2  =   mysql_fetch_array($result2)) {
    extract($row2);

    $datetime *= 1000;

    $encode_energie_journ[] = array((float)$datetime, (float)$energie_journ == null ? null : (float)$energie_journ);
}

Thanks.

You should be adding each row value to an accumulator variable. — alexis
– alexis, Commented Jun 12, 2013 at 19:33

M Khalid Junaid · Accepted Answer · 2013-06-12 19:39:02Z

1

here you go i have made the sum of previous values in the query

SELECT id,(SELECT SUM(energie_journ) FROM `table` WHERE `id` <= p.`id`) AS  sum_col FROM `table` p

just use the result of sum_col which i thinks is as per your needs

hope this makes sense

answered Jun 12, 2013 at 19:39

M Khalid Junaid

64.6k10 gold badges93 silver badges120 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

TGO Over a year ago

Thanks ! I use your method, this is faster !

alexis · Accepted Answer · 2013-06-12 19:36:07Z

1

Try it like this:

$energy_journ = 0;
while   ($row = mysql_fetch_array($result2)) {
    $energy_journ += $row[1];
    // now save this value to an array, if that's what you are after.
}

And avoid using extract, it's going to give you headaches.

answered Jun 12, 2013 at 19:36

alexis

50.4k18 gold badges108 silver badges173 bronze badges

Comments

Ed Gibbs · Accepted Answer · 2013-06-12 19:41:10Z

1

You can also have MySQL calculate this for you:

SELECT
  ID,
  energie_journ,
  @subtot := @subtot + val AS energie_journ_to_date
FROM myTable, (SELECT @subtot := 0) subtots
ORDER BY ID;

The result will look like this:

ID      energie_journ   energie_journ_to_date
 1             5                  5
 2             5                 10
 3            10                 20
 4             6                 26

answered Jun 12, 2013 at 19:41

Ed Gibbs

26.4k4 gold badges50 silver badges75 bronze badges

Collectives™ on Stack Overflow

Increment a variable with the previous ones

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related