mysql - updating a table setting a column with a complex condition - mysql

Question

I have been working on this for a while now and this seems to be too complex. What I want to do is to update a column (x) with the operation: (p * (100/c) ) / 100.
p corresponds to a value of a date x and c corresponds to a value of date x minus one day.
I tried to create a stored procedure with loop but select statement doesnt work for me in the loop statement.
Here is my procedure which update nothing :
BEGIN
DECLARE firstqDate,date2 date;
DECLARE p, c float;
DECLARE cpt, val int;
SET #val = 0;
SET #cpt = (select count(*)-1 from quotes);
WHILE (val < 3) DO
SET #firstqDate = (select qDate from quotes ORDER BY YEAR(qDate) ASC, MONTH(qDate) ASC, DAY(qDate) ASC limit 1,1);
SET date2 = (select qDate from quotes where qDate like DATE_ADD(#firstqDate, INTERVAL 1 DAY );
SET p = (select qOp from quotes where qDate like date2);
SET c = (select qCl from quotes where qDate like DATE_SUB(date2, INTERVAL val DAY));
update quotes
set qCh = (p * (100/c) ) / 100;
set val = val + 1;
end while;
END
EDIT : I did some updates to the stored procedure but still updating no lines!
BEGIN
DECLARE firstqDate,date2 date;
DECLARE p, c float;
DECLARE cpt, val int;
SET #val = 0;
SET #cpt = (select count(*)-1 from quotes);
SET firstqDate = (select qDate from quotes ORDER BY YEAR(qDate) ASC, MONTH(qDate) ASC, DAY(qDate) ASC limit 1,1);
WHILE (val < 3) DO
SET date2 = (select qDate from quotes where qDate like DATE_ADD(#firstqDate, INTERVAL val DAY ));
SET p = (select qOp from quotes where qDate like date2);
SET c = (select qCl from quotes where qDate like DATE_SUB(date2, INTERVAL val+1 DAY));
set val = val + 1;
update quotes
set qCh = (p * (100/c) ) / 100
where qOp = p AND qCl = c;
end while;
END
I did some updates again to the stored procedures but no changes. i used some functions.
BEGIN
DECLARE p, c float;
DECLARE cpt, val int;
SET #val = 0;
SET #cpt = (select count(*)-1 from quotes);
WHILE (#val < 3) DO
SET p = getp(#val, getd());
SET c = getc(#val+1, getd());
set #val = #val + 1;
update quotes
set qCh = (#p * (100/#c) ) / 100
where qOp = #p AND qCl = #c;
end while;
END
functions :
get p:
BEGIN
declare d date;
select qDate into d from quotes ORDER BY YEAR(qDate) ASC, MONTH(qDate) ASC, DAY(qDate) ASC limit 1,1;
return d;
END
get c:
BEGIN
DECLARE c float;
DECLARE qDa date;
select qDate into qDa from quotes where qDate like DATE_SUB(qD, INTERVAL v DAY );
SELECT qCl INTO c FROM quotes WHERE qDate = qDa;
RETURN c;
END
getd:
BEGIN
declare d date;
select qDate into d from quotes ORDER BY YEAR(qDate) ASC, MONTH(qDate) ASC, DAY(qDate) ASC limit 1,1;
return d;
END
this stored procedure must calculate all qCh from p of qDate and c of the qDate minus one day.
Thank you!
EDIT - Solved
Ouf! I finally managed to write this stored procedure :
BEGIN
DECLARE p, c float;
DECLARE cpt, val int;
SET #val = 0;
SET #cpt = (select count(*)-1 from quotes);
WHILE (#val <= 2) DO
SET p := getp(#val, getd());
SET c := getc(#val+1, getd());
set #val := #val + 1;
update quotes q
set q.qCh = (getp(#val, getd()) * (100/getc(#val-1, getd())) ) / 100
where q.qOp = getp(#val, getd());
end while;
END
new getC
BEGIN
DECLARE c float;
DECLARE qDa date;
select qDate into qDa from quotes where qDate like DATE_ADD(qD, INTERVAL v DAY );
SELECT qCl INTO c FROM quotes WHERE qDate = qDa;
RETURN c;
END
I changed the code of function getC to add (-1) in the first iteration. now it is working!
Thank you everyone for your help!

Answer 1

Your update cycle looks ok, even if i don't understand why you make 3 cycles. Shouldn't you use:
WHILE (#val < 3) DO
Instead of
WHILE (val < 3) DO
? Hope it helps
EDIT:
You need to debug your cycle to know where the problem is.
Try this:
BEGIN
DECLARE #p, #c float;
DECLARE #cpt, #val int;
SET #val = 0;
SET #cpt = (select count(*)-1 from quotes);
SELECT 'Enter Cycle';
WHILE (#val < 3) DO
SELECT 'In Cyle';
SET #p = getp(#val, getd());
SELECT #p;
SET c = getc(#val+1, getd());
set #val = #val + 1;
update quotes
set qCh = (#p * (100/#c) ) / 100
where qOp = #p AND qCl = #c;
end while;
END
Does you SP prints 'Enter Cycle' and 'In Cyle'? Does the value of p Variable prints? It is correct?