How to do a proper SQL recursion? - mysql

Question

I'm currently working on a little error-handling issue in the following query:
declare #DayCounter int
declare #rows int
set #DayCounter = -2
set #rows = 0
while #rows = 0
begin
select
coalesce(p.name, case when len(ol.action)>1 then substring(ol.action,1,40)+'<br />'+substring(ol.action,41,80) else ca.code end) as description
, convert(varchar,DateAdd(minute,
15 * ((60 * Datepart(hour, latest_payment_status_change) +
Datepart(Minute, latest_payment_status_change)+
Case When DatePart(second, latest_payment_status_change) < 30
Then 7 Else 8 End) / 15),
DateAdd(day, DateDiff(day, 0, latest_payment_status_change), 0)),126) as date_time
, sum(num_of_persons) as num_tickets
from tick_order o
join tick_orderline ol on ol.order_id=o.id
join (
select olt.id
from tick_orderline_type olt
join tick_case ca on ca.id=olt.case_id
join tick_client tcl on tcl.id = ca.client_id
where tcl.id = 'CLIENT_TEST'
union
select orderline_type_id
from rpt_client_orderline_type rcot
join tick_client tcl on tcl.id = rcot.client_id
where tcl.id = 'CLIENT_TEST'
union
select olt.id
from tick_orderline_type olt
join rpt_client_case rcc on rcc.case_id=olt.case_id
join tick_client cl on cl.id=rcc.client_id
where cl.id = 'CLIENT_TEST'
) olt2 on olt2.id=ol.orderline_type_id
join tick_orderline_type olt on olt.id=ol.orderline_type_id
join tick_case ca on ca.id=olt.case_id
join tick_client cl on cl.id=ca.client_id
join tick_user_case uc on uc.case_id=ca.id
join tick_user u on u.id=uc.user_id
left join tick_promotion_code pc on pc.id=o.promotion_code_id
left join tick_promotion p on p.id=pc.promotion_id
where o.latest_payment_status_change>=dateadd(day,#DayCounter,current_timestamp)
and ((o.latest_payment_status_code = 'ORDER_PAYMENT_OK')
or (o.latest_payment_status_change > dateadd(minute,30,current_timestamp)
and o.latest_payment_status_code = 'ORDER_PAYMENT_WAITING' ))
group by
coalesce(p.name, case when len(ol.action)>1 then substring(ol.action,1,40)+'<br />'+substring(ol.action,41,80) else ca.code end)
, convert(varchar,DateAdd(minute,
15 * ((60 * Datepart(hour, latest_payment_status_change) +
Datepart(Minute, latest_payment_status_change)+
Case When DatePart(second, latest_payment_status_change) < 30
Then 7 Else 8 End) / 15),
DateAdd(day, DateDiff(day, 0, latest_payment_status_change), 0)),126)
order by 1,2
set #DayCounter = #DayCounter - 1;
if ##rowcount <> 0
begin
set #rows = ##rowcount;
print #DayCounter;
end;
end;
The data retrieved is used for a diagram that shows sales per sale-type from the past two days. What I'm trying to achieve now is: When no sales have been made in the past two days (##rowcount = 0), check back a day further each time until data has been found.
The query as it stands now returns something like this (I tried getting the image working, but I somehow am unable to; have a link instead):
https://www.dropbox.com/s/0hculuegrc88c69/SQL_Result.png?dl=0
And it doesn't stop, because for some reason the #rows variable stays 0, despite the query clearly returning rows. Even when using print ##rowcount it returns rows.
SO how do I fix this? Should I use a completely different method?
-Zubaja

Answer 1

It would seem I did not quite understood what my employer meant. He didn't want the error-handling in the SQL, but rather on the website: When no data is found for the past two days, simply show an empty diagram.