I'm trying to make an union of selects with a while loop, getting errors - sql

Question

declare #year int
set #year = 2009
while(year <= 2020)
begin
SELECT A.dsformfieldvalue as Instrumento ,
AVG(DATEDIFF(day, B.DTSTARTDATE , C.DTENDDATE)) as TempoMedio ,
'Jul/2009 a Dez/2009' as Periodo
from wfflow_form_field_log A
right join wfflow_execute_task B on A.codflowexecute = B.codflowexecute
right join wfflow_execute_task C on B.codflowexecute = C.codflowexecute
where A.codflow in (326, 439)
and A.codfield = 2498
and B.codtask = 7064
and C.codtask = 7095
and CONVERT(CHAR(4), B.DTSTARTDATE, 120) = #year
and CONVERT(CHAR(4), B.DTSTARTDATE, 100) in ('Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec')
set #year = #year + 1
group by A.dsformfieldvalue
union all
end
Basically what I'm trying to do is drastically reduce the number of repeated code, as I have to union a whole bunch of selects. I'm trying with a while loop but it is not working. Any input?

Answer 1

I think what you're trying to do is this
select *
from wfflow_form_field_log A
right join wfflow_execute_task B on
A.codflowexecute = B.codflowexecute
where year(b.dtstartdate) between 2009 and 2020
and month(b.dtstartdate)>=7
and ... -- other filters

Answer 2

Your SQL is syntactically invalid. The general form of a select1 statement is
select <result-columns>
from <from-clause-including-joins>
where <where-criteria>
group by <group-by-criteria>
having <having-criteria>
order by <order-by-criteria>
The general form of union/union all is
<select-statement>
UNION [ALL]
<select-statement>
...
where each select statement returns the same number of columns and the corresponding columns in each select statement are of the same type or of a type implicitly convertible to the type of the column in the 1st select statement.
You've placed your statement
set #year = #year + 1
so that it is a part of the select statement.
Further you've added a UNION ALL with no select statement following.
Fix those problems and you should be good. But...as another answer pointed out, what you're really trying to do is select a range of years. You don't need a union: you just need suitable grouping.
If it was my query, I'd do something like this (if I'm understanding your intent correctly):
declare #dtFrom datetime = '2009-01-01 00:00:00.000' -- start of period
declare #dtThru datetime = '2020-12-31 23:59:59.996' -- end of period
select year = datepart(year,b.dtstartdate) ,
period = case datepart(month,b.dtstartdate) / 6 when 1 then 'Jan-Jun' else 'Jul-Dec' end ,
instrumento = a.dsformfieldvalue ,
tempomento = avg( datediff(day, b.dtstartdate , c.dtenddate ) )
from wfflow_form_field_log a
right join wfflow_execute_task b on A.codflowexecute = B.codflowexecute
and B.codtask = 7064
and b.dtStartDate between #dtFrom and #dtThru
right join wfflow_execute_task d on B.codflowexecute = C.codflowexecute
and C.codtask = 7095
where A.codflow in (326, 439)
and A.codfield = 2498
group by datepart(year,b.dtStartDate) ,
case datepart(month,b.dtstartdate) / 6 when 1 then 'Jan-Jun' else 'Jul-Dec' end ,
A.dsformfieldvalue
order by 1,2,3 -- order by the first 3 columns (the grouping columns)
Easy!