Can I use a variable inside cursor declaration? - sql-server

Question

Is this code valid?
-- Zadavatel Login ID
DECLARE #ZadavatelLoginId nvarchar(max) =
(SELECT TOP 1 LoginId
FROM
(SELECT Z.LoginId, z.Prijmeni, k.spojeni
FROM TabCisZam Z
LEFT JOIN TabKontakty K ON Z.ID = K.IDCisZam
WHERE druh IN (6,10)) t1
LEFT JOIN
(SELECT ko.Prijmeni, k.spojeni, ko.Cislo
FROM TabCisKOs KO
LEFT JOIN TabKontakty K ON K.IDCisKOs = KO.id
WHERE druh IN (6, 10)) t2 ON t1.spojeni = t2.spojeni
AND t1.Prijmeni = t2.Prijmeni
WHERE
t2.Cislo = (SELECT CisloKontOsoba
FROM TabKontaktJednani
WHERE id = #IdKJ))
-- Pokud je řešitelský tým prázdný
IF NOT EXISTS (SELECT * FROM TabKJUcastZam WHERE IDKJ = #IdKJ)
BEGIN
DECLARE ac_loginy CURSOR FAST_FORWARD LOCAL FOR
-- Zadavatel
SELECT #ZadavatelLoginId
END
ELSE BEGIN
I am trying to pass the variable #ZadavatelLoginId into the cursor declaration and SSMS keeps telling me there is a problem with the code even though it is working.
Msg 116, Level 16, State 1, Procedure et_TabKontaktJednani_ANAFRA_Tis_Notifikace, Line 575 [Batch Start Line 7]
Only one expression can be specified in the select list when the subquery is not introduced with EXISTS
Can anyone help?

Answer 1

I do not see anything in your posted query that could trigger the specific message that you listed. You might get an error if the subquery (SELECT CisloKontOsoba FROM TabKontaktJednani WHERE id = #IdKJ) returned more than one value, but that error would be a very specific "Subquery returned more than 1 value...".
However, as written, your cursor query is a single select of a scalar, which would never yield anything other than a single row.
If you need to iterate over multiple user IDs, but wish to separate your selection query from your cursor definition, what you likely need is a table variable than can hold multiple user IDs instead of a scalar variable.
Something like:
DECLARE #ZadavatelLoginIds TABLE (LoginId nvarchar(max))
INSERT #ZadavatelLoginIds
SELECT t1.LoginId
FROM ...
DECLARE ac_loginy CURSOR FAST_FORWARD LOCAL FOR
SELECT LoginId
FROM #ZadavatelLoginIds
OPEN ac_loginy
DECLARE #LoginId nvarchar(max)
FETCH NEXT FROM ac_loginy INTO #LoginId
WHILE ##FETCH_STATUS = 0
BEGIN
... Send email to #LoginId ...
FETCH NEXT FROM ac_loginy INTO #LoginId
END
CLOSE ac_loginy
DEALLOCATE ac_loginy
A #Temp table can also be used in place of the table variable with the same results, but the table variable is often more convenient to use.
As others have mentioned, I believe that your login selection query is overly complex. Although this was not the focus of your question, I still suggest that you attempt to simplify it.
An alternative might be something like:
SELECT Z.LoginId
FROM TabKontaktJednani KJ
JOIN TabCisKOs KO ON KO.Cislo = KJ.CisloKontOsoba
JOIN TabCisZam Z ON Z.Prijmeni = KO.Prijmeni
JOIN TabKontakty K ON K.IDCisZam = Z.ID
WHERE KJ.id = #IdKJ
AND K.druh IN (6,10)
The above is my attempt to rewrite your posted query after tracing the relationships. I did not see any LEFT JOINS that were not superseded by other conditions that forced them into effectively being inner joins, so the above uses inner joins for everything. I have assumed that the druh column is in the TabKontakty table. Otherwise I see no need for that table. I do not guarantee that my re-interpretation is correct though.

Answer 2

How about you create a #temp table for each sub query since the problem is coming up due to the sub queries?
CREATE TABLE #TEMP1
(
LoginID nvarchar(max)
)
CREATE TABLE #TEMP2
(
ko.Prijmeni nvarchar(max),
k.spojeni nvarchar(max),
ko.Cislo nvarchar(max)
)