Update subquery returned more than 1 value.

update targets set [Month] = datepart(month, IssueDate) from issues inner join targets on issues.IssueId = Targets.IssueId

-- SELECT Statement to find unmatched issueids
select oi.orderitemid, oi.issueid, i.issueid, oi.Year, oi.Month, oi.ProductId 
from orderitems oi
inner join issues i on 
	oi.OrderDate = i.IssueDate and
	i.ProductId = oi.ProductId
where oi.Year = 2026 and 
	oi.Deleted = 0 and 
	oi.issueid <> i.issueid

-- SQL to fix it
UPDATE oi
SET oi.issueid = i.issueid
FROM orderitems oi
INNER JOIN issues i
    ON oi.OrderDate = i.IssueDate
   AND oi.ProductId = i.ProductId
WHERE oi.Year = 2026
  AND oi.Deleted = 0
  AND oi.issueid <> i.issueid;