Question

I’d like to update a set of rows based on a simple criteria and get the list of PKs that were changed. I thought I could just do something like this but am worried about possible concurrency problems:

SELECT Id FROM Table1 WHERE AlertDate IS NULL; UPDATE Table1 SET AlertDate = getutcdate() WHERE AlertDate IS NULL; 

If that is wrapped in a transaction are there any concurrency issues that can occur? Or is there a better way to do this?

Answer 1

Consider looking at the OUTPUT clause:

USE AdventureWorks2012;   GO    DECLARE @MyTableVar table(       EmpID int NOT NULL,       OldVacationHours int,       NewVacationHours int,       ModifiedDate datetime);    UPDATE TOP (10) HumanResources.Employee   SET VacationHours = VacationHours * 1.25,       ModifiedDate = GETDATE()    OUTPUT inserted.BusinessEntityID,          deleted.VacationHours,          inserted.VacationHours,          inserted.ModifiedDate   INTO @MyTableVar;    --Display the result set of the table variable.   SELECT EmpID, OldVacationHours, NewVacationHours, ModifiedDate   FROM @MyTableVar;   GO   --Display the result set of the table.   SELECT TOP (10) BusinessEntityID, VacationHours, ModifiedDate   FROM HumanResources.Employee;   GO