有没有办法同时选择和更新行？

Question

我想根据一个简单的标准更新一组行，并获取已更改的PK列表。我以为我可以做这样的事情，但担心可能出现的并发问题：

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

如果将其包装在事务中，是否会发生任何并发问题？还是有更好的方法来做到这一点？

Answer 1

考虑查看OUTPUT子句：

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