有没有办法测试 DELETE 是否会因约束而失败？

Question

我希望能够预测 DELETE 是否会违反约束，而无需实际执行删除。

我有什么选择来做这件事？有没有一种简单的方法可以对 DELETE 进行“试运行”？

Answer 1

如果您的目标是仅在所有删除都成功时处理所有删除，为什么不使用 TRY/CATCH：

BEGIN TRANSACTION;
BEGIN TRY
  DELETE #1;
  DELETE #2;
  DELETE #3;
  COMMIT TRANSACTION;
END TRY
BEGIN CATCH
  ROLLBACK TRANSACTION;
END CATCH

如果目标是允许所有成功的删除成功，即使一个或多个失败，那么您可以使用单独的 TRY/CATCH，例如

BEGIN TRY
  DELETE #1;
END TRY
BEGIN CATCH
  PRINT 1;
END CATCH

BEGIN TRY
  DELETE #2;
END TRY
BEGIN CATCH
  PRINT 1;
END CATCH

Answer 2

一种选择是开始事务，运行删除，然后始终回滚：

begin tran

delete Table1 where col1 = 1

-- Test whether it is there
select * from Table1 where col1 = 1

rollback tran

-- Confirm that it is still there
select * from Table1 where col1 = 1