问题
I'm trying to drop a constraint on a DB table, something like:
ALTER TABLE MyTable drop CONSTRAINT FK_MyTable_AnotherTable
But the execution just runs and runs. If I stop it I see:
Msg 3727, Level 16, State 0, Line 2
Could not drop constraint. See previous errors.
Web search throws up various pages but note that the constraint is properly named and I am trying to remove it using the correct name
回答1:
I was having the same issue on SQL Server 2008 R2, I solved my problem with below line hopefully it will work for someone else as well :)
Alter Table [Table Name]
DROP Column [Column Name]
回答2:
Found a way to sort this, although I don't understand why it was necessary.
Have been able to drop the constraint by disabling it first:
ALTER MyTable NOCHECK CONSTRAINT FK_MyTable_AnotherTable
The drop then completes fine
Would still welcome any comments on the reason why this is necessary
回答3:
Verify that you've not already dropped the constraint, like:
SELECT OBJECT_ID('FK_MyTable_AnotherTable')
If this returns null, your constraint no longer exists. That would explain the error message.
回答4:
I had same problem.
The reason was that I made a mistake in my cursor statement, which was iterating some constraint I was to drop. So this error occurred when the constraint was actually removed in the same transaction. Then I did a rollback and checked if it existed: it did (of course, after rollback!).
Check if it really exists at the moment of dropping.
来源：https://stackoverflow.com/questions/2592977/unable-to-drop-constraint-in-sql-server-2005-could-not-drop-constraint-see-pr