能够用于DROP的object_type，如Tables, Database, Function, Trigger, Stored Procedure, Column, User, Type, View, Schema，皆可套用,比如：
ALTER TABLE PERSON DROP COLUMN If EXISTS NAME
SQL Server 2016新特性：DROP IF EXISTS
标签：base sys ges .net sch function name exists 删除
SQL Server 2016新特性：DROP IF EXISTS
DROPobject_type
IFEXISTSobject_name