CREATE TABLE Persons
(
Id_p int UNIQUE not null,
LastName VARCHAR(255) NOT NULL,
FirstName VARCHAR(255),
Address VARCHAR(255),
CityName VARCHAR(255),
)
ALTER TABLE Persons
ADD UNIQUE(LastName)
GOALTER TABLE Persons
DROP CONSTRAINT LastName
运行ALTER TABLE Persons
DROP CONSTRAINT LastName出现了问题
Msg 3728, Level 16, State 1, Line 1
'LastName' is not a constraint.
Msg 3727, Level 16, State 0, Line 1
Could not drop constraint. See previous errors.
怎么解决啊?
(
Id_p int UNIQUE not null,
LastName VARCHAR(255) NOT NULL,
FirstName VARCHAR(255),
Address VARCHAR(255),
CityName VARCHAR(255),
)
ALTER TABLE Persons
ADD UNIQUE(LastName)
GOALTER TABLE Persons
DROP CONSTRAINT LastName
运行ALTER TABLE Persons
DROP CONSTRAINT LastName出现了问题
Msg 3728, Level 16, State 1, Line 1
'LastName' is not a constraint.
Msg 3727, Level 16, State 0, Line 1
Could not drop constraint. See previous errors.
怎么解决啊?
DROP CONSTRAINT LastName
--加上括号
ALTER TABLE Persons
DROP CONSTRAINT(LastName)
DROP CONSTRAINT(LastName)
(
Id_p int UNIQUE not null,
LastName VARCHAR(255) NOT NULL,
FirstName VARCHAR(255),
Address VARCHAR(255),
CityName VARCHAR(255),
)
ALTER TABLE Persons
ADD CONSTRAINT u_LastName UNIQUE(LastName)
GOALTER TABLE Persons DROP CONSTRAINT u_LastName
ADD UNIQUE(LastName)
GOALTER TABLE Persons
DROP CONSTRAINT LastName
------
问题出在你的UNIQUE约束没有名字,然后系统会默认一个名字。
删除约束,是删除约束的名字而不是字段的名字。
---
ALTER TABLE Persons
ADD constraint UN_LASTNAME UNIQUE(LastName)
GO
alter table p drop UN_LASTNAME
(
Id_p int UNIQUE not null,
LastName VARCHAR(255) NOT NULL,
FirstName VARCHAR(255),
Address VARCHAR(255),
CityName VARCHAR(255),
)
ALTER TABLE Persons
ADD CONSTRAINT UQ_LastName UNIQUE(LastName)
GOALTER TABLE Persons
DROP CONSTRAINT UQ_LastName