ALTER TABLE [tb] ALTER COLUMN [name] VARCHAR(1) NULL
alter table #t alter column 字段 char(1) null
你可将后面的VARCHAR(50)改为你原来的类型,主要是重新定义字段类型,去掉NULL而已
--> 测试数据:[tb] IF OBJECT_ID('[tb]') IS NOT NULL DROP TABLE [tb] GO CREATE TABLE [tb]([name] VARCHAR(1) NOT NULL ) GO INSERT [tb] SELECT NULL GO ALTER TABLE [tb] ALTER COLUMN [name] VARCHAR(1) NULL GO INSERT [tb] SELECT NULL GO --------------开始查询--------------------------SELECT * FROM [tb] ----------------结果---------------------------- /* name ---- NULL(1 行受影响)*/
ALTER TABLE [tab] ALTER COLUMN [colname] VARCHAR(10) NULL
IF OBJECT_ID('[tb]') IS NOT NULL DROP TABLE [tb]
GO
CREATE TABLE [tb]([name] VARCHAR(1) NOT NULL )
GO
INSERT [tb] SELECT NULL
GO
ALTER TABLE [tb] ALTER COLUMN [name] VARCHAR(1) NULL
GO
INSERT [tb] SELECT NULL
GO
--------------开始查询--------------------------SELECT * FROM [tb]
----------------结果----------------------------
/*
name
----
NULL(1 行受影响)*/
ALTER TABLE [tab] ALTER COLUMN [colname] VARCHAR(10) NULL