“xxxx”表 - 无法修改表。 不能将值 NULL 插入列 'xxxx'

问题

向已有表增加字段

执行下面sql，sql执行增加两个字段分别：

1. articleTitle 正标题 [nvarchar](200)
2. articleSubTitle 副标题 [nvarchar](200)

USE [tg_thirdparty]
GO

/****** Object:  Table [dbo].[WX_Activity]    Script Date: 10/31/2018 10:54:46 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

SET ANSI_PADDING ON
GO

IF NOT EXISTS ( SELECT  1
                FROM    SYSOBJECTS T1
                        INNER JOIN SYSCOLUMNS T2 ON T1.ID = T2.ID
                WHERE   T1.NAME = 'WX_Activity'
                        AND T2.NAME = 'articleTitle' )
    BEGIN

        ALTER TABLE [dbo].[WX_Activity] ADD [articleTitle] [nvarchar](200) NOT   NULL
        --ALTER TABLE [dbo].[WX_Activity] ADD  CONSTRAINT [DF_WX_Activity_articleTitle]  DEFAULT ('') FOR [articleTitle]
        --ALTER TABLE [dbo].[WX_Activity] ALTER COLUMN [articleTitle] [nvarchar](200) NOT NULL

        EXEC sys.sp_addextendedproperty @name = N'MS_Description',
            @value = N'正标题', @level0type = N'SCHEMA', @level0name = N'dbo',
            @level1type = N'TABLE', @level1name = N'WX_Activity',
            @level2type = N'COLUMN', @level2name = N'articleTitle'

    END

GO

IF NOT EXISTS ( SELECT  1
                FROM    SYSOBJECTS T1
                        INNER JOIN SYSCOLUMNS T2 ON T1.ID = T2.ID
                WHERE   T1.NAME = 'WX_Activity'
                        AND T2.NAME = 'articleSubTitle' )
    BEGIN

        ALTER TABLE [dbo].[WX_Activity] ADD [articleSubTitle] [nvarchar](200) NOT  NULL
        --ALTER TABLE [dbo].[WX_Activity] ADD  CONSTRAINT [DF_WX_Activity_articleSubTitle]  DEFAULT ('') FOR [articleSubTitle]
        --ALTER TABLE [dbo].[WX_Activity] ALTER COLUMN [articleSubTitle] [nvarchar](200) NOT NULL

        EXEC sys.sp_addextendedproperty @name = N'MS_Description',
            @value = N'副标题', @level0type = N'SCHEMA', @level0name = N'dbo',
            @level1type = N'TABLE', @level1name = N'WX_Activity',
            @level2type = N'COLUMN', @level2name = N'articleSubTitle'

    END

GO
    

提示错误

消息 4901，级别 16，状态 1，第 10 行
ALTER TABLE 只允许添加满足下述条件的列: 列可以包含 Null 值；或者列具有指定的 DEFAULT 定义；或者要添加的列是标识列或时间戳列；或者，如果前几个条件均未满足，则表必须为空以允许添加此列。不能将列"articleTitle"添加到非空表"WX_Activity"中，因为它不满足上述条件。
消息 4901，级别 16，状态 1，第 9 行
ALTER TABLE 只允许添加满足下述条件的列: 列可以包含 Null 值；或者列具有指定的 DEFAULT 定义；或者要添加的列是标识列或时间戳列；或者，如果前几个条件均未满足，则表必须为空以允许添加此列。不能将列"articleSubTitle"添加到非空表"WX_Activity"中，因为它不满足上述条件。

解决方法：

表中已经有数据了，不设置默认值，有要求字段不能为NULL，矛盾了！！

所以先指定默认值，插入字段时，加上默认值 DEFAULT ''

USE [tg_thirdparty]
GO

/****** Object:  Table [dbo].[WX_Activity]    Script Date: 10/31/2018 10:54:46 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

SET ANSI_PADDING ON
GO

IF NOT EXISTS ( SELECT  1
                FROM    SYSOBJECTS T1
                        INNER JOIN SYSCOLUMNS T2 ON T1.ID = T2.ID
                WHERE   T1.NAME = 'WX_Activity'
                        AND T2.NAME = 'articleTitle' )
    BEGIN

        ALTER TABLE [dbo].[WX_Activity] ADD [articleTitle] [nvarchar](200) NOT   NULL DEFAULT ''
        --ALTER TABLE [dbo].[WX_Activity] ADD  CONSTRAINT [DF_WX_Activity_articleTitle]  DEFAULT ('') FOR [articleTitle]
        --ALTER TABLE [dbo].[WX_Activity] ALTER COLUMN [articleTitle] [nvarchar](200) NOT NULL

        EXEC sys.sp_addextendedproperty @name = N'MS_Description',
            @value = N'正标题', @level0type = N'SCHEMA', @level0name = N'dbo',
            @level1type = N'TABLE', @level1name = N'WX_Activity',
            @level2type = N'COLUMN', @level2name = N'articleTitle'

    END

GO

IF NOT EXISTS ( SELECT  1
                FROM    SYSOBJECTS T1
                        INNER JOIN SYSCOLUMNS T2 ON T1.ID = T2.ID
                WHERE   T1.NAME = 'WX_Activity'
                        AND T2.NAME = 'articleSubTitle' )
    BEGIN

        ALTER TABLE [dbo].[WX_Activity] ADD [articleSubTitle] [nvarchar](200) NOT  NULL DEFAULT ''
        --ALTER TABLE [dbo].[WX_Activity] ADD  CONSTRAINT [DF_WX_Activity_articleSubTitle]  DEFAULT ('') FOR [articleSubTitle]
        --ALTER TABLE [dbo].[WX_Activity] ALTER COLUMN [articleSubTitle] [nvarchar](200) NOT NULL

        EXEC sys.sp_addextendedproperty @name = N'MS_Description',
            @value = N'副标题', @level0type = N'SCHEMA', @level0name = N'dbo',
            @level1type = N'TABLE', @level1name = N'WX_Activity',
            @level2type = N'COLUMN', @level2name = N'articleSubTitle'

    END

GO