Question

I have two tables A and B with A referencing a column in B with foreign key constraint. Now, i am trying to add more columns and constraints to table A by dropping table A and creating the table A again with new columns. SQL Server Mgmt Studio provides the “Drop and Create” option to do this where i alter the create table statement to add more columns.

Executing the statements throws an error stating A is referenced by a foreign key constraint. To fix this, i had to removed the foreign key constraint from the table A and then execute “drop and create” the statement. In my case, i could do this by dropping one constraint. I can’t image doing the same with a set of tables cross referencing each other.
This should be a common occurrence for most of the SQL designers and i am wondering if there is a way to manage this situation without deleting and recreating the web of constraints across tables.

Appreciate your comments!

EXAMPLE OF SQL:
Current table:

CREATE TABLE [dbo].[TableA](
    [PhotoId] [bigint] IDENTITY(1,1) NOT NULL,
    [PhotoTypeId] [bigint] NOT NULL,
    [PhotoDescription] [nvarchar](max) NULL,
    [LastModifiedBy] [bigint] NOT NULL,
    [LastModifiedDate] [datetime] NOT NULL,
 CONSTRAINT [PK_TableA] PRIMARY KEY CLUSTERED 
(
    [PhotoId] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

SET ANSI_PADDING OFF
GO

ALTER TABLE [dbo].[TableA]  WITH NOCHECK ADD  CONSTRAINT [FK_TableA_TableAType] FOREIGN KEY([PhotoTypeId])
REFERENCES [dbo].[TableAType] ([PhotoTypeId])
GO

ALTER TABLE [dbo].[TableA] NOCHECK CONSTRAINT [FK_TableA_TableAType]
GO

ALTER TABLE [dbo].[TableA]  WITH NOCHECK ADD  CONSTRAINT [FK_TableA_TableB1] FOREIGN KEY([LastModifiedBy])
REFERENCES [dbo].[TableB] ([UserId])
GO

ALTER TABLE [dbo].[TableA] NOCHECK CONSTRAINT [FK_TableA_TableB1]
GO

ALTER TABLE [dbo].[TableA] ADD  CONSTRAINT [DF_TableA_IsDeleted]  DEFAULT ((0)) FOR [IsDeleted]
GO

expected table

CREATE TABLE [dbo].[TableA](
    [PhotoId] [bigint] IDENTITY(1,1) NOT NULL,
    [PhotoTypeId] [bigint] NOT NULL,
    [PhotoDescription] [nvarchar](max) NULL,
    ***[PhotoWidth] [int] NOT NULL,
    [PhotoHeight] [int] NOT NULL,***
    [LastModifiedBy] [bigint] NOT NULL,
    [LastModifiedDate] [datetime] NOT NULL,
 CONSTRAINT [PK_TableA] PRIMARY KEY CLUSTERED 
(
    [PhotoId] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

SET ANSI_PADDING OFF
GO

ALTER TABLE [dbo].[TableA]  WITH NOCHECK ADD  CONSTRAINT [FK_TableA_TableAType] FOREIGN KEY([PhotoTypeId])
REFERENCES [dbo].[TableAType] ([PhotoTypeId])
GO

ALTER TABLE [dbo].[TableA] NOCHECK CONSTRAINT [FK_TableA_TableAType]
GO

ALTER TABLE [dbo].[TableA]  WITH NOCHECK ADD  CONSTRAINT [FK_TableA_TableB1] FOREIGN KEY([LastModifiedBy])
REFERENCES [dbo].[TableB] ([UserId])
GO

ALTER TABLE [dbo].[TableA] NOCHECK CONSTRAINT [FK_TableA_TableB1]
GO

ALTER TABLE [dbo].[TableA] ADD  CONSTRAINT [DF_TableA_IsDeleted]  DEFAULT ((0)) FOR [IsDeleted]
GO

Answer 1

Solution: Don’t use the table designer in Management Studio. Seriously. Don’t. It’s a relic from more than a decade ago, and it doesn’t know SQL very well. (Check out connect.microsoft.com, and you’ll find many, many bugs and suggestions filed against it.)

You can (and should) add columns and constraints using SQL without dropping and recreating the table, copying data, recreating constraints, etc.

ALTER TABLE A ADD myNewColumn int;
ALTER TABLE A ADD CONSTRAINT ...

If you have a particular situation you don’t know the SQL for, please give the CREATE TABLE/INDEX/CONSTRAINT statements and explain what you need to do.

Added: For the example you added to your question, here’s the one line SQL. I added defaults just because you’ll need them if your table already contains data when you add the columns, which are NOT NULL.

ALTER TABLE dbo.TableA ADD PhotoWidth INT NOT NULL DEFAULT 640, PhotoHeight INT NOT NULL DEFAULT 480;