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POresolving foreign constraints among connected tables
 

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  1. POresolving foreign constraints among connected tables
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    <p>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.</p> <p>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.</p> <p>Appreciate your comments!</p> <p>EXAMPLE OF SQL: <strong><em>Current table:</em></strong></p> <pre><code>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 </code></pre> <p><strong><em>expected table</em></strong></p> <pre><code>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 </code></pre>
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