How and why should I use SQL Server 2005 synonyms?

By: Jeremy Kadlec | Read Comments | Print Jeremy is the CTO @ Edgewood Solutions, co-founder of MSSQLTips.com and SQL Server MVP since 2009. Related Tips: More

Problem
Changing the name of an table once an application has been deployed has traditionally been a difficult task in SQL Server 2000.  The typical solution in SQL Server 2000 for referencing a different object was to use a View.  A second option was to use the sp_rename system stored procedure to rename objects as needed.  Unfortunately, this limits the capabilities of referencing other objects.  The need to be able to reference another object can become critical during system migrations, application testing, data corruption, etc.  Does SQL Server 2005 handle this in a more elegant manner and support more than just tables? 

Solution
SQL Server 2005 has introduced synonyms which enables the reference of another object (View, Table, Stored Procedure or Function) potentially on a different server, database or schema in your environment.  In short, this means that the original object that is referenced in all of your code is really using a completely different underlying object, but no coding changes are necessary.  Think of this as an alias as a means to simplify migrations and application testing without the need to make any dependent coding changes.

How do I create a synonym via SQL Server 2005 Management Studio?

How do I create a synonym via T-SQL?

USE [UserDefinedDatabase]
GO
CREATE SYNONYM [dbo].[Customer]
FOR [JTKNotebook].[JTKTest].[dbo].[Customer]
GO
EXEC sys.sp_addextendedproperty @name=N'Description', @value=N'This is a sample synonym referencing the JTKTest database' , @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'SYNONYM',@level1name=N'Customer'

How can I verify the statements issued against the synonym are affecting the base object?

Issue an INSERT statement against the synonym:

INSERT INTO [BaltSSUG].[dbo].[Customer]
([CustID] ,[CustName] ,[CustAddress] ,[CustCity] ,[CustState] ,[CustZipCode])
VALUES (99 ,'DBA Dave' ,'123 Main Street' ,'Warren' ,'OH' ,12345)

Issue a SELECT statement on the synonym:

SELECT *
FROM [BaltSSUG].[dbo].[Customer]

1 AAA 123 Main Washington DC 11111
2 BBB 456 Main New York NY 22222
3 CCC 789 Main St. Louis MO 33333
4 DDD 123 Maple Denver CO 44444
5 EEE 456 Maple San Fran CA 55555
99 DBA Dave 123 Main Street Warren OH 12345

Can I still issue statements against the base object?

Issue an INSERT statement against the base table:

INSERT INTO [JTKTest].[dbo].[Customer]
([CustID] ,[CustName] ,[CustAddress] ,[CustCity] ,[CustState] ,[CustZipCode])
VALUES (100 ,'Developer Donna' ,'456 Main Street' ,'Chicago' ,'IL' ,67890)

Issue a SELECT statement on the base table:

SELECT *
FROM [JTKTest].[dbo].[Customer]

1 AAA 123 Main Washington DC 11111
2 BBB 456 Main New York NY 22222
3 CCC 789 Main St. Louis MO 33333
4 DDD 123 Maple Denver CO 44444
5 EEE 456 Maple San Fran CA 55555
99 DBA Dave 123 Main Street Warren OH 12345
100 Developer Donna 456 Main Street Chicago IL 67890

Next Steps

• As you begin to migrate to SQL Server 2005 consider synonyms as a means to alias objects in your environment without the need to change the dependent code.
• The next time you need to make significant code changes due to application testing or a system migration and you are concerned about the level of effort to support the changes, first test the synonym functionality to determine if this will streamline the process and save time.
• Do not limit yourself to uses for the synonyms, consider other applications such as in data warehousing when managing fact tables.
• Check out our recent testing related tips:
  • Testing Options with SQL Server 2000 and 2005
  • How and why would I use multiple instances of SQL Server
  • SQL Server Comparison Tools

Related Tips: More | Become a paid author

Last Update: 9/18/2006

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