Synonyms in SQL Server

Synonyms in SQL Server

Introduction
In SQL Server, a synonym is an alias or a nickname for an existing database object, such as a table, view, stored procedure, or another synonym. It provides a way to simplify the process of accessing database objects by providing an alternative name. Synonyms can be particularly useful when you have a complex database schema or when you want to abstract the underlying objects for security or maintainability reasons.

Creating a Synonym
To create a synonym in SQL Server, you can use the CREATE SYNONYM statement. The basic syntax is as follows:

sql
CREATE SYNONYM [schema_name_1.][synonym_name] FOR [schema_name_2.][object_name];

Explanation:

• [schema_name_1.]: The schema in which the synonym will be created. This is optional and is only necessary if you want to specify a specific schema. If not provided, the default schema will be used.
• synonym_name: The name of the synonym you want to create.
• [schema_name_2.]: The schema of the underlying database object (table, view, stored procedure, etc.) for which you want to create the synonym. This is optional and is only necessary if the object is not in the default schema.
• object_name: The name of the underlying database object for which you want to create the synonym.

Example:
Let's assume we have a table called Employees in the schema dbo. We want to create a synonym called Emp for this table:

sql
USE [YourDatabaseName];

CREATE SYNONYM dbo.Emp FOR dbo.Employees;

Using the Synonym
Once the synonym is created, you can use it in your queries as if it were the actual table name. SQL Server will automatically resolve the synonym to the underlying object.

Example:

sql
-- Instead of using the original table name
SELECT * FROM dbo.Employees;

-- You can use the synonym
SELECT * FROM dbo.Emp;

Benefits of Using Synonyms

1. Abstraction: Synonyms provide an abstraction layer, allowing you to change the underlying object's name or location without modifying the queries that use the synonym.
2. Security: Synonyms can be used to grant access to specific objects in different schemas without directly exposing the original object's schema.
3. Simplification: Synonyms can make the code more readable and reduce the need for complex and lengthy identifiers in queries.

Drop a Synonym
To remove a synonym, you can use the DROP SYNONYM statement:

sql
DROP SYNONYM [schema_name.][synonym_name];

Example:

sql
USE [YourDatabaseName];

DROP SYNONYM dbo.Emp;

Conclusion
Synonyms in SQL Server are useful constructs that provide an alias for database objects, simplifying the query writing process and enhancing security and maintainability. They can be a valuable tool in managing complex database schemas and working with multiple schemas in the same database.