Mastering Oracle SQL: Create Synonyms in a Few Easy Steps

Oracle SQL: Synonyms

Table of Contents

1. Introduction to Synonyms
2. Why Synonyms are Required
3. Syntax of Creating Synonyms
4. Practical Example of Creating a Synonym
5. Access and Permissions for Synonyms
6. Performing DML Operations on Synonyms
7. Pros and Cons of Using Synonyms
8. Conclusion
9. Frequently Asked Questions (FAQs)

Introduction to Synonyms

In this article, we will explore the concept of synonyms in Oracle SQL. A synonym is an alternate name for any database object, such as tables, views, procedures, or functions. It allows us to refer to an object by a different name without revealing the original object. This can be useful in scenarios where we want to hide the original object or provide a more user-friendly naming convention.

Why Synonyms are Required

The need for synonyms arises when we want to avoid exposing the original table, view, or procedure names to users. By using synonyms, we can provide a more abstract and intuitive name that better conveys the purpose of the object. Additionally, synonyms can be used to simplify complex queries or provide a level of indirection in accessing data.

Syntax of Creating Synonyms

To create a synonym in Oracle SQL, we use the CREATE SYNONYM statement. The syntax for creating a synonym is as follows:

CREATE [OR REPLACE] [PUBLIC|PRIVATE] SYNONYM synonym_name FOR object_name;

• The OR REPLACE clause allows us to replace an existing synonym with the same name.
• The PUBLIC or PRIVATE keyword determines the visibility of the synonym to other users.
• synonym_name is the name we want to assign to the synonym.
• object_name is the name of the original object for which we are creating the synonym.

Practical Example of Creating a Synonym

Let's consider a practical example to understand how to create a synonym. Suppose we have a table named employees, and we want to create a synonym named emp for this table. We can use the following code to create the synonym:

CREATE OR REPLACE PUBLIC SYNONYM emp FOR employees;

This code creates a public synonym named emp for the employees table. This means that all users within the database can access the emp synonym and perform operations on the underlying employees table.

Access and Permissions for Synonyms

The access and permissions for synonyms depend on whether they are created as public or private. Public synonyms are visible to all users within the database and can be accessed without any additional privileges. On the other hand, private synonyms are only visible to the user who created them and require appropriate privileges to be accessed by other users.

Performing DML Operations on Synonyms

Synonyms in Oracle SQL can be used to perform Data Manipulation Language (DML) operations such as INSERT, UPDATE, DELETE, and SELECT. However, the user performing these operations must have the necessary privileges on the original object.

For example, if we have a synonym named emp for the employees table, we can use the synonym to update the data in the employees table. The following code demonstrates how to update the salary of an employee using the synonym:

UPDATE emp SET salary = salary + 100 WHERE employee_id = 1001;

In this case, the synonym emp allows us to access the data in the employees table without directly referencing it.

Pros and Cons of Using Synonyms

Pros:

• Provides a level of abstraction and security by hiding the original object names
• Simplifies complex queries by using more intuitive names
• Allows for a more user-friendly experience

Cons:

• Increased complexity in managing synonyms, especially in a large database environment
• Can lead to confusion if synonyms are not properly documented and maintained

Conclusion

Synonyms are a powerful feature in Oracle SQL that allow us to create alternate names for database objects. They provide flexibility, security, and simplification when working with database objects. Understanding the syntax and usage of synonyms can greatly enhance the usability and maintainability of an Oracle database.

Frequently Asked Questions (FAQs)

Q: Can I create a private synonym in Oracle SQL? A: Yes, you can create private synonyms that are only visible to the user who creates them.

Q: What happens if I drop a synonym? A: Dropping a synonym does not affect the original object. The data within the original object remains unaffected.

Q: Can I perform DML operations on a synonym? A: Yes, you can perform DML operations on synonyms as long as you have the necessary privileges on the underlying object.

Q: Which users can access a public synonym? A: Public synonyms are visible to all users within the database and can be accessed without any additional privileges.