This Oracle tutorial explains how to create and drop synonyms in Oracle with syntax and examples.
A synonym is an alternative name for objects such as tables, views, sequences, stored procedures, and other database objects.
You generally use synonyms when you are granting access to an object from another schema and you don't want the users to have to worry about knowing which schema owns the object.
Create Synonym (or Replace)
You may wish to create a synonym so that users do not have to prefix the table name with the schema name when using the table in a query.
The syntax to create a synonym in Oracle is:
CREATE [OR REPLACE] [PUBLIC] SYNONYM [schema .] synonym_name
FOR [schema .] object_name [@ dblink];
- OR REPLACE
- Allows you to recreate the synonym (if it already exists) without having to issue a DROP synonym command.
- It means that the synonym is a public synonym and is accessible to all users. Remember though that the user must first have the appropriate privileges to the object to use the synonym.
- The appropriate schema. If this phrase is omitted, Oracle assumes that you are referring to your own schema.
- The name of the object for which you are creating the synonym. It can be one of the following:
- stored procedure
- materialized view
- java class schema object
- user-defined object
Let's look at an example of how to create a synonym in Oracle.
CREATE PUBLIC SYNONYM suppliers
This first CREATE SYNONYM example demonstrates how to create a synonym called suppliers. Now, users of other schemas can reference the table called suppliers without having to prefix the table name with the schema named app. For example:
If this synonym already existed and you wanted to redefine it, you could always use the OR REPLACE phrase as follows:
CREATE OR REPLACE PUBLIC SYNONYM suppliers
Once a synonym has been created in Oracle, you might at some point need to drop the synonym.
The syntax to drop a synonym in Oracle is:
DROP [PUBLIC] SYNONYM [schema .] synonym_name [force];
- Allows you to drop a public synonym. If you have specified PUBLIC, then you don't specify a schema.
- It will force Oracle to drop the synonym even if it has dependencies. It is probably not a good idea to use force as it can cause invalidation of Oracle objects.
Let's look at an example of how to drop a synonym in Oracle.
DROP PUBLIC SYNONYM suppliers;
This DROP statement would drop the synonym called suppliers that we defined earlier.