How to query synonyms in oracle

Synonyms in Oracle are a very useful feature that allows users to use simple aliases to access other tables or views. Synonyms allow developers to easily access another user's table or view without knowing its full name or location. In addition, using synonyms can hide underlying implementation details, thus simplifying code and improving maintainability.

But when we need to query synonyms, how should we do it?

First, we need to know how to create synonyms in Oracle. The syntax for creating synonyms is as follows:

CREATE [PUBLIC] SYNONYM synonym_name FOR [schema.]object_name [@db_link];

Among them, synonym_name is the name of the synonym, schema is the schema where the base object is located, object_name is the name of the base object, and db_link is the database that needs to be connected if you want to reference cross-database objects.

Next, let’s take a look at how to query synonyms in Oracle. There are many ways to query synonyms. The following are two common query methods:

Method 1: Use the DESCRIBE command

In Oracle, we can use the DESCRIBE command to query a certain synonym The structural information of the corresponding base table. For example, we created the following synonym:

CREATE SYNONYM emp FOR hr.employees;

Then, we can use the DESCRIBE command to query the structural information of the base table hr.employees corresponding to the synonym emp. The specific operations are as follows:

DESCRIBE emp;

After executing this command, Oracle will return a descriptive list containing base table structure information.

Method 2: Use the SELECT command to query synonyms

In addition to using the DESCRIBE command, we can also use the SELECT command to query the information of the base table corresponding to the synonym. The specific operations are as follows:

SELECT * FROM emp;

After executing this command, Oracle will return the information of the base table corresponding to the synonym.

Of course, if we want to query the definition information of synonyms, we can also use the following SQL statement to query:

SELECT synonym_name, table_owner, table_name
FROM all_synonyms
WHERE synonym_name = 'emp';

After executing this command, Oracle will return the synonym name, base table Information about schema and base table names.

Summary

Through the above introduction, we can understand how to create synonyms and how to query synonyms in Oracle. In practical applications, synonyms can help us simplify code, improve readability and maintainability. Appropriate use of synonyms is very helpful for database development and management.

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