How to Simulate MySQL's 'IF EXISTS' Functionality in Oracle?

Simulate MySQL’s IF EXISTS: Oracle database object processing method

In the process of migrating a database from MySQL to Oracle, you may wonder if there is a structure similar to "IF EXISTS" in order to handle objects that may not exist.

Equivalent method of IF EXISTS in Oracle

Although Oracle does not have an explicit "IF EXISTS" structure, there are some techniques to achieve similar functionality:

Catch "Object not found" exception

Delete table:

<code class="language-sql">BEGIN
   EXECUTE IMMEDIATE 'DROP TABLE ' || table_name;
EXCEPTION
   WHEN OTHERS THEN
      IF SQLCODE != -942 THEN
         RAISE;
      END IF;
END;</code>

23c version alternative syntax:

<code class="language-sql">BEGIN
   EXECUTE IMMEDIATE 'DROP TABLE IF EXISTS ' || table_name;
END;</code>

Equivalent code blocks for other object types

Oracle provides a similar exception handling code block for deleting other database objects:

Sequence:

<code class="language-sql">BEGIN
  EXECUTE IMMEDIATE 'DROP SEQUENCE ' || sequence_name;
EXCEPTION
  WHEN OTHERS THEN
    IF SQLCODE != -2289 THEN
      RAISE;
    END IF;
END;</code>

View:

<code class="language-sql">BEGIN
  EXECUTE IMMEDIATE 'DROP VIEW ' || view_name;
EXCEPTION
  WHEN OTHERS THEN
    IF SQLCODE != -942 THEN
      RAISE;
    END IF;
END;</code>

Summary

Although Oracle does not have a direct "IF EXISTS" syntax, the above exception handling techniques provide an efficient and reliable way to handle database objects that may not exist.

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