How to Check for Table Existence and Perform Conditional DDL Operations in Oracle?

Conditional DDL operations in Oracle database: gracefully handle whether a table exists

Unlike MySQL, Oracle database has no direct IF EXISTS syntax for table operations. However, we can achieve similar functionality through the following methods.

Exception handling methods

The most efficient way is to catch the "table does not exist" exception:

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

This method avoids the need to check whether the table exists twice like other methods.

IF EXISTSSyntax (Oracle 23c and above)

Starting with Oracle version 23c, all DROP DDL operations support the simpler IF EXISTS syntax:

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

Alternatives for other object types

Similar exception handling blocks can be used for other Oracle object types:

• 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>

• Trigger:

<code class="language-sql">BEGIN
  EXECUTE IMMEDIATE 'DROP TRIGGER ' || trigger_name;
EXCEPTION
  WHEN OTHERS THEN
    IF SQLCODE != -4080 THEN
      RAISE;
    END IF;
END;</code>

• Index:

<code class="language-sql">BEGIN
  EXECUTE IMMEDIATE 'DROP INDEX ' || index_name;
EXCEPTION
  WHEN OTHERS THEN
    IF SQLCODE != -1418 THEN
      RAISE;
    END IF;
END;</code>

• Column:

<code class="language-sql">BEGIN
  EXECUTE IMMEDIATE 'ALTER TABLE ' || table_name
                || ' DROP COLUMN ' || column_name;
EXCEPTION
  WHEN OTHERS THEN
    IF SQLCODE != -904 AND SQLCODE != -942 THEN
      RAISE;
    END IF;
END;</code>

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