markdown Oracle Drop If Exists.md

Posted 2021-05-06

From [Oracle: If Table Exists](https://stackoverflow.com/questions/1799128/oracle-if-table-exists):

The best and most efficient way is to catch the "table not found" exception: this avoids the overhead of checking if the table exists twice; and doesn't suffer from the problem that if the DROP fails for some other reason (that might be important) the exception is still raised to the caller:

    BEGIN
       EXECUTE IMMEDIATE 'DROP TABLE mytable';
    EXCEPTION
       WHEN OTHERS THEN
          IF SQLCODE != -942 THEN
             RAISE;
          END IF;
    END;

**ADDENDUM**
For reference, here are the equivalent blocks for other object types:

Sequence

    BEGIN
      EXECUTE IMMEDIATE 'DROP SEQUENCE ' || sequence_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -2289 THEN
          RAISE;
        END IF;
    END;

View

    BEGIN
      EXECUTE IMMEDIATE 'DROP VIEW ' || view_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -942 THEN
          RAISE;
        END IF;
    END;

Trigger

    BEGIN
      EXECUTE IMMEDIATE 'DROP TRIGGER ' || trigger_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -4080 THEN
          RAISE;
        END IF;
    END;

Index

    BEGIN
      EXECUTE IMMEDIATE 'DROP INDEX ' || index_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -1418 THEN
          RAISE;
        END IF;
    END;

Column

    BEGIN
      EXECUTE IMMEDIATE 'ALTER TABLE ' || table_name
                    || ' DROP COLUMN ' || column_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -904 THEN
          RAISE;
        END IF;
    END;

Database Link

    BEGIN
      EXECUTE IMMEDIATE 'DROP DATABASE LINK ' || dblink_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -2024 THEN
          RAISE;
        END IF;
    END;

Materialized View

    BEGIN
      EXECUTE IMMEDIATE 'DROP MATERIALIZED VIEW ' || mview_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -12003 THEN
          RAISE;
        END IF;
    END;

Type

    BEGIN
      EXECUTE IMMEDIATE 'DROP TYPE ' || type_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -4043 THEN
          RAISE;
        END IF;
    END;

Constraint

    BEGIN
      EXECUTE IMMEDIATE 'ALTER TABLE ' || table_name
                || ' DROP CONSTRAINT ' || constraint_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -2443 THEN
          RAISE;
        END IF;
    END;

Scheduler Job

    BEGIN
      DBMS_SCHEDULER.drop_job(job_name);
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -27475 THEN
          RAISE;
        END IF;
    END;

User / Schema

    BEGIN
      EXECUTE IMMEDIATE 'DROP USER ' || user_name;
      /* you may or may not want to add CASCADE */
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -1918 THEN
          RAISE;
        END IF;
    END;

Package

    BEGIN
      EXECUTE IMMEDIATE 'DROP PACKAGE ' || package_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -4043 THEN
          RAISE;
        END IF;
    END;

Procedure

    BEGIN
      EXECUTE IMMEDIATE 'DROP PROCEDURE ' || procedure_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -4043 THEN
          RAISE;
        END IF;
    END;

Function

    BEGIN
      EXECUTE IMMEDIATE 'DROP FUNCTION ' || function_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -4043 THEN
          RAISE;
        END IF;
    END;

Tablespace

    BEGIN
      EXECUTE IMMEDIATE 'DROP TABLESPACE' || tablespace_name;
    EXCEPTION
      WHEN OTHERS THEN
        IF SQLCODE != -959 THEN
          RAISE;
        END IF;
    END;