Because OTHERS handles all exceptions, you must list it after any specific exceptions in your EXCEPTION block. : Exception « PL SQL Programming « Oracle PL/SQL Tutorial

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SQL>
SQL> BEGIN
  2     DBMS_OUTPUT.PUT_LINE(1 / 0);
  3  EXCEPTION
  4     WHEN OTHERS THEN
  5        DBMS_OUTPUT.PUT_LINE('An exception occurred');
  6     WHEN ZERO_DIVIDE THEN
  7        DBMS_OUTPUT.PUT_LINE('Division by zero');
  8  END;
  9  /
   WHEN OTHERS THEN
   *
ERROR at line 4:
ORA-06550: line 4, column 4:
PLS-00370: OTHERS handler must be last among the exception handlers of a block
ORA-06550: line 0, column 0:
PL/SQL: Compilation unit analysis terminated


SQL>