Why should you care?

Batch jobs in telecom billing must log bad rows and continue — not stop the whole night run.

See it live — copy this example

Run these statements in SQL Developer or SQL*Plus against your lab PDB. Prefer a practice user — not SYS — for application SQL.

DECLARE
  v_bal NUMBER;
  v_id  NUMBER := 999;
BEGIN
  SELECT balance INTO v_bal FROM customers WHERE customer_id = v_id;
  DBMS_OUTPUT.PUT_LINE('Balance=' || v_bal);
EXCEPTION
  WHEN NO_DATA_FOUND THEN
    DBMS_OUTPUT.PUT_LINE('Customer ' || v_id || ' not found');
  WHEN OTHERS THEN
    DBMS_OUTPUT.PUT_LINE('Error: ' || SQLERRM);
    RAISE;
END;
/

What happened?

• SELECT INTO expects exactly one row.
• NO_DATA_FOUND runs if zero rows.
• WHEN OTHERS is a safety net; RAISE re-throws after logging.

Practice next

1. SET SERVEROUTPUT ON in SQL*Plus/SQL Developer.
2. Run the block with a missing id.
3. Change v_id to an existing customer.
4. Raise a custom error with RAISE_APPLICATION_ERROR.
5. Write the error into an error_log table.

Remember

Catch expected errors explicitly. Log SQLERRM for support. Do not hide failures in empty handlers.

Nightly billing batch

One bad account must not stop 2 million invoice rows.

Outcome: Handler logs the bad id and continues.