ORA-00909: Invalid Number of Arguments — Causes, Fixes, and Prevention

ORA-00909 is a parse-time error thrown by Oracle Database when a built-in or user-defined function is called with the wrong number of arguments. Because it occurs during the SQL parsing phase — before any data is actually accessed — the query fails immediately and no rows are returned. This error is common among developers who work across multiple database platforms or those who call PL/SQL functions whose signatures have changed.

Top 3 Causes

1. Wrong Argument Count for a Built-in Function

The most frequent cause is simply passing too few or too many arguments to Oracle built-in functions like NVL, SUBSTR, ROUND, or DECODE.

-- WRONG: NVL requires exactly 2 arguments
SELECT NVL(employee_name)
FROM employees;
-- ORA-00909: invalid number of arguments

-- WRONG: ROUND accepts only 1 or 2 arguments
SELECT ROUND(salary, 2, 'UP')
FROM employees;
-- ORA-00909: invalid number of arguments

-- CORRECT
SELECT NVL(employee_name, 'N/A') FROM employees;
SELECT ROUND(salary, 2)          FROM employees;
SELECT SUBSTR(last_name, 1, 5)   FROM employees;

2. Calling a User-Defined Function After a Signature Change

When a PL/SQL function or package procedure is modified — parameters added, removed, or reordered — any calling SQL or application code that isn't updated will trigger ORA-00909.

-- Check current parameter spec before calling
SELECT argument_name,
       position,
       data_type,
       in_out,
       defaulted
FROM   all_arguments
WHERE  object_name = 'GET_EMPLOYEE_INFO'  -- uppercase
AND    owner       = 'HR'
ORDER BY position;

-- WRONG: function now requires 2 params, but only 1 is passed
SELECT get_employee_info(101)
FROM dual;
-- ORA-00909: invalid number of arguments

-- CORRECT: pass all required arguments
SELECT get_employee_info(101, 'FULL')
FROM dual;

3. Dynamic SQL Building Incorrect Function Calls at Runtime

In dynamic SQL scenarios using EXECUTE IMMEDIATE or DBMS_SQL, argument values can be accidentally omitted during string concatenation, causing ORA-00909 only under specific runtime conditions.

DECLARE
    v_col    VARCHAR2(50)   := 'SALARY';
    v_defval VARCHAR2(50)   := '0';
    v_sql    VARCHAR2(1000);
    v_result NUMBER;
BEGIN
    -- WRONG: second argument for NVL is missing
    -- v_sql := 'SELECT NVL(' || v_col || ') FROM employees WHERE ROWNUM = 1';

    -- CORRECT: build the full, valid function call
    v_sql := 'SELECT NVL(' || v_col || ', ' || v_defval || ') '
          || 'FROM employees WHERE ROWNUM = 1';

    DBMS_OUTPUT.PUT_LINE('SQL: ' || v_sql);  -- log before execution
    EXECUTE IMMEDIATE v_sql INTO v_result;
    DBMS_OUTPUT.PUT_LINE('Result: ' || v_result);
EXCEPTION
    WHEN OTHERS THEN
        DBMS_OUTPUT.PUT_LINE('Failed SQL: ' || v_sql);
        DBMS_OUTPUT.PUT_LINE('Error: ' || SQLERRM);
        RAISE;
END;
/

Quick Fix Checklist

1. Identify the offending function — read the full error stack; Oracle usually points to the line number.
2. Check the correct signature — use ALL_ARGUMENTS or consult the Oracle SQL Language Reference.
3. Count your arguments — compare what you passed against what the function expects.
4. For dynamic SQL — always DBMS_OUTPUT.PUT_LINE the assembled string before executing it.

Prevention Tips

• Use an IDE with live syntax validation — tools like SQL Developer, Toad, or DBeaver highlight argument mismatches before you run the query.
• Version-control function signatures — whenever a PL/SQL function's parameter list changes, run an impact analysis against ALL_ARGUMENTS and update all callers as part of the same release.

-- Find all objects that call a specific function (quick impact check)
SELECT name, type, line, text
FROM   all_source
WHERE  UPPER(text) LIKE '%GET_EMPLOYEE_INFO%'
AND    owner = 'HR'
ORDER BY name, line;

Related Errors

📖 Want a more detailed guide?
Check out the full in-depth version (Korean) on oraerror.com — includes detailed analysis, additional SQL examples, and prevention tips.