C# calling Oracle Function - Error: “Invalid operation on null data”

Question

I'm getting an error "Invalid operation on null data" when my C# code is calling Oracle Function. This happens only if no data is found. If data is found and function returns a value, then everything works ok. I'm a little confused, as - to my understanding at least - function should return 100 if no data found (see function exception).

Oracle Function:

create or replace FUNCTION F_SCO_DPD
(
    p_tip IN NUMBER,
    p_dav IN VARCHAR2
)
RETURN NUMBER 
IS
    sco NUMBER;
BEGIN
    SELECT max(score) keep(dense_rank first order by vrednost)
        INTO sco
        FROM sco_sif_score
        WHERE sif_kat = 11
        AND tip_pod = p_tip
        AND vrednost >= (SELECT a.dpd
                         FROM sco_dpd a                                      
                         WHERE a.par_davcna = p_dav);
    RETURN sco;
EXCEPTION
        WHEN NO_DATA_FOUND 
        THEN 
             RETURN 100;   
END F_SCO_DPD;

C# Code:

using (OracleCommand cmd = new OracleCommand())
{
    cmd.Connection = conn;
    cmd.CommandText = "F_SCO_DPD";
    cmd.CommandType = CommandType.StoredProcedure;
    cmd.Parameters.Add(new OracleParameter("p_tip", Podjetje.TipSub));
    cmd.Parameters.Add(new OracleParameter("p_dav", Podjetje.Davcna));
    cmd.Parameters.Add(new OracleParameter("sco", OracleDbType.Decimal, ParameterDirection.ReturnValue));
    cmd.BindByName = true;

    cmd.ExecuteScalar();

    Score.ScoDpd = (int)(OracleDecimal)cmd.Parameters["sco"].Value;                                    
}

Answer 1

You are running an aggregation function. max(score) keep (dense_rank first order by vrednost) is as much an aggregation function as max(score) .

That means that your query is an aggregation query with no GROUP BY . All such queries return exactly 1 row. If no rows match the WHERE clause, then the value is NULL .

So, the exception is never triggered. Instead, check if the returned value is NULL .

The resulting code is:

create or replace FUNCTION F_SCO_DPD
(
    p_tip IN NUMBER,
    p_dav IN VARCHAR2
)
RETURN NUMBER 
IS
    v_sco NUMBER;
BEGIN
    SELECT max(score) keep (dense_rank first order by vrednost)
    INTO v_sco
    FROM sco_sif_score
    WHERE sif_kat = 11 AND
          tip_pod = p_tip AND
          vrednost >= (SELECT a.dpd
                       FROM sco_dpd a                                      
                       WHERE a.par_davcna = p_dav
                      );

    RETURN COALESCE(v_sco, 100);
END F_SCO_DPD;