SQL Function in Oracle

TOP

SQL Server:

SELECT TOP 10 product, descr, email
FROM products

ORACLE:

SELECT product, descr, email
FROM products
WHERE ROWNUM < = 10

MySQL:

SELECT product, descr, email
FROM products
LIMIT 10

Oracle Database and C# : SQL Function

Function for Query
ex : SELECT

        public DataSet ExecuteQuery(string sql)
        {
            DataSet dsResult = new DataSet();

            try
            {
                OracleDataAdapter daAdapter = new OracleDataAdapter(sql, conn);
                daAdapter.Fill(dsResult);
            }
            catch (OracleException oex)
            {
                if (oex.Number == 2292)
                    MessageBox.Show("crash from a data from other table");
                else
                    MessageBox.Show(oex.Message);

                CloseConnection();
                OpenConnection();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);

                CloseConnection();
                OpenConnection();
            }

            return dsResult;
        }

Function for DML
ex : UPDATE, DELETE

        public int ExecuteSQL(string sql)
        {
            int isAffectedRows = 0;

            try
            {
                OracleTransaction oTransaction = conn.BeginTransaction();
                OracleCommand oCmd = conn.CreateCommand();
                oCmd.CommandText = sql;
                isAffectedRows = oCmd.ExecuteNonQuery();
                oTransaction.Commit();
            }
            catch (OracleException oex)
            {
                if (oex.Number == 2292)
                {
                    MessageBox.Show("crash from a data from other table");
                }
                else
                {
                    MessageBox.Show(oex.Message);
                }

                CloseConnection();
                OpenConnection();

                return 0;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);

                CloseConnection();
                OpenConnection();

                return 0;
            }

            return isAffectedRows;  // if success return value not 0
        }

Oracle Database Connection using C#

what we must do first :

private OracleConnection conn;
private string connString = "Data Source=(DESCRIPTION="
             + "(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=10.126.11.15)(PORT=1521)))"
             + "(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=ORAPBD9)));"
             + "User Id=joe;Password=joe;";

for opening connection :

public bool OpenConnection()
{
            bool success = true;

            try
            {
                conn = new OracleConnection(connString);
                conn.Open();
            }
            catch (Exception ex)
            {
                success = false;
            }

            return success;
}

closing….

public void CloseConnection()
{
        conn.Close();
        conn.Dispose();
}