Error when executing insertion query

Question

How to avoid duplicate data before inserting. I used the below code but I'm getting this error.

No column name was specified for column 1 of 'temp'.

No column name was specified for column 2 of 'temp'.

No column name was specified for column 3 of 'temp'.

No column name was specified for column 4 of 'temp'.

No column name was specified for column 5 of 'temp'.

No column name was specified for column 6 of 'temp'.

No column name was specified for column 8 of 'temp'.

No column name was specified for column 9 of 'temp'.

Invalid column name 'datelist'.

  using (SqlConnection con2 = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString))
        {
            var fromdate = DateTime.Parse(txtfromdate.Text);
            var todate = DateTime.Parse(txttodate.Text);
            var datedif1 = (todate - fromdate).Days;

            var sqlInsert = new SqlCommand("INSERT INTO datelist ([datedif],[batch],[daywk],[semester],[weekbatch],[subject],[facultyname],[facultyid],[WeekMonth])  SELECT * from (SELECT @datedif,@batch,@daywk,@semester,@weekbatch,@subject,@facultyname,@facultyid,@weekMonth) AS temp WHERE NOT EXISTS (SELECT datelist,batch from datelist where batch=@batch and datedif=@datedif)", con2);

            var sqlParamater = sqlInsert.Parameters.Add("@datedif", SqlDbType.Date);
            var sqlParameter1 = sqlInsert.Parameters.Add("@batch", SqlDbType.NVarChar);
            var sqlParameter2 = sqlInsert.Parameters.Add("@daywk", SqlDbType.NVarChar);
            var sqlParameter3 = sqlInsert.Parameters.Add("@semester", SqlDbType.NVarChar);
            var sqlParameter4 = sqlInsert.Parameters.Add("@weekbatch", SqlDbType.NVarChar);
            var sqlParameter5 = sqlInsert.Parameters.Add("@subject", SqlDbType.NVarChar);
            var sqlParameter6 = sqlInsert.Parameters.Add("@facultyname", SqlDbType.NVarChar);
            var sqlParameter7 = sqlInsert.Parameters.Add("@facultyid", SqlDbType.NVarChar);
            var sqlParameter8 = sqlInsert.Parameters.Add("@WeekMonth", SqlDbType.NVarChar);

            con2.Open();
           // try
            //{
                for (var i = 0; i <= datedif1; i++)
                {
                    var consecutiveDate = fromdate.AddDays(i);

                    sqlParamater.Value  = consecutiveDate;
                    sqlParameter1.Value = batch1;
                    sqlParameter2.Value = dayweek;
                    sqlParameter3.Value = semester;
                    sqlParameter4.Value = weekbatch;
                    sqlParameter5.Value = subject;
                    sqlParameter6.Value = faculty;
                    sqlParameter7.Value = facultyid;
                    sqlParameter8.Value = weekmonth;

                    int s = sqlInsert.ExecuteNonQuery();
                }

            }

Answer 1

I'll admit to not having tested this, but given the error message, the subquery:

SELECT 
    @datedif,
    @batch,
    -- and so on
    @weekMonth
) AS temp

needs to have column names defined, as the value comes from a variable.

That would be:

SELECT 
    @datedif as datedif,
    @batch as batch,
    -- and so on
    @weekMonth as weekMonth
) AS temp

Answer 2

The error you are getting says it all. it's because your inner select table temp needs to have all the column names defined. Also in your WHERE NOT EXISTS (SELECT datelist , you are using your table name datelist as a column name.

To fix your error write your sql like this.

INSERT INTO datelist ([datedif],[batch],[daywk],[semester],[weekbatch],[subject],[facultyname],[facultyid],[WeekMonth])  
SELECT * FROM 
(
    SELECT @datedif as datedif,@batch as batch,@daywk AS batch,@semester AS semester,@weekbatch AS weekbatch,@subject AS subject,@facultyname AS facultyname,@facultyid AS facultyid,@weekMonth AS weekMonth 
) AS temp 
 WHERE NOT EXISTS (SELECT * from datelist where batch=@batch and datedif=@datedif);

You can alternately write your query in IF NOT EXISTS(SELECT){Insert} format like below. If you need to catch when a record already exists in database, you can add an ELSE with RAISERROR / THROW

IF NOT EXISTS(SELECT * from datelist where batch=@batch and datedif=@datedif )
BEGIN
    INSERT INTO datelist ([datedif],[batch],[daywk],[semester],[weekbatch],[subject],[facultyname],[facultyid],[WeekMonth])
    VALUES (@datedif,@batch,@daywk,@semester,@weekbatch,@subject,@facultyname,@facultyid,@weekMonth)
END
ELSE 
BEGIN
     RAISERROR('Record already exists in the table',16,1);
END