PHP表单中的数据被多次插入到mysql数据库中

Question

I'm pretty new in PHP and MYSQL. I've got this form that I use to enter data into a database I created. I add up values from two fields in separate columns and insert the value into a third column (TOTAL_IN). Then I subtract another value (VALUE3) that's in another field from the value in a field in the third column (TOTAL_IN) and put that value in a different column. All these are in the same table. It works just fine, but the problem is that when I open up my database I see that the data has been inserted 20 or 100 times! How can I stop the data from being inserted so many times?

Please note that the submit button was clicked only once.

Here is what I use:

$sql="INSERT INTO $tbl_name (id, date, value1, value2, total_in, value3, value4)
      SELECT '','$date','$value1','$value2',('$value1'+'$value2') AS SUM,
              '$value3',(('$value1'+'$value2')-$value3) AS SUM
      FROM $tbl_name";
$result=mysql_query($sql);

any help?

Thanks in advance!

EDIT::: Here is what my code looks like now after your suggestions:

//From Ruddy's post
$total_in=$value1+$value2;
$value4=($value1+$value2)-$value3;

//From Amit's post
$sql="INSERT INTO $tbl_name(id, date, value1, value2, total_in, value3, value4) VALUES ('', '.$date.', '.$value1.', '.$value2.', '.$total_in.', '.$value3.', '.$value4.')";
$result=mysqli_query($sql);

it works but it still enters the data many times.

Answer 1

$sql="INSERT INTO $tbl_name (id, date, value1, value2, total_in, value3, value4)
 VALUES( '', '".$date."', ".$value1.", ".$value2.", ".$value1+$value2.", 
".$value3.",".$value1+$value2-$value4.")";
$result=mysql_query($sql);

You need to concatenate the variables in php while writing in the query please see the syntax.

see here

What you were doing was select all the rows of the table and inserting into all.