check mysql_query result true or false

[lhbdan]

I have been trying to write code that deletes a book from a database if the user provides a BookName, and the corresponding DeletionCode. I then want to provide the user with feedback, telling the user whether they have deleted a book, that is they have provided a deletion code and a book name, or whether they have not deleted a book, because they have entered the wrong bookname or book ID. I thought this code would work, but it seems that the $result variable is always set as TRUE, no matter whether the code has deleted a row or not. What have i done wrong?

 

$result = mysql_query("DELETE FROM books WHERE BookName = '$_POST[bookName]' && DeletionCode = '$_POST[Deletioncode]'");

 

 

if(!$result){

die('Invalid query: ' . mysql_error());

}

else

echo "delete book";

 

[lhbdan]

sorry the last echo should say "deleted book"; not "delete book";

[DavidAM]

mysql_query() will only return false if the query fails - i.e. if it is invalid. A DELETE (or UPDATE) statement that does not affect any rows, is valid. Use mysql_affected_rows() to see how many rows were deleted.

[lhbdan]

thanks, so how will that fit into my code?

[DavidAM]

Something like this

 

if (! $result) {
  // Query Failed
} elseif (mysql_affected_rows() == 0) {
  // No such book
} else {
  // Book Deleted
}

[lhbdan]

thankyou!!!