使用PHP和MySQL查询表中的重复值

Question

I need some help regarding MySQL query for checking duplicate value from table using MySQL and PHP. Let me to explain my table structure and conditions

db_product_info

pro_id     product_name      product_code      status

The above are my columns in db_product_info table.

conditions:

1-> When table has no value the data should entry in table.

2-> In same product name only same product code will be inserted for once/multiple time in table.If input will different code for same product name (for more than one enrty) it should be checked and return the validation message.

3- Duplicate of product_code will be checked according to the product_name as explained above.means for same product_name only same product_code should entry multiple time but this product_code should not used for any other product_name .

Let me to explain my code below.

 require_once("../include/dbconfig.php");
    $result=array();
    $fields=array("Product_name","status","product_code");
    $tablename=PREFIX."product_info";
$values=array($_POST['product_name'],$_POST['status'],$_POST['product_code']);
    $id=db_insert($tablename,$values,$fields);
                   if($id){
                $result[0]["msg"]="Added successfully";
                $result[0]['id']=$id;
                echo json_encode($result);
            }else{
                header("HTTP/1.0 401 Unauthorized");
                $result[0]["msg"]="Unable to add try again";
                $result[0]["data"]=$values;
                echo json_encode($result);
            }

Please help me to resolve this problem.