提交具有相同输入字段的表单（与上次相同）时，如何在数据库中增加值

Question

I want a value (not the the id value BTW) to increment when the user submits the same value in input field.

For example lets say the value is in "number" column in db table and each time a user submits the form with lets suppose "hello" in input field the integer value in "number" column increments by a specific value.

Answer 1

You have to use trigger functions for this task, because in table there possible only one autoincrement key

If you use postgres you can use

create or replace function increment_version() returns trigger as $$
declare 
    new_version integer;
begin
    select max(version) into new_version from YOU_TABLE_NAME where CONDITIONS_YOU_NEED;
    new.version = new_version + 1;
    return new;

create trigger increment_version after insert on YOUR_TABLE_NAME
for each row execute increment_version();

Also you can use rules to complete this task

create rule increment_version as on insert to YOUR_TABLE
do update YOUR_TABLE set version=versino+1 where id = new.id;

But note, that in case of error trigger will give you an exception, but rule - not

rules in pg https://www.postgresql.org/docs/8.2/static/rules-update.html triggers in pg https://www.postgresql.org/docs/9.6/static/plpgsql-trigger.html

If you use mysql you can also use triggers but the syntax is a bit different https://dev.mysql.com/doc/refman/5.5/en/trigger-syntax.html

create trigger version after insert on YOUR_TABLE for each row begin
begin
    select max(version) into new_version from YOU_TABLE_NAME where CONDITIONS_YOU_NEED; 
    set new.version = new_version;
end;

Answer 2

I found the code. This is in PHP 5.(something).
Here is the code:

if(isset($_POST["Form input"])) {

$input=$_POST["input"];
$ip = getenv("REMOTE_ADDR");
$date=date("d M Y -- H");
$qry_get="select * from `table` where col = '".$input."'";
$qry_get_run=mysql_query($qry_get);
if ($qry_get_run) {
  $ret=mysql_num_rows($qry_get_run);
  if ($ret==0) {


    $qry_ins="INSERT INTO `table` (`col 1`, `col 2`, `col 3`) VALUES ('val1', 'val2', 'val3')";
    $qry_ins_run=mysql_query($qry_ins);
    if ($qry_ins_run) {
      echo "success message";
    }else{
      echo mysql_error();
    }
  }else{
     while ($get=mysql_fetch_assoc($qry_get_run)) {
        $val2=$get['col 2'];
        $id=$get['id'];



        $up_val=$val2+3;


        $qry = "update table_name set `col 2`='".$up_val."' where id='".$id."' ";
        $qry_run=mysql_query($qry);

     }
   }
 }
}