How to insert the next highest number into the database

Question

I have a piece of mysqli code which I written where it will insert values into the database:

$insertsql = \"
INSERT INTO Teacher
    (TeacherId, TeacherForename,         


        

Answer 1

Change TeacherId from a varchar to an int. The create table will look a bit like this:

CREATE TABLE Teacher (
   TeacherId int unsigned not null auto_increment primary key

The auto_increment will start from 1 and automatically increase by 1 on each insert.

If you must prepend the T, you can always do it with CONCAT or in the php code.

Answer 2

Well you can try this:

First get the total number of rows in the table and increment it by 1 and put that into your new id For example:

$selectUsers = mysql_query ("SELECT * FROM `Teacher`") or die(mysql_error());
$num_rows = mysql_num_rows($selectUsers);

$next_id = $num_rows+1;

$new_id = 'T'.$next_id ;

and after insert it into the table:

...

Answer 3

You could do something like this. It is an auto incrementing primary key column with a formatted column. I have not had a chance to test this.

CREATE TABLE Teacher (
  TeacherId mediumint UNSIGNED AUTO_INCREMENT PRIMARY_KEY,
  TeacherIdF varchar(6) AS 'T_' + CONVERT(varchar, TeacherId),
  ...
  CONSTRAINT Teacher_UKey01 UNIQUE (TeacherIdF)
)

If the constraint does not work, you can create a trigger that will update the column after a row is inserted.

CREATE TABLE Teacher (
  TeacherId mediumint UNSIGNED AUTO_INCREMENT PRIMARY_KEY,
  TeacherIdF varchar(6) NULL
  ...
)

CREATE TRIGGER FormattedTeacherId
AFTER insert ON Teacher
BEGIN
UPDATE Teacher SET TeacherIdF = CONCAT('T', TeacherId)
END

I have not tested this code.