Cardinality to be none

Databases
1 
ALTER TABLE  `myTable` ADD INDEX (  `id`)

When I run the code above through phpMyAdin, it shows cardinality is “1467”.

Why does it become “1467”?
How can I make cardinality be “none” instead of “1467”?

(The number of records in myTable is 1467 at the moment.
I can’t add a new record to the table because, I guess, it is limited to 1467.)

2

run this query –

TRUNCATE TABLE `mytable`
3

The query, I think, will delete all records in myTable.
Can I ADD INDEX (‘id’) with cardinality be “none” without deleting any of records in myTable?

4

I made it myself with the procedure in the below.

(1) I copy myTable with a name of myTable2.
(2) TRUNCATE TABLE mytable
(3) ALTER TABLE myTable ADD INDEX ( id)
(4) copy all records in myTable2 into myTable while myTable2 is looping with SELECT * FROM myTable order by id

Thank you.
(Is there any easier way?)

5

will change the cardinality back to 1467 (if that is the number of records in the table).

To quote from the mySQL manual regarding what cardinality is:

Cardinality

An estimate of the number of unique values in the index. This is updated by running ANALYZE TABLE or myisamchk -a. Cardinality is counted based on statistics stored as integers, so the value is not necessarily exact even for small tables. The higher the cardinality, the greater the chance that MySQL uses the index when doing joins.