Cambell,  Actually the user is default user in phpmyadmin.

the query is not working with the TR_PREF and $Cust_id. while using the above code.  And my query failed to work.

And i tried to show the sql queries by enabling the option on config.php.  but it showed " ROLLBACK"

What is the issue in it.

Is the table name really hard coded to be TB_PREFtable_name?  Or is table_name a variable in which case it should be $table_name.  It would make more sense to me for the column name you are adding to be a constant e.g. 'some_column' rather than a variable.

Does the database user have permission to alter table structure?  Most likely does worth checking though.

Check the syntax against this:

http://dev.mysql.com/doc/refman/5.1/en/alter-table.html
http://dev.mysql.com/doc/refman/5.1/en/create-table.html

You can also get good help on sql here:

http://stackoverflow.com/

ALTER TABLE  `0_users` ADD  `test` INT( 10 ) NOT NULL ;

I need to add a column using alter table query. here is the query string i used. but it dooesnot work for me.

$kv_sql = "ALTER TABLE ".TB_PREF."table_name ADD ".db_escape($cust_id)." INT(10) NOT NULL" ; 

    db_query($kv_sql, "The employee attendance could not be added");

But t doesnot work in it. 
i dont know the bug.