can we create number of fields at a time with same data type in mysql?
You can add several columns at once but you need to declare the types per column:

alter table t add column (s5 int, s6 int);


You can also use:

alter table t add (s5 int, s6 int);


but I prefer the first one. Note that the parentheses are mandantory.

You don't mention your version, but the syntax have been valid since at least 5.1:

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