There is NO default "sort" order. Rows in a relational table are not sorted.
The only (really: the only) way to get a specific order is to use an ORDER BY
Whatever order you see when running a SELECT
without ORDER BY
is pure coincident and can change with the next execution.
The order can change because of various reasons:
- other sessions are running the same statement
- the table was updated
- the execution plan changes
- ...
Here is a little SQLFiddle that shows you how the "order" can change: http://sqlfiddle.com/#!4/19d14/2
Note that the initial "order" is not even the same as the insertion order!