Order all entries by the following rule

Order by ascending deadline date basically, but rows that have null
deadline time are last.

Ex.

before:
2013-09-30 ?
2013-11-12 12:00
2013-09-30 00:30

after:
2013-09-30 00:30
2013-09-30 ?
2013-11-12 12:00
Order entries of searching result by the following rule

Order by ascending deadline date basically, but rows that have null
deadline time are last.

Ex.

before:
2013-09-30 ?
2013-11-12 12:00
2013-09-30 00:30

after:
2013-09-30 00:30
2013-09-30 ?
2013-11-12 12:00