I know the one is a Dragon fruit cactus but I don't know the species. The second I'm not sure what it is! Thanks!!

The first one looks more like a Euphorbia to me.

None of this batch is Dragon fruit. The one you posted earlier may be.

Oh wow... the green house had the second labeled as a dragon fruit cactus

I'm assuming you're a student, and while I don't like to divert people from this site, this may help you with your studies of cactus
http://cactiguide.com/ You can't get it all from the easiest source.

1. Euphorbia
2. maybe

Dog-Tail Cactus (Deamia testudo)

We do have an epiphyllums and a cactus and succulents forums on here that you could peruse?

agree with #1. an Euphorbia, though I'm not sure of the sp, could be E horrida or hybrid. one clue (of some other) to easily distinguish Euphorbia from cacty is by removing one of those spine, or those tiny leaves, or by wound the stem just a litle, all euphorbia will bleed milky sap, while none of cactaceae will.
#2, Still possible for a dragon fruit I guess, is this grown from seeds?, I grow Selenicereus megalanthus and Hylocereus Sp from seeds, and at the young stage they could look like that. but if you grow from cuttings of mature plant it is different.

Yes I am a biology student! Especially obsessed with botany. Sorry to always bombard the site with questions, I'm just so curious and am constantly obtaining new plants (: The potential dragon fruit was grown from seed they told me! So I do know that!

Always appreciative of the help, I've learned so much from you all!

@baja_costero ... wow that does look VERY similar....

Dragon fruit (Hylocereus) would be 3 sided. Your plant has 4 sided stems. S. testudo may have 3-8 ribs. An old name (synonym) for the plant is Selenicereus.

Baja_Costero said:1. Euphorbia
2. maybe

Dog-Tail Cactus (Deamia testudo)