burning question.

this question has been burning in my mind since I realized I cant play a full song but the parts I know show in my playing (in style not the actual riff, lick, etc). do you think its really important to your playing to entire songs or do you think just learning the parts you really like is sufficient? I would really like to know your opinions.

entire song all the way,aside from learning some licks,you will learn chords,progressions,construccion and structure.

I don't think you need to be able to play every song all the way through. I learn the parts of songs I really like. Also, I learned the whole first side of 2112.

It's not required of you(nothing in music is) but it certainly helps you learn a style much easier. For example: When I learned Master of Puppets by Metallica, I couldn't even come close to down picking any of it. It was simply too fast and way too taxing at the time.
After 6 months of practice I can down pick quite well and I have seen improvements across the board in my playing. Playing multiple songs all the way through is good if you are trying to immerse yourself into the style and genre, but at some point you need to have a select few that you can play all the way through(preferable that they are your favorite songs to play), and keep working on them. Always perfecting the spots that give you trouble, working on technique, etc.
Plus the feeling you will get from knowing you just jammed a song start to finish is great :)
Once you feel that you have basically mastered the song, find a new one to learn that's going to challenge you(learning the clean guitar parts on Fade to Black helped me to somewhat learn how to utilize hybrid picking).
Hope this helps dude.

thanks every one. Do you think learning songs all the way through may helped right songs? I think their could be a connection because I cant write full songs ether, just parts.

songs are just made up of parts dude. just take some of the progressions you have and start trying to fit them together.

Depends what song, but usually Alex is perfectly right on this. If it's like, a Ramones song or something that's just the same the whole way through I wouldn't bother memorizing it though. Just take as much knowledge as you can from everything dude, it'll help in the long run. And don't look at it as a chore either, that's a huge setback most of the time.

case- are you upstroke dominate?