Those are different in Pronunciation and Feeling... If you can say Mandarin,and you can go everywhere in chia...

The difference between Mandarin and Shanghaiese is that: one can be understood by all chinese one can be only understood by the people in shanghai.

don't need to learn shanghaiese, mandarin is useful enough

Mandarin is a language which every Chinese can understand. In China everyone should study it. But shanghaiese is a local language, if you can understand Mandarin,you just can understand a little Shanghaiese if they speak slowly.

Mandarin is ubiquity language in china,Shanghaiese is a kind of local language in shanghai.