What are the differences between survey & questionnaire?

Questionaire is a kind of tool to be used to do the survey.

survey 係「調查」，分好多種，例如 1 to 1 interview、focus group、online questionaire、observation、觀察等等~~

questionnaire 係「問卷」，係調查的一種。

Survey: an activity
Questionnaire: one of the tools for the survey activity