In MATLAB, ... is used to continue a line to the next line. But if I want to continue a long string within quotation, what can I do? ... will be treated as a part of the string itself. Using [] is not a perfect solution since in most cases I use sprintf/fprintf to parse a long string like sql query. Using [] would be cumbersome. thanks. 

Note - this is related to character arrays, not strings, per se, which is a separate type in newer versions of Matlab a = 'a character array', b = "a string"  

Answers:

If you put the string in brackets, you can build it in several pieces: 

s = ['abc' 'def' ... 
     'ghi'];

You can then split that statement into several lines between the strings.