Hi Zongjie,
you can find some information about the creation of calculated columns in the HANA Modeling Guide (http://help.sap.com/hana/SAP_HANA_Modeling_Guide_for_SAP_HANA_Studio_en.pdf).
Within chapter 6.2.1 (Create Analytic Views) you can see under point 7 some basics and also a simple example. The same is also valid for Calculation Views.
Chapter 8.9 (Using Functions in Expressions) describes the different available functions.
You also can use the integrated search in the HANA Studio by clicking the "?" button in the button left corner. Then you get some links in the side panel with related information.
In general you can write your expression manually or you can just drag and drop the functions, elements, operators into the editor window. For example if you drag and drop the "if" function into the editor window you get "if(intarg,arg2,arg3)" inserted. The arguments can be replaced manually or also by drag and drop.
It is also worse to use the "Validate Syntax" button on top of the editor window. It gives you directly a feedback if your expression syntax is correct. If not you get some helpful information about the problem (ok, sometimes it is a little bit confusing because of the cryptic error message format 
).
Best Regards,
Florian