I just found out this usefu function in MSSQL when I try to Google for the solution to replace the null value with something else. So that I no need to do the checking again in my application. The function is call
NULLIF and ISNULL
This 2 functions are actually work opposite with each other.
NULLIF(ColumnName, ValueToCompare) accept 2 parameters, and will return the NULL value if both the expression match.
IFNULL(ColumnName, NewValue) accept 2 parameters, the first parameters is the string that you wish you check with, and the 2nd parameter that you wish to replace with.