Do this instead
select ID,FULLADDRESS,CUSTOMERADDR1,CUSTOMERADDR2,LANDMARK,CITY,STATE, PINCODE from customerloandata
with (nolock) where CITY =''or STATE ='' or PINCODE = '' and isnull(addrverify,'NO') = 'NO'
If addrverify is a varchar, you cannot replace a null value with a number. Stick with the same datatype.