sql server - join table and where column similar to other column, while changing column value SQL -

i have issue code. sql issue.

i need combine 2 tables. @ present have code:

select calldate,clid, '44'+dst      [numberdialed],dstchannel,billsec,disposition,accountcode,uniqueid,cnam, callrateimport.description, callrateimport.code, callrateimport.day calllogimport left join callrateimport on calllogimport.dst callrateimport.code + '%' callrateimport.code(select code callrateimport calllogimport.dst code + '%' , len(code) = (select max(len(code)) callrateimport calllogimport.dst callrateimport.code + '%') ) 

this combining fine. need match altered result depending on original result is.

i have code:

if substring (dst,1,2)=00  begin  end 

wrapping current code. sql throwing errors - incorrect syntax. have else if block of 3 components.

to modify values based on current value, should @ case statements.

for example:

use adventureworks2012; go select   productnumber, category =     case productline        when 'r' 'road'        when 'm' 'mountain'        when 't' 'touring'        when 's' 'other sale items'        else 'not sale'     end,  name production.product order productnumber; go 

or searched case expressions:

use adventureworks2012; go select   productnumber, name, "price range" =       case          when listprice =  0 'mfg item - not resale'         when listprice < 50 'under $50'         when listprice >= 50 , listprice < 250 'under $250'         when listprice >= 250 , listprice < 1000 'under $1000'         else 'over $1000'      end production.product order productnumber ; go