I am getting Invalid column error on acctkey column. Can you please tell me what am I doing wrong?
select COUNT(acctkey) as Num, case
when source_sys_cd in ('TRS','CLS') then source_sys_cd + '|'+[acct_num]
when source_sys_cd = 'Hogan CIS' and [acct_type_cd] = 'DDA' then 'DDA' + '|'+ [acct_id]
when source_sys_cd = 'Hogan CIS' and [acct_type_cd] != 'DDA' then 'TDA' +'|'+ [acct_id]
when source_sys_cd = 'CLN' then source_sys_cd + '|'+ [acct_num]+ [acct_id]
when source_sys_cd = 'RCC' then source_sys_cd + '|'+ [acct_id]
when source_sys_cd = 'ITF' then source_sys_cd + '|'+ [acct_id]+ [acct_num]
when source_sys_cd = 'SEC' then source_sys_cd + '|'+ [acct_id]
else source_sys_cd + '|'+ [acct_num]
end as acctkey
from mtb..STAGING_CUST_ACCT
group by source_sys_cd
,acct_id
,acct_num
,acctkey
,acct_type_cd