請教一下SQL

系SAS入邊見人用SQL, 但睇唔明, 請問有沒人知以下3句SQL 咩意思?


sum(  calculated x2 , calculated unhandle) as pend "pending",
==>SUM入邊calculated x2有咩特別意思? 

calculated x4  as Fail "Fil cases" ==>calculated x4 有咩特別意思

group by 1,2,3 / order by 1,2,3; ==>1,2,3又指咩?



======================================
proc sql;
create table A as
select

zone,
count(*) as total,
sum(j) as x1 "Passed",
sum(k) as x2 "Sent",
sum(l) as x3 "Confirmed",
,sum(m) as x4 "Not"
,sum(n) as x5 "Set"
,sum(o)as x6 "conditions"
sum(p) as x7 "Passed by",
count(case when q=0 then zone end) as unhandle "No",
1-((calculated  unhandle)/ calculated total) as cov,
sum(  calculated x2 , calculated unhandle) as pend "pending",
calculated x4  as Fail "Fail cases"

from B where zoneno="XXX"
group by 1,2,3
order by 1,2,3;
quit;