使用coalesce函数只要超过一个expression，就会报错

使用coalesce函数只要超过一个expression，就会报错：
FAILED: ODPS-0130071:Semantic analysis exception - Expression not in GROUP BY key : line 8:9 ''$.table''

sql如下：
SELECT
md5(concat(aid,bid)) as id
,aid
, bid
, sum(amountdue) as amountdue
, coalesce(

sum(regexp_count(get_json_object(extended_x, '$.table.tableParties'), '{')),
decode(get_json_object(extended_x, '$.table'), NULL, 0, 1)

) as tableparty
, decode(sum(headcount),null,0,sum(headcount) ) as headcount
, 'a' as pt
FROM e_orders
where pt='20170425'
group by aid, bid