请解释以下查询的原因:
select in.status as "no_installments"
, count(in.id) as "installment"
FROM instalsched.instalment in
GROUP BY in.status;
返回
ORA-00936:缺少表达式 00936。00000 -“缺少表达式” *原因:
*操作:行错误:1 列:12