不可以使用case when 的列名進行group by，如：

select count(1)/7 as "平均違法數量",
to_char(wfsj, 'yyyy-MM-dd' ) as time,
case
when (to_char(wfsj, 'hh24')) between 00 and 04 then
'00-04時'
when (to_char(wfsj, 'hh24')) between 04 and 08 then
'04-08時'
when (to_char(wfsj, 'hh24')) between 08 and 12 then
'08-12時'
when (to_char(wfsj, 'hh24')) between 12 and 16 then
'12-16時'
when (to_char(wfsj, 'hh24')) between 16 and 20 then
'16-20時'
when (to_char(wfsj, 'hh24')) between 20 and 24 then
'20-24時'
end as "違法時間"
from
vio_violation
where wfsj >= trunc(sysdate - 7)
group by "違法時間"；

正確sql：

select count(1)/7 as "平均違法數量",
to_char(wfsj, 'yyyy-MM-dd' ) as time,
case
when (to_char(wfsj, 'hh24')) between 00 and 04 then
'00-04時'
when (to_char(wfsj, 'hh24')) between 04 and 08 then
'04-08時'
when (to_char(wfsj, 'hh24')) between 08 and 12 then
'08-12時'
when (to_char(wfsj, 'hh24')) between 12 and 16 then
'12-16時'
when (to_char(wfsj, 'hh24')) between 16 and 20 then
'16-20時'
when (to_char(wfsj, 'hh24')) between 20 and 24 then
'20-24時'
end as "違法時間"
from
vio_violation
where wfsj >= trunc(sysdate - 7)
group by wfsj；

轉載于:https://www.cnblogs.com/ww5566/p/11124851.html

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