How can I? such as "select max(peak_kw) peak,month from sola_daylies group by month;"

Rails
#1

When I tried on mysql
select max(peak_kw) peak,month from sola_daylies group by month;
It returns as I expected
±-------±-----------+
| peak | month |
±-------±-----------+
| 0.2126 | 2014-12-01 |
| 1.6156 | 2015-01-01 |
±-------±-----------+

on rails console,
Sola::Dayly.find_by_sql(“select max(peak_kw) peak,month from
sola_daylies
group by month”)
log says, it makes sql command
select max(peak_kw) peak,month from sola_daylies group by month
It returns without column “peak”
[#<Sola::Dayly id: nil, month: “2014-12-01”>, #<Sola::Dayly id: nil,
month:
“2015-01-01”>]

Sola::Dayly.select(“max(peak_kw) peak”,:month).group(:month)
returns same.

#2

Try this:

Sola::Dayly.group(:month).maximum(:peak_kw)

Explanation:
“find_by_sql” is to be used to get real records, not database
calculations.
The “Group”, “Max” and other statements produce calculations, not real
records.

If you want to do a raw SQL, do with "
ActiveRecord::Base.connection.execute"

results = ActiveRecord::Base.connection.execute(“select max(peak_kw)
peak,month from sola_daylies group by month”)

pp results[0]

–
Daniel L.

#3

Thank you, I got it.

2015年1月20日火曜日 5時55分31秒 UTC+9 Daniel L.: