我努力让这与Postgres的和外生的工作。下面的查询工作正常无GROUP_BY,但我需要组片段场,这似乎也无法看到。任何想法有什么错呢?
def query_clicks do
from(Click)
|> select(
[c],
[
fragment("date_trunc('hour',?) as hour", c.inserted_at), c.link_id]
)
|> group_by([c], c.hour)
|> Repo.all
end
结果:
iex(1)> recompile; Shortr.LinkContext.query_clicks
[debug] QUERY ERROR source="clicks" db=1.2ms queue=4.9ms
SELECT date_trunc('hour',c0."inserted_at") as hour, c0."link_id" FROM "clicks" AS c0 GROUP BY c0."hour" []
** (Postgrex.Error) ERROR 42703 (undefined_column) column c0.hour does not exist
query: SELECT date_trunc('hour',c0."inserted_at") as hour, c0."link_id" FROM "clicks" AS c0 GROUP BY c0."hour"
(ecto_sql) lib/ecto/adapters/sql.ex:604: Ecto.Adapters.SQL.raise_sql_call_error/1
(ecto_sql) lib/ecto/adapters/sql.ex:537: Ecto.Adapters.SQL.execute/5
(ecto) lib/ecto/repo/queryable.ex:147: Ecto.Repo.Queryable.execute/4
(ecto) lib/ecto/repo/queryable.ex:18: Ecto.Repo.Queryable.all/3
iex(1)>
在生成的SQL调用c0.hour
而你别名列hour
。它应该是
SELECT date_trunc('hour',c0."inserted_at") as hour, c0."link_id" FROM "clicks" AS c0 GROUP BY hour
在这种外生将成为
def query_clicks do
from(Click)
|> select(
[c],
[
fragment("date_trunc('hour',?) as hour", c.inserted_at), c.link_id
]
)
|> group_by([c], fragment("hour"))
|> Repo.all
end
另一个问题是link_id
,SELECT子句中的任何字段必须出现在GROUP BY子句或者是一个汇集起来。您例如,还通过集团可能link_id
。