Ecto.Query.union
You're seeing just the macro
union
, go back to Ecto.Query module for more information.
A union query expression.
Combines result sets of multiple queries. The select
of each query
must be exactly the same, with the same types in the same order.
Union expression returns only unique rows as if each query returned
distinct results. This may cause a performance penalty. If you need
to combine multiple result sets without removing duplicate rows
consider using union_all/2
.
Note that the operations order_by
, limit
and offset
of the
current query
apply to the result of the union.
Keywords example
supplier_query = from s in Supplier, select: s.city
from c in Customer, select: c.city, union: ^supplier_query
Expressions example
supplier_query = Supplier |> select([s], s.city)
Customer |> select([c], c.city) |> union(^supplier_query)