Ecto.Query.except

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except(query, other_query)

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An except (set difference) query expression.

Takes the difference of the result sets of multiple queries. The select of each query must be exactly the same, with the same types in the same order.

Except expression returns only unique rows as if each query returned distinct results. This may cause a performance penalty. If you need to take the difference of multiple result sets without removing duplicate rows consider using except_all/2.

Note that the operations order_by, limit and offset of the current query apply to the result of the set difference.

Keywords example

supplier_query = from s in Supplier, select: s.city
from c in Customer, select: c.city, except: ^supplier_query

Expressions example

supplier_query = Supplier |> select([s], s.city)
Customer |> select([c], c.city) |> except(^supplier_query)