Sha256: 43614fc92d3096a2403addc9ec5d3e1e8f382e4bb836cefad08eadd971e12d37
Contents?: true
Size: 896 Bytes
Versions: 8
Compression:
Stored size: 896 Bytes
Contents
require 'alf'
module Database
include Alf::Viewpoint
def orders
Relation(
Tuple(oid: "O1", city: "London", amount: 100.00),
Tuple(oid: "O2", city: "Paris", amount: 100.00))
end
def discount_rules
Relation(
Tuple(city: "London", rule: ->{ amount * 0.20 }),
Tuple(city: "Paris", rule: ->{ amount * 0.15 }))
end
end
# Let open a connection on this database
db = Database.connect(Path.pwd)
# Compute the discount to apply according to the city
rel = db.query do
allbut(
extend(
join(orders, discount_rules),
discount: ->{ instance_exec(&rule) } ),
[:rule]
)
end
puts rel
# +------+--------+---------+-----------+
# | :oid | :city | :amount | :discount |
# +------+--------+---------+-----------+
# | O1 | London | 100.000 | 20.000 |
# | O2 | Paris | 100.000 | 15.000 |
# +------+--------+---------+-----------+
Version data entries
8 entries across 8 versions & 1 rubygems