exclude

Ruby

rel.exclude(Predicate.eq(:a, "foo"))
rel.exclude(a: "foo", b: "bar", ...)
rel.exclude(->(t) { t[:a] == "foo" })

TypeScript

rel.exclude({ a: "foo" })
rel.exclude({ a: "foo", b: "bar" })
rel.exclude(t => t.a === "foo")

Problem

Remove tuples from a relation that match a given criterion.

Example: Which products are NOT discontinued?

Description

The exclude operator is the inverse of restrict. While restrict keeps tuples that match the predicate, exclude removes them.

exclude(predicate) is equivalent to restrict(NOT predicate).

Ruby

Predicates can be specified as Predicate objects (e.g., Predicate.eq(:status, "inactive")), a hash for equality matching (e.g., { status: "inactive" }), or a lambda that returns true for tuples to exclude.

TypeScript

Predicates can be specified as an object with attribute-value pairs for equality matching ({ status: "inactive" }) or a function that receives a tuple and returns a boolean (t => t.status === "inactive").

Requirements

The specified attributes referenced by the predicate must be part of the input relation’s heading.

Examples

Consult the Overview page for the data model used in these examples.

Basic exclude

Ruby

# Get all suppliers except those in Paris
suppliers.exclude(city: "Paris").to_a

=>
[{:sid=>"S1", :name=>"Smith", :status=>20, :city=>"London"},
 {:sid=>"S4", :name=>"Clark", :status=>20, :city=>"London"},
 {:sid=>"S5", :name=>"Adams", :status=>30, :city=>"Athens"}]

TypeScript

// Get all suppliers except those in Paris
suppliers.exclude({ city: "Paris" }).toArray()

// =>
// [{ sid: "S1", name: "Smith", status: 20, city: "London" },
//  { sid: "S4", name: "Clark", status: 20, city: "London" },
//  { sid: "S5", name: "Adams", status: 30, city: "Athens" }]

With function predicate

Ruby

# Exclude suppliers with status >= 30
suppliers.exclude(->(t) { t[:status] >= 30 }).to_a

=>
[{:sid=>"S1", :name=>"Smith", :status=>20, :city=>"London"},
 {:sid=>"S2", :name=>"Jones", :status=>10, :city=>"Paris"},
 {:sid=>"S4", :name=>"Clark", :status=>20, :city=>"London"}]

TypeScript

// Exclude suppliers with status >= 30
suppliers.exclude(t => t.status >= 30).toArray()

// =>
// [{ sid: "S1", name: "Smith", status: 20, city: "London" },
//  { sid: "S2", name: "Jones", status: 10, city: "Paris" },
//  { sid: "S4", name: "Clark", status: 20, city: "London" }]

Comparison with restrict

exclude and restrict are complementary operations:

Ruby

# These produce the same result:
suppliers.exclude(city: "Paris")
suppliers.restrict(Predicate.neq(:city, "Paris"))

# Together they partition the relation:
paris = suppliers.restrict(city: "Paris")
not_paris = suppliers.exclude(city: "Paris")
# paris.union(not_paris) equals suppliers

TypeScript

// These produce the same result:
suppliers.exclude({ city: "Paris" })
suppliers.restrict(t => t.city !== "Paris")

// Together they partition the relation:
const paris = suppliers.restrict({ city: "Paris" })
const notParis = suppliers.exclude({ city: "Paris" })
// paris.union(notParis) equals suppliers