Represents a runtime database lookup to get a field value from an existing record.

Unlike belongs_to which syncs a fixture module, lookup queries the database directly for an existing record.

Simple lookup by key/value

# Get country.id where code = "NO"
country_id: Sow.lookup(MyApp.Country, :code, "NO")

Lookup with custom field extraction

# Get country.name instead of country.id
country_name: Sow.lookup(MyApp.Country, :code, "NO", field: :name)

Lookup with multiple match criteria

# Get organization.id where country_id and name match
org_id: Sow.lookup(MyApp.Organization, %{country_id: 1, name: "ACME"})

Chained lookups

# Nested lookup - resolve country_id first, then find organization
org_id: Sow.lookup(MyApp.Organization, %{
  country_id: Sow.lookup(MyApp.Country, :code, "NO"),
  name: "ACME"
})