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blank=True vs null=True in Django

  • null=True

    • Database layer.
    • Column accepts SQL NULL.
    • Django represents the absence of a value as Python None.
    • Needed for non-string fields (e.g., DateField, ForeignKey) to store "no value."
    • Indexes and unique constraints treat NULL as distinct from every non-null value.

  • blank=True

    • Validation layer.
    • Model and form validation permit an empty value on save or submit.
    • For strings, the actual value stored is '' (empty string) unless null=True is also set.
    • Has no effect on the SQL schema.

  • Common patterns

    • String fields: blank=True, null=False → empty string stored, forms omit value.
    • Non-string fields: blank=True, null=True → database NULL used, validation allows omission.
    • Mixing null=True, blank=False rarely useful--database allows NULL, but validation rejects empty input.
    • Leaving both as False enforces mandatory data at both database and validation levels.

  • Key distinctions

    • null controls storage; blank controls validation.
    • Database NULL ≠ empty string; choose one to avoid ambiguity.