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constraint(table, name, opts \\ [])

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Defines a constraint (either a check constraint or an exclusion constraint) to be evaluated by the database when a row is inserted or updated.


create constraint("users", :price_must_be_positive, check: "price > 0")
create constraint("size_ranges", :no_overlap, exclude: ~s|gist (int4range("from", "to", '[]') WITH &&)|)
drop   constraint("products", "price_must_be_positive")


  • :check - A check constraint expression. Required when creating a check constraint.
  • :exclude - An exclusion constraint expression. Required when creating an exclusion constraint.
  • :prefix - The prefix for the table.
  • :validate - Whether or not to validate the constraint on creation (true by default). Only available in PostgreSQL, and should be followed by a command to validate the new constraint in a following migration if false.