Class CheckConstraint

lib/sqlalchemy/sql/schema.py:4855–4963

A table- or column-level CHECK constraint. Can be included in the definition of a Table or Column.

class CheckConstraint(ColumnCollectionConstraint):
    """A table- or column-level CHECK constraint.

    Can be included in the definition of a Table or Column.
    """

    _allow_multiple_tables = True

    __visit_name__ = "table_or_column_check_constraint"

    @_document_text_coercion(
        "sqltext",
        ":class:`.CheckConstraint`",
        ":paramref:`.CheckConstraint.sqltext`",
    )
    def __init__(
        self,
        sqltext: _TextCoercedExpressionArgument[Any],
        name: _ConstraintNameArgument = None,
        deferrable: Optional[bool] = None,
        initially: Optional[str] = None,
        table: Optional[Table] = None,
        info: Optional[_InfoType] = None,
        _create_rule: Optional[Any] = None,
        _autoattach: bool = True,
        _type_bound: bool = False,
        **dialect_kw: Any,
    ) -> None:
        r"""Construct a CHECK constraint.

        :param sqltext:
         A string containing the constraint definition, which will be used
         verbatim, or a SQL expression construct.   If given as a string,
         the object is converted to a :func:`_expression.text` object.
         If the textual
         string includes a colon character, escape this using a backslash::

           CheckConstraint(r"foo ~ E'a(?\:b|c)d")

        :param name:
          Optional, the in-database name of the constraint.

        :param deferrable:
          Optional bool.  If set, emit DEFERRABLE or NOT DEFERRABLE when
          issuing DDL for this constraint.

        :param initially:
          Optional string.  If set, emit INITIALLY <value> when issuing DDL
          for this constraint.

        :param info: Optional data dictionary which will be populated into the
            :attr:`.SchemaItem.info` attribute of this object.

        """

        self.sqltext = coercions.expect(roles.DDLExpressionRole, sqltext)
        columns: List[Column[Any]] = []
        visitors.traverse(self.sqltext, {}, {"column": columns.append})