![]() When a domain has multiple CHECK constraints, they will be tested in alphabetical order by name. If the expression produces a FALSE result, an error is reported and the value is not allowed to be converted to the domain type.Ĭurrently, CHECK expressions cannot contain subqueries nor refer to variables other than VALUE. Expressions evaluating to TRUE or UNKNOWN succeed. It should use the key word VALUE to refer to the value being tested. Each constraint must be an expression producing a Boolean result. CHECK ( expression)ĬHECK clauses specify integrity constraints or tests which values of the domain must satisfy. Its use is discouraged in new applications. This clause is only intended for compatibility with nonstandard SQL databases. Values of this domain are allowed to be null. Values of this domain are prevented from being null (but see notes below). ![]() If not specified, the system generates a name. CONSTRAINT constraint_nameĪn optional name for a constraint. In turn, the domain default overrides any default value associated with the underlying data type. If a default value is defined for a particular column, it overrides any default associated with the domain. The default expression will be used in any insert operation that does not specify a value for the column. If no default value is specified, then the default value is the null value. The data type of the default expression must match the data type of the domain. The value is any variable-free expression (but subqueries are not allowed). The DEFAULT clause specifies a default value for columns of the domain data type. The underlying type must be collatable if COLLATE is specified. ![]() If no collation is specified, the domain has the same collation behavior as its underlying data type. collationĪn optional collation for the domain. The name (optionally schema-qualified) of a domain to be created. ![]()
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