Any expression that returns a scalar value.
If not specified, the value is assumed to be NULL.
When running in ANSI mode, the default_value_expression data type must match value_expression. An error occurs if the data types do not match.
In Teradata mode, the database attempts to match the default_value_expression data type to value_expression by doing a cast to value_expression data type to execute the query. If there are casting rule violations, Teradata Database displays an error message.