Inserting When Using a DEFAULT Function
The following rules apply when using a DEFAULT function to insert rows into a table:
The DEFAULT function takes a single argument that identifies a relation column by
name. The function evaluates to a value equal to the current default value for the
column. For cases where the default value of the column is specified as a current
built‑in system function, the DEFAULT function evaluates to the current value of system
variables at the time the request is executed.
The resulting data type of the DEFAULT function is the data type of the constant or
built-in function specified as the default unless the default is NULL. If the default
is NULL, the resulting date type of the DEFAULT function is the same as the data type
of the column or expression for which the default is being requested.
The DEFAULT function has two forms. It can be specified as DEFAULT
or DEFAULT (
column_name)
. When no column name is specified, the system derives the column based on context.
If the column context cannot be derived, the request aborts and an error is returned
to the requestor.
The DEFAULT function without a column name can be specified in the expression list.
If the INSERT request has a column list specified, the column name for the DEFAULT
function is the column in the corresponding position of the column list. If the request
does not have a column name list, the column name is derived from the position in
the VALUES list.
The DEFAULT function without a column name in the INSERT request cannot be a part
of an expression; it must be specified as a standalone element. This form of usage
is ANSI compliant.
The DEFAULT function with a column name can be specified in an expression list. This
is a Teradata extension to ANSI.
The DEFAULT function with a column name can be specified anywhere in the expression.
This is a Teradata extension.
When there is no explicit default value associated with the column, the DEFAULT function
evaluates to null.
For more information about the DEFAULT function, see SQL Functions, Operators, Expressions, and Predicates.