Rules for Using the DEFAULT Function With MERGE Requests
The following rules apply when using a DEFAULT function within a MERGE request:
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.
You can specify the DEFAULT function as DEFAULT or DEFAULT (column_name). When a column name is not 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.
All the rules listed for the UPDATE statement also apply to the UPDATE in a MERGE
statement. See “Rules for Using the DEFAULT Function With Update” on page 483.
All the rules listed for the INSERT statement also apply to the INSERT in a MERGE
statement. See “Inserting When Using a DEFAULT Function” on page 361.
When the SQL Flagger is enabled, a DEFAULT function specified with a column name argument
for inserts or updates is flagged as a Teradata extension.
For more information about the DEFAULT function, see SQL Functions, Operators, Expressions, and Predicates.