Teradata Parallel Data Pump

Chapter 3: Teradata TPump Commands
UPDATE Statement and Atomic Upsert
.IMPORT INFILE Infilename LAYOUT Layoutname APPLY DMLlabelname;
.END LOAD;
Usage Notes - Atomic Upsert
The syntax for Atomic upsert consists of an UPDATE statement and an INSERT statement
separated by an ELSE keyword as follows:
UPDATE ELSE INSERT ;
Teradata TPump inserts the ELSE keyword between the UPDATE and INSERT statements by
itself, so the user should not enter it in the script. If the ELSE keyword is used in this context,
Teradata TPump will terminate with a syntax error.
The and are operands for regular UPDATE and
INSERT SQL statements, respectively. Only certain types of UPDATE and INSERT operands
are valid in an Atomic upsert statement, and the operand parameters within a given upsert
statement are subject to further constraints linking the update and insert parameters.
When using the standard upsert feature, the primary index should always be fully specified for
the UPDATE statement, just as for other DML in a Teradata TPump script, so that the update
can be processed as a one-AMP rather than an all-AMP operation. In addition, both the
UPDATE and the INSERT of an upsert statement pair should specify the same target table,
and the primary index value specified in the UPDATE's WHERE clause should match the
primary index value implied by the column values in the INSERT. When processing an
Atomic upsert statement, Teradata Database will usually reject statements that fail to meet
these basic upsert constraints and return an error, enabling Teradata TPump to detect and
handle constraint violations.
Constraints considered to be basic to the upsert operation are:
• SAME TABLE: The UPDATE and INSERT statements must specify the same table.
• SAME ROW: The UPDATE and INSERT statements must specify the same row; that is, the
primary index value in the inserted row must be the same as the primary value in the
targeted UPDATE row.
• HASHED ROW ACCESS: The UPDATE must fully specify the primary index, allowing the
target row to be accessed with a one-AMP hashed operation.
• Some of these restrictions concern syntax that is supported in UPDATE and INSERT
statements separately but not when combined in an Atomic upsert statement. Restrictions
not supported by the Atomic upsert feature that return an error if submitted to Teradata
Database are:
• INSERT... SELECT: Syntax not supported. The INSERT may not use a subquery to specify
any of the inserted values. Note that support of this syntax is likely to be linked to support
of subqueries in the UPDATE's WHERE clause constraints as described above, and may
involve new syntax features to allow the UPDATE and INSERT to effectively reference the
same subquery.
• UPDATE-WHERE-CURRENT: Syntax not supported. The WHERE clause cannot use an
updatable cursor to do what is called a positioned UPDATE. (It is unlikely that this syntax
will ever be supported.) Note that this restriction does not prevent cursors from being
190 Teradata Parallel Data Pump Reference