Teradata Parallel Data Pump

Appendix D: User-Defined-Types and User-Defined-Methods
User-Defined-Types and User-Defined-Methods
User-Defined-Methods (UDMs)
Teradata Database developer-created custom functions, which are explicitly connected to
UDTs are known as User-Defined-Methods (UDMs). All UDMs must reside on server.
UDMs can be used to create an interface to the UDT that is independent of the UDT's internal
representation. This makes it possible to later enhance a given UDT even in cases where the
internal representation of the UDT must be changed to support the enhancement, without
changing all of the database applications which use the UDT.
Creating UDTs with Teradata TPump
Teradata TPump cannot create a custom UDT.
Inserting and Retrieving UDTs with Client Products
External Types
A UDT can only exist on the Teradata Database server. Each UDT has an associated “from-sql
routine” and “to-sql routine”.
• Insert - The “to-sql routine” constructs a UDT value from a pre-defined type value. The
“to-sql routine” is automatically invoked when inserting values from a client system into a
UDT on the Teradata Database server.
• Retrieve - The “from-sql routine” generates a pre-defined type value from a UDT. The
“from-sql routine” is automatically invoked when a UDT is retrieved from the Teradata
Database server to a client system.
The “from-sql routine” and the “to-sql routine” create a mapping between a UDT and a predefined
type. This pre-defined type is called the external type of a UDT. A client application
only deals with the external type; it does not deal with UDT value directly.
External Type Example
For example, if the following conditions exist:
• UDT named FULLNAME exists
• The external type associated with FULLNAME is VARCHAR(46)
Then, during an retrieve of FULLNAME values, the Teradata Database server converts the
values from FULLNAME values to VARCHAR(46) values by invoking the “from-sql routine”
associated with the FULLNAME UDT.
Note: The client must expect to receive the data in the same format as it receives
VARCHAR(46) values.
Similarly, when values are provided by the client for insert into a FULLNAME UDT, the client
must provide values in the same way it would provide values for a VARCHAR(46) field. The
Teradata Database server will convert the values from VARCHAR(46) to FULLNAME values
using the “to-sql routine” associated with the FULLNAME UDT.
258 Teradata Parallel Data Pump Reference