IBM Licensed Programs: Database Products 547
IBM Licensed Programs: Database Products
These functions can operate over all global database types, including LOBs and UDTs.
UDFs allow queries to contain powerful computation and search predicates to filter
irrelevant data close to the source of the data. The global SQL optimizer treats global
UDFs exactly like built-in functions, such as SUBSTR and LENGTH.
Recursive Global SQL Queries: DataJoiner supports not only multi-vendor bills-of-material
queries but also the more powerful forms of recursive queries such as path expressions.
Examples of queries that become possible with recursion are:
• Global bills-of-material queries, where a user wants to return subparts of parts, and
subparts of subparts, and so on.
• Global path expression queries, where a user wants to calculate the lowest-cost plane
fares on multi-hop routes. For example, the following query can be formulated using
recursive SQL: Return all possible flights from San Jose to Perth without making a
stopover in London or Chicago and with no more than three plane changes.
The global optimizer function of DB2 DataJoiner is capable of making sophisticated
transformations for multi-vendor recursive queries and nonrecursive queries, resulting in the
selection of better access plans for improved performance.
The combination of global user-defined types and functions can mask the multi-vendor
representation of the data and the definition of a set of functions that interpret the
multi-vendor data. The global types and functions enable the creation of global function
libraries, which can be developed outside of the database and then added to it, thereby
extending database functionality.
Stored Procedures: DB2 DataJoiner now supports the invocation of stored procedures. The
SQL92 level of function for stored procedure calls is supported. Stored procedures can
greatly improve the performance of applications by minimizing network traffic. A stored
procedure is an executable module stored on the database server that is comprised of SQL
statements and application logic that are performed frequently. When a call to a stored
procedure is made, only the instruction to invoke a procedure is passed to the database
server instead of passing individual SQL statements.
DB2 DataJoiner compensates for those data sources that do not support stored procedures.
In these situations, DB2 DataJoiner runs the stored procedure locally and creates the
instructions and SQL necessary for the remote data source to complete the work.
DB2 DataJoiner can be used to invoke stored procedures on database servers that support
them such as DB2 for MVS Version 4 and DB2 for OS/400 Version 3.
DB2 DataJoiner can “cascade” stored procedures. This powerful feature means that a stored
procedure could start on DataJoiner and call another stored procedure on Oracle, which in
turn could cascade others.
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