Materialized query tables are useful for complex queries that run on large amounts of data. Db2 can precompute all or part of such queries and use the precomputed, or materialized, results to answer the queries
http://www.csa.ru/dblab/DB2/db2m0/sql0400.htm SQL0437W Performance of this complex query may be sub-optimal. Reason code: "<reason-code>". Cause: The statement may achieve sub-optimal performance since the complexity of the query requires resources that are not available or optimization bou...
20 DB2 UDB Exploitation of the Windows Environment The optimizer incorporates a very sophisticated query rewrite phase that automatically transforms a complex query into a simpler query that is easy to optimize. As a result, the end user will realize the best possible performance regardless of the ...
Complex, multidimensional queries are involved. Currency requirements demand point-in-time consistency, such as at the close of business. 8 DB2 II: Performance Monitoring, Tuning and Capacity Planning Guide 1.3.2 Distributed access (federation) Very simply, federation takes a query in one location ...
DB2 Tutorial website provides you with a comprehensive IBM Db2 tutorial that allows you to master DB2 quickly with many hands-on examples.
Determining what indexes to create is very helpful, but the more challenging aspects of SQL tuning is to make sure that SQL statements are optimally structured/designed and that the query optimizer is choosing the best possible execution plan. This is especially true for complex SQL statements. ...
The expression is more complex than a single host variable with explicit casts The target column has data type of structured type DEFAULT The default value assigned to the column. DEFAULT can be specified only for columns that have a default value. For information about default values of data ...
All 4 databases allow you to have multiple table expressions within one WITH clause anda RECURSIVE CTE expression can have both recursive and non-recursive CTEs. This makes writing complex queries especially where you have the same expressions used multiple times in the query, a lot easier to deb...
Quickly locate the primary key and/or foreign key in DDL scripts to figure out the complex relationship among the various tables. Extracted table, attribute names, data types can be used to generate the CRUD-Statements. Query parse tree in XML Parsing SQL is a notoriously difficult task, but...
Number of expected long-running complex queries Dynamic SQL in the Siebel Application Traditional applications are typically based on static, hard-coded SQL. However, Siebel Business Applications generate dynamic SQL statements at run time, using the Siebel Application Object Manager and the progra...