March 2012
Intermediate to advanced
442 pages
9h 31m
English
Content preview from IBM DB2 9.7 Advanced Application Developer CookbookBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Implementing hierarchical queries for recursion support
The hierarchical query is a new type of SQL statement in DB2 9.7, which enables the retrieval of the hierarchical data. One can enable this feature by setting the DB2_COMPATIBILITY_VECTOR registry variable to ORA.
We can build the hierarchical queries by using the CONNECT BY clause, pseudo columns such as LEVEL, unary operators such as CONNECT_BY_ROOT and PRIOR, and using a new scalar function, SYS_CONNECT_BY_PATH.
Getting ready
We will run though CONNECT BY, LEVEL, CONNECT_BY_ROOT, and PRIOR to see how easy it is to get the hierarchical data in DB 9.7
How to do it...
If a database table contains hierarchical data, then we can use hierarchical queries to extract the data in a hierarchical order. ...
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