Oracle Archives - Page 20 of 31

Tuning Distributed Queries in Oracle

When distributed queries can’t be avoided, use IN clauses, set operators such as UNION and MINUS, and use everything else you can to reduce the network traffic between database nodes. Learn more.

Best Uses for the Oracle Bitmap Join Index

This article exanmies three excellent uses for bitmap join indexes in Oracle: on columns other than the join; on multiple columns; and on multiple tables.

Understanding Three-table Joins in Oracle

In a three-table join, Oracle joins two of the tables and joins the result with the third table. Learn how Oracle determines which is the driving table in a query.

Understanding Oracle INDEX-MERGE Joins

Unlike Oracle fast full scans that have a single index satisfying the entire query, INDEX-MERGE joins have multiple indexes satisfying the entire query. Learn how this impacts performance.

Understanding Oracle HASH Joins

HASH joins in Oracle can be effective when the lack of a useful index renders NESTED LOOPS joins inefficient. Learn more.

Understanding Oracle CLUSTER Joins

If two row sources being joined are actually tables that are part of a cluster, and if the join is an equijoin between the cluster keys of the two tables, then Oracle can use a CLUSTER join. Learn more.

Understanding Oracle SORT-MERGE Joins

In a SORT-MERGE join, Oracle sorts the first row source by its join columns, sorts the second row source by its join columns, and then merges the sorted row sources together. Learn more.

Understanding When Oracle Nested Loop Joins Are Ideal

NESTED LOOPS joins in Oracle are ideal when the driving row source is small and the joined columns of the inner row source are uniquely indexed or have a highly selective nonunique index. Learn more.

Five Questions to Ask Before Tackling Oracle Join Issues

There are five primary join methods in Oracle, each with a unique set of features and limitations. Answer these 5 questions before you attack a potential join issue.