Category: SQL


Understanding Function Based Index In Oracle Database

Traditionally, performing a function on an indexed column in the where clause of a query guaranteed an index would not…


Understanding Reverse Key Index In Oracle Database

Reverse B-TREE key indexes reverses the bytes of the key value in the index to reduce Index block contention. Index…


Understanding Bitmap Index in Oracle database

BITMAP index are different from B-TREE index in the manner they store data. • B-TREE index stores data in tree…


Understanding Materialized View ON PREBUILT TABLE

The “ON PREBUILT TABLE” clause is used when you have already created a replicated table using “CTAS” and now want…


Understanding DML Statements on a SQL Join View

A join view is a view based on a join. Special considerations apply when you issue a DML(INSERT, UPDATE, or…


Understanding Oracle SYS_CONTEXT

The SYS_CONTEXT function is used in both SQL & PL/SQL to return information about the Oracle environment that you’re working…


Understanding Oracle External Tables

External tables are read-only tables that allow Oracle to query data that is stored outside the database in flat files….


Understanding Join Methods In Oracle Database 19c

A join method is the mechanism for joining two row sources. Depending on the statistics, the optimizer chooses the method…


Understanding Clustering In Oracle Database

Clustering is a method of storing tables that are intimately related and often joined together into the same area on…


Understanding RealTime Materialized View In Oracle Database 19c

In earlier Oracle version, QUERY REWRITE feature used to stop working as soon as the materialized view become STALE, unless…