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Virtual Columns has been introduced in Oracle Database 11g Release 1. Here is a good tutorial I could find from Oracle-Base website. The link for the tutorial is at the bottom of this article. - Anantha When queried, virtual columns appear to be normal table columns, but their values are derived rather than being stored on disc. The syntax for defining a virtual column is listed below. column_name [datatype] [GENERATED ALWAYS] AS (expression) [VIRTUAL] If the datatype is omitted, it is determined based on the result of the expression. The GENERATED ALWAYS and VIRTUAL keywords are provided for clarity only. The script below creates and populates an employees table with two levels of commission. It includes two virtual columns to display the commission-based salary. The first uses the most abbreviated syntax while the second uses the most verbose form. CREATE TABLE employees (  id          NUMBER,  first_name  VARCHAR...

Creating or Rebuilding Indexes Online: Online Index Rebuilds allows you to perform DML operations on the base table during index creation. You can use the CREATE INDEX ONLINE and DROP INDEX ONLINE statements to create and drop an index in an online environment. During index build you can use the CREATE INDEX ONLINE to create an index without placing an exclusive lock over the table. CREATE INDEX ONLINE statement can speed up the creation as it works even when reads or updates are happening on the table. The ALTER INDEX REBUILD ONLINE can be used to rebuild the index, resuming failed operations, performing batch DML, adding stop words to index or for optimizing the index. The CREATE INDEX ONLINE and ALTER INDEX REBUILD ONLINE options have been there for a long time to easy the task of online index rebuilding. However in highly active they still can introduce locking issues. Table Locks: A table lock is required on the index base table at the start of the CREATE or REBUILD process to...