INDEXING IN ORACLE DATABASE
A BRIEF INTRO ON INDEX: Just like a book index helps us in finding the chapter and page number, an oracle index speeds up access time to the rows. Indexes are optional structures associated with tables. An index is also a schema object. We can drop an index without dropping the table it indexes. An index can be created explicitly or automatically. When we drop a table the corresponding indexes of the table are dropped. A unique index gets created when we create a unique key or primary key in a table definition. The name of the index is the name of the constraint. Indexes can be unique or non-unique. Unique indexes guarantee that no two rows of a table have duplicate values in the columns that define the index. Non-unique indexes do not impose this restriction on the column values. The presences of more number of indexes on a table decreases the performance of DML statements, because Oracle must make changes to the indexes associated with the table For more c...