Indexes in Databases || Why Index needed in Database
Channel: Data Science Center
Date: 19/04/2021

Indexes in Databases
to improve the performance of any query 

index is a database object
creation of indexes Method:
Automatically
PRIMAY KEY, Unique constraint to any coulumn 

MANUALLY

Creation of Index:

CREATE [UNIQUE][BITMAP] INDEX indx_name
on Table_name(column_name);

When create index:

WIDE RANGE OF VALUE IN A COLUMN
May contains large number of NULL Value. 
frequently access WHERE Clause or Join
less than 2% of the rows in the table

When Not create index:
i. column not use in condition than no need to create index 
ii. more than 4% of data, 
iii. when table is updated very frequiently 

Advantages: 
Improve Performance
 Disadvantages:
 Extra store space 

Remove the index:

Drop index index_name;