Database index(sql server)

SQL SERVER INDEXJAJA

TOPIC

• WHAT IS THE INDEX OF DATABASE SYSTEM• CLUSTERED INDEX VS. NONCLUSTERED INDEX• THE STATISTICS OF INDEX• THE COVERAGE IDNEX• WHAT IS INDEX FRAGMENTATION• CREATE THE RIGHT INDEX

WHAT IS THE INDEX OF DATABASE SYSTEM

I want to query customer BIG-Data

…5 min …10 min

…30 min…20 min

BEFORE AFTER

INDEX IS DECIDED DATA STORAGE STRUCTURE

HAS CLUSTERED INDEXNO INDEX

CLUSTERED INDEX VS. NONCLUSTERED INDEXCLUSTERED INDEX NONCLUSTERED INDEX

CL01 Taipei Ken

WHERE Country=‘Taipei’

Got it CL Key value CL01

Searching …

Binary Search Tree (BST)

http://visualgo.net/bst.html

CLUSTERED AND NONCLUSTERED INDEXBASE ON B-TREE

ANYTHING IS A DOUBLE-EDGED SWORDRECORD

INDEX-01

Page-01

INDEX-02 RECORD001PG01-RECORD001 PG01-RECORD001

RECORD002PG01-RECORD002 PG01-RECORD002

BE CAREFUL INCREASE THE INDEX

THE STATISTICS OF INDEX

IT’S IMPORTANT FOR SQL TO GUESS YOUR QUERY RESULT NUMBER

DEMO

THE COVERAGE IDNEX

INCLUDE EVERYTHING YOU USEDSELECT COLUMN

JOIN COLUMN

WHERE CONDITION COLUMN

DEMO

WHAT IS INDEX FRAGMENTATION

DEMO

CREATE THE RIGHT INDEX

PRINCIPLEFREQUENTLY USED COLUMNS

COLUMN UNIQUENESS

COLUMN DATA TYPE