• 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