Sybase 12.4.2 - Manual (Page 6)

Contents
vi
Deleting views ....................................................................... 131
Views in the system tables .................................................... 131
Working with indexes ................................................................... 132
Introduction to indexes .......................................................... 132
Creating indexes ................................................................... 133
Indexes in the system tables ................................................. 133
Removing indexes................................................................. 134
CHAPTER 4 Adaptive Server IQ Indexes ........................................................ 135
Overview of indexes ..................................................................... 135
Adaptive Server IQ index types............................................. 135
Benefits over traditional indexes ........................................... 137
Creating Adaptive Server IQ indexes ........................................... 138
The CREATE INDEX statement............................................ 138
Creating an index with Sybase Central ................................. 139
Creating indexes concurrently............................................... 139
Choosing an index type................................................................ 140
Number of unique values in the index ................................... 141
Types of queries.................................................................... 141
Indexing criteria: disk space usage ....................................... 143
Data types in the index.......................................................... 143
Combining index types .......................................................... 144
Adaptive Server IQ index types.................................................... 144
Default column index............................................................. 145
The Low_Fast (LF) index type............................................... 145
The High_Group (HG) index type.......................................... 146
The High_Non_Group (HNG) index type .............................. 148
Optimizing performance for ad hoc joins............................... 149
Selecting an index ................................................................. 150
Adding column indexes after inserting data ................................. 151
Using join indexes ........................................................................ 151
Join indexes improve query performance ............................. 151
How join indexes are used for queries .................................. 152
Relationships in join indexes ................................................. 152
When a join becomes ad hoc ................................................ 152
Join hierarchy overview......................................................... 152
Columns in the join index ...................................................... 153
The join hierarchy in query resolution ................................... 154
Multiple table joins and performance..................................... 156
Steps in creating a join index ................................................ 157
Synchronizing join indexes.................................................... 158
Defining join relationships between tables ............................ 159
Issuing the CREATE JOIN INDEX statement ....................... 162
Creating a join index in Sybase Central ................................ 164