DATABASE & SQL/PLSQL
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INDEXES
An Indexes is:
- SQL server used an internal table structure that provide quick access to rows of a table>
- It is totally based on the values of one or more columns
- SQL Server indexes are like the indexes at the back of a book, which help in locating content
Advantage Of Using Indexes
- The primary purpose of an index is to provide faster
access to data pages
- When server searched anything, it searching the
index at the place of searching the whole page
- Server scan the index and get the address of data
storage location and directly access the information
- Indexes are also used as a mechanism of enforcing
data uniqueness
- An index speeds up the processing of queries that
use joins or other clauses like ORDER BY or GROUP BY, by allowing to faster
access of data
- Improve the speed of the execution of queries
- Enforce uniqueness of data
- Speed up joins between table
Disadvantage Of Using Indexes
- Indexes does not indexing every column of the table
- It takes time to create index>
- Each index create requires space to store data along
with the original data source-the table
- An index gets updated each time the data is modified
Types Of INDEXES
- CLUSTERED Index
- NONCLUSTERED Index
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