In this article we introduce you to the concept of Indexes in Ms SQL Server
In SQL Server, indexes are used to make the task of data access comparatively faster. With the help of indexes, we are able to glance at the entire database file in a single scroll. Like in every book we see an index at the beginning; it makes the presentation of our data more systematic and organized.
Indexes are mostly in the form of tables. They have entries of topics and sub-topics. It works in a chronological manner. A Clustered Index is the one that contains the actual data. A Non Clustered Index acts as a pointer to the data. A table consists of a single Clustered Index, while Non Clustered Indexes can be around 999 in number. An index prevents SQL Server to read through the entire data for resolving a query. Therefore, it provides the client with a much more ordered platform. As data integrity is assured. It avoids mess and confusion. The Task of reaching out to specific portions of data is simplified by indexes. With some simple commands using its accurate syntax arrangement, we can create indexes in no time. We can say that an Index is a kind of Meta information.
Creating indexes have no favorable or unfavorable effect on the data.
How to Create Indexes
- To Begin with, one should use the basic CREATE INDEX statement. This enables the user to allot a name to the index. Two things should be emphasized. One is to specify the order of the index whether ascending or descending.
- To state the table and its columns, the syntax for this command is as follows : CREATE INDEX index_name ON table_name.
- In case the user wants to create an index with a single column, there is a separate command. There is no upper limit for adding columns.
- Another type is the Unique Index: These are oriented towards a better performance. They ensure data consistency and accuracy. They do not allow entry of any incorrect or replicated values into the table.
- There are composite indexes with multiple rows and columns.
- An Index can be dropped by using simple SQL DROP command.
- Indexing is a tireless effort with SQL Server. It has some of its compatible features. One of these is that it allows an opportunity for time to time modification. In other words, we can make alterations, which is to add, delete and modify columns in a particular table.
A SQL Crash can compromise all the indexes created in a SQL Server database
Over a period of time, it is quite logical for database administrators to create a whole set of indexes to improve the performance of the database. However if you encounter a SQL crash, all the data stored in it along with indexes that you have created would be at risk. Now if you are looking to recover your data from a compromised SQL data file in quick time, you need to run a specialized sql server recovery tool like DataNumen SQL Recovery application. This powerful software can instantly draw out all the records stored in the compromised SQL file along with any indexes that you may have created.
Alan Chen is President & Chairman of DataNumen, Inc., which is the world leader in data recovery technologies, including access recovery and sql recovery software products. For more information visit https://www.datanumen.com/