What is a covering index A covering index is an index which satisfies all the columns being used in a query without performing a further lookup either to the clustered index or to the base table. It contains all the columns whether they are used in SELECT, JOIN, WHERE, GROUP BY, or ORDER BY clause of the […]
Today, we are going to learn how we can create index on a computed column which improves the performance of SELECT queries. To create a computed column, we will use an user defined function instead of inline code. Also to know about computed columns, refer my previous blog post “What is Computed Column in sql server“. Create index
One of my colleague asked me a question that “Can we create a primary key without a clustered index?”. I answered him that “Yes, of-course!” and also did not forget to share this information to all of you in this post named “Create nonclustered primary key”. I know many of us are well aware of
Lets explore the topic “Index Join in sql server” starting with “what is index join?”. Index join is a technique which uses an index intersection with two or more indexes to fulfill a query completely. If a table has multiple small index instead of a large covering index, the optimizer can choose index intersection on these
What is Bookmark Lookup? If all the columns required by the query are not available in the nonclustered index itself, a lookup is required to base table to pick those columns which are not part of the nonclustered index being used to retrieve the data. Lookup fetches the corresponding data row from the table by
In this topic we are going to compare clustered indexes with nonclustered indexes with their usage and performance and will also discuss some points regarding the topic “when to choose which one”. Clustered Vs NonClustered indexes is an old topic and you can get many article written so far. But in this post I will cover the definitions, structure of
Clustered Vs NonClustered indexes (When to choose which one) Read More »
Rebuild indexes dynamically for all databases In this article we are going to learn how we can rebuild indexes for all the databases having fragmentation level more than defined level. Fragmentation level to rebuild the indexes may vary databases to database and In our example we are assuming it as 20%. Which can be suitable for most database
