Updating xml column sql server 2016

04-Nov-2019 23:30

The selection of the right indexes for a database and its workload is a complex balancing act between query speed and update cost.

Narrow indexes, or indexes with few columns in the index key, require less disk space and maintenance overhead.

The query optimizer in SQL Server reliably chooses the most effective index in the vast majority of cases.

Your overall index design strategy should provide a variety of indexes for the query optimizer to choose from and trust it to make the right decision.

An index contains keys built from one or more columns in the table or view.

These keys are stored in a structure (B-tree) that enables SQL Server to find the row or rows associated with the key values quickly and efficiently.

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Also, you can determine the index storage location by using filegroups or partition schemes to optimize performance.

In reality, an incorrect index choice can cause less than optimal performance.

Therefore, the task of the query optimizer is to select an index, or combination of indexes, only when it will improve performance, and to avoid indexed retrieval when it will hinder performance.

However, you can do the following: By creating the nonclustered index on a different filegroup, you can achieve performance gains if the filegroups are using different physical drives with their own controllers. Because you cannot predict what type of access will occur and when it will occur, it could be a better decision to spread your tables and indexes across all filegroups.

Data and index information can then be read in parallel by the multiple disk heads. This would guarantee that all disks are being accessed because all data and indexes are spread evenly across all disks, regardless of which way the data is accessed.

Experienced database administrators can design a good set of indexes, but this task is very complex, time-consuming, and error-prone even for moderately complex databases and workloads.