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SQL Performance

Last updated: September 26, 2016

What Does SQL Performance Mean?

SQL performance is measured by how efficiently and quickly SQL queries are able to perform the required function. SQL performance can be measured by the time it takes to complete the operation and whether the output of the operation matches the expected requirements. SQL performance can drop below a certain standard due to various reasons, but there are ways to improve performance.


Techopedia Explains SQL Performance

SQL can perform both simple and complex operations. An example of a simple operation can be retrieving the dates of birth of all employees in a certain department, while that of a complex operation can be retrieving the dates of birth of all employees in a large enterprise whose names end with the letter P, who have passport numbers starting with 54 and have traveled outside the United States in the last 15 years. The more complex the operation, the longer the amount time needed.

There are many ways to improve SQL performance, including:

  • Multiple joins in a single query should be avoided.
  • A set-based query should be used instead of a cursor-based query.
  • Non-correlated scalar sub-queries should be avoided in standard queries.
  • Multi-statement Table Valued Functions (TVFs) should be avoided as part of the query.
  • Indexes should be used as efficiently as possible.
  • The columns in an index should be positioned carefully.

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