How do you optimize a SQL query?

It’s vital you optimize your queries for minimum impact on database performance.

  1. Define business requirements first.
  2. SELECT fields instead of using SELECT *
  3. Avoid SELECT DISTINCT.
  4. Create joins with INNER JOIN (not WHERE)
  5. Use WHERE instead of HAVING to define filters.
  6. Use wildcards at the end of a phrase only.

How can improve query performance in SQL Server?

How Can You Select Which Queries to Optimize?

  1. Consistently Slow Queries.
  2. Occasionally Slow Queries.
  3. Queries With Red Flags.
  4. Queries That Majorly Contribute to Total Execution Time.
  5. Define Your Requirements.
  6. Reduce Table Size.
  7. Simplify Joins.
  8. Use SELECT Fields FROM Instead of SELECT * FROM.

What are the best practices to improve query performance of databases?

Our 6 Best Practices for Improving SQL Query Performance

  1. Tune queries. A great feature of the SQL language is that it is fairly easy to learn and to use in creating commands.
  2. Add memory.
  3. Perform index maintenance.
  4. Add extra spindles or flash drives.
  5. Optimize the I/O subsystem.
  6. Use DymaxIO fast data software.

How do I optimize SQL query to run faster?

How To Speed Up SQL Queries

  1. Use column names instead of SELECT *
  2. Avoid Nested Queries & Views.
  3. Use IN predicate while querying Indexed columns.
  4. Do pre-staging.
  5. Use temp tables.
  6. Use CASE instead of UPDATE.
  7. Avoid using GUID.
  8. Avoid using OR in JOINS.

What are the different query optimization techniques?

There are two methods of query optimization.

  • Cost based Optimization (Physical) This is based on the cost of the query. The query can use different paths based on indexes, constraints, sorting methods etc.
  • Heuristic Optimization (Logical) This method is also known as rule based optimization.

How can I speed up my large table queries?

  1. Instead of UPDATE, use CASE. In the SQL query, an UPDATE statement writes longer to a table than a CASE statement, because of its logging.
  2. Reduce nested views to reduce lags.
  3. Data pre-staging.
  4. Use temp tables.
  5. Avoid using re-use code.
  6. Avoid negative searches.
  7. Avoid cursors.
  8. Use only the correct number of columns you need.

What are the best practices in SQL?

10 Best Practices to Write Readable and Maintainable SQL Code

  1. Use Uppercase for the Keywords.
  2. Use Snake Case for the schemas, tables, columns.
  3. Use aliases when it improves readability.
  4. Formatting: Carefully use Indentation & White spaces.
  5. Avoid Select *
  6. Go for the ANSI-92 JOIN Syntax.
  7. Use Common Table Expression (CTE)

What are the different ways to speed up SQL queries?

Below are 23 rules to make your SQL faster and more efficient

  1. Batch data deletion and updates.
  2. Use automatic partitioning SQL server features.
  3. Convert scalar functions into table-valued functions.
  4. Instead of UPDATE, use CASE.
  5. Reduce nested views to reduce lags.
  6. Data pre-staging.
  7. Use temp tables.
  8. Avoid using re-use code.