Nothing brings a server to its knees more quickly than a poorly written, memory gobbling, runaway #SQL query. Here are some best practices for writing SQL queries:
Use consistent formatting: Consistent formatting makes SQL code easier to read and understand. Use a consistent indentation style, capitalization, and line breaks to improve readability.
Use meaningful table and column names: Use descriptive and meaningful table and column names that accurately represent the data they contain. Avoid using abbreviations or acronyms that may be confusing to others.
Use aliases for table and column names: Use aliases for table and column names to simplify long or complex queries. Aliases can also make queries easier to read and understand.
Avoid using SELECT *: Avoid using SELECT * in SQL queries, as it can have performance implications and may return unnecessary data. Instead, explicitly list the columns that are needed in the SELECT statement.
Use JOINs appropriately: Use JOINs to combine data from multiple tables, but use them appropriately. Use the appropriate type of JOIN (INNER JOIN, LEFT JOIN, RIGHT JOIN, etc.) and ensure that the join conditions are correct.
Use WHERE clauses for filtering: Use WHERE clauses to filter data based on specific criteria. This can improve query performance by reducing the amount of data that needs to be processed.
Use GROUP BY and HAVING clauses for aggregation: Use GROUP BY clauses to group data by one or more columns and use HAVING clauses to filter groups based on specific criteria. This can be useful for performing aggregation functions such as SUM, COUNT, and AVG.
Use subqueries when appropriate: Use subqueries to perform complex queries that cannot be accomplished with a single query. This can improve query performance and simplify complex queries.
Use indexes for performance: Use indexes on columns that are frequently used in WHERE clauses or JOIN conditions. This can improve query performance by reducing the amount of data that needs to be scanned.
Test queries before running them in production: Always test SQL queries in a non-production environment before running them in production. This can help identify performance issues, syntax errors, or unexpected results.
By following these SQL query best practices, you can improve the readability, maintainability, and performance of your SQL queries for overall happy server performance.