Joining Data from Multiple Tables Best Practices

06 Nov 2010

SQL

Consider the following when you join data from multiple tables:

• Join tables on primary and foreign keys because it improves performance
• Limit the number of tables in a join Limit the number of tables in a join query because too many joins can slow down performance
• Use table aliases
• Use the UNION clause to bring together queries from separate data sources
• Use the EXCEPT clause instead of the NOT EXISTS clause in a subquery to retrieve distinct rows for a table