Tips to increase query efficiency

In general, we can speed up queries by changing it so that it

• Reads fewer rows
• Avoids a sort, sorts fewer rows, or sorts on a simpler key
• Reads rows sequentially rather than non-sequentially

• Filter is the term used for conditions in the WHERE clause.
• Importance of table order in the from clause of a select statement with filters. Tables with filters should appear first.
• Rewrite a join through views.
• Do not sort if the sort key (or any part of it) is not indexed.
• Provide indexes for join attributes
• Use UNION instead of OR condition
• Rebuild indexes after many updates
• Avoid correlated subqueries
• Avoid difficult regular expressions in the LIKE operation
• Use temporary tables to speed queries