Ubuntu Unleashed 2013 Edition: Covering 12.10 and 13.04, Eighth Edition

Query Optimization

The biggest speed-ups can be seen by reprogramming your SQL statements so they are more efficient. If you follow these tips, your server will thank you:

• Select as little data as possible. Rather than SELECT *, select only the fields you need.

• If you need only a few rows, use LIMIT to select the number you need.

• Declare fields as NOT NULL when creating tables to save space and increase speed.

• Provide default values for fields and use them where you can.

• Be very careful with table joins because they are the easiest way to write inefficient queries.

• If you must use joins, be sure you join on fields that are indexed. They should also preferably be integer fields because these are faster than strings for comparisons. ...