What are your most common sql optimizations?

Question

What are your most common SQL optimization that you used?

Answer 1

The best optimisation I've ever had using SQL was to really understand what was needed to be done the data and REMOVE ton's of SQL from the query.

The fastest query is the query that does not have to be run.

REALLY THINK about what your doing to the data. Are you working row-by-row? (then use set based code).

• Do you really need to join to all those tables?

• Can two small (simple) queries do the job better and quicker than a single large query?

• If you combine these two queries into a single query can it run faster?

Finally, PROFILE your queries (EXPLAIN PLAN or SQL PROFILER) and look at the "IO gets". Generally you want to reduce the number of GET's to a ratio something like 10 gets per output row.