I am now about one year into writing my next book "Oracle SQL Tuning: The Definitive Reference," and I've discovered some fascinating new principles of SQL tuning, counterintuitive approaches that can make your SQL run faster than ever before.
Many experts correctly state that a problem should always be solved using SQL without using PL/SQL unless absolutely necessary, but there is a limit to that technology. Once a SQL query has subqueries nested within subqueries, subqueries in the select clause (a scalar subquery), subqueries in the from clause (an in-line view), the SQL becomes difficult to read, hard to maintain, and challenging to optimize. In these cases, we can use some powerful Oracle tools to divide and conquer complex SQL statements.
Because SQL is a declarative language, we can formulate equivalent queries with numerous techniques. SQL is a "state space" query language where you simply request the desired rows, and there are many ways to write the same query.
In the past, programming competitions were not concerned with who could solve a problem the fastest but with who could write the solution that ran the most efficiently. Today this is no longer the case, and SQL developers are charged with getting the right rows back as quickly as possible, regardless of the internal execution plan or the time required to execute the query!
Follow the link below to take a closer look at several powerful SQL re-writing techniques:
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To pre-order my SQL tuning book, follow the link below where you can pre-order it for 30% off by buying it directly from the publisher:
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Rewriting complex SQL for high performance
