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Author: Dan Tow SQL Server Query Performance Tuning Distilled Oracle Performance Troubleshooting With Dictionary Internals SQL & Tuning Scripts. SQL Tuning—. Generating Optimal. Execution Plans by Dan Tow; published by O 'Reilly, Summary. Overall review: Excellent. Target audience: Anyone. Sql tuning dan tow pdf free. Free Pdf Download For more dog articles, see the main Dogs page. Sql tuning dan tow pdf free. Direct Link #1.
But how to find out which column has the best coefficient?
In order to get the next index column we need to run same scripts including the first column. As a result of this query we can form the index [Type], [State], [expiration date].
But this method only works when we have known constants used in query execution. In other case, selectivity of the column can be quickly evaluated by the purpose of the column, i. For example, selectivity of the field Age will be higher than that of the field Sex. Apart from the purpose of the column, we can find out selectivity by using statistics on the column.
When not to use indexes Apart from knowing the importance of a column order inside the index, it is also important to know when indexes will not work, in other words, when even if some indexes are introduced, the whole table is scanned anyway. Indexes are not used when: Function or operation is applied to a column. But it is necessary to set a condition that would produce the smallest amount of results.
Optimal order of joining tables The order of joining tables requires similar approach to selectivity coefficient index.
It is best to join tables starting with the one that will produce the least amount of results after filtering. But there is a way to make it follow the predesigned order.
Hints for a query optimizer Although query optimizer is fairly independent when it comes to making decisions, there is still a way to control it. We can use query hints to introduce changes in the execution plan.
This operation can be useful when it is necessary to check the usefulness of adding a certain index. Statistics Query optimizer uses statistics to create execution plans. Statistics for SQL query optimization are objects with statistical information regarding the distribution of values inside an indexed view or columns of the table. If statistics is formed for an index or a table, then query optimizer can find the optimal execution plan faster.
You can form your own statistics or edit existing ones to help optimizer.
On the other hand, execution plans based on large and small volumes can be considerably different. Therefore, statistics will also be different. It is often necessary to check the work of your queries on a big database. But test data often not real cannot give the same precision that real data can. Also, it is not always possible to get the copy of a real-life database.
In this case, we can get statistics from the real database and load it to a test base. I have seen the book a couple of times Borders I think?
With the remarks Jonathan made it sounds like a reasonable investment. Wondering if Guy Harrison will get out a new or updated book at some point. I always thought his book was a great starting point for many developers new to oracle. I recall being very impressed with the book when I first read it cover to cover, and having just pulled it off the shelf to review, there is a great deal of helpful information in the book which may be of interest to the OP.
But, stay away from pages of that book. Larger block sizes can often improve scan performance. I think that Connor and Jonathan have pretty well demonstrated that this may be a lost cause.
I believe he's more into MySQL now. But meanwhile he did a great job by co building Quest Spotlight on Oracle. Although I only made it three quarters through due to pressure of work and a change of role. It presents a useful means of conceptualising what the optimizer does without requiring as much analytical maths as Jonathans book.
As it deals with concepts, it is not Oracle specific, but Oracle does get a few mentions. I read this after Cost Based Oracle : Fundamentals. I found I enjoyed CBOF more, though Dan Tows book gave me a different and useful way of thinking about the SQL optimization problem, as well as a graphical means of query representation.