The Basics of SQL Tuning
There is always a tendency to follow the tried and tested methods in order to get expected results and avoid surprising errors. But the method that we are all following might be of detriment to the greater good and there might exist some better way to perform that same task only. Therefore it is always a good idea to look for alternatives for a problem and determine the best way to solve it. The same thing can be done for coding and testing a systems problem and in database systems this is explicitly known as SQL Tuning. As can be gathered from its name, SQL Tuning deals with testing and finding the optimal solution in terms of the code to a given problem.
There are a certain number of tuning strategies that perks up the performance of a code when used, some of these tuning strategies are:-
- The traditional way to select all the elements from any group or class is to employ the tried and tested “Select *” function call which selects each and every one of them in a single call. But this method is not optimal in terms of time-coefficient and can be bettered by using “Select” and “From” statements and selecting individual elements one by one from the group. Although it might be hard work but results are much better.
- Another popular tuning strategy is to substitute the “Having” clause in a query and replace it with the “Where” statement instead. In the first case, the query selects all the elements at first and filters them on the basis of the condition while in the second case, the filtering is done first and then the required elements are selected resulting in better performance.
- The keyword “In” should be used predominantly when the task is of filtering the sub-queries of a main query as it can be quite slow in filtering the main query itself. Instead the “Exists” statement can be put to use in that case and it gives much better results when compared to not only “In” but also the popular “Distinct” keyword when joining tables.
- An optimal code should also consider the least number of sub-queries in any query as they take up a lot of time and energy to process by the system. Also, in place of the “Union” statement the “Union All” statement should be preferred as it selects all the elements at once when joining two groups. Moreover, any large binary object should be first kept in a file before processing.
- Lastly, the “Decode” operator should be used to avoid scanning the same row again and again and also the usage of the “Where” clause and the column variables should be minimized as much as possible.
These are some of the popular SQL Tuning methods commonly employed by coders when writing an SQL query. Not only do they satisfy all the coder’s needs in terms of functionalities but also enhances the performance of it manifold. Therefore, it is a good habit to practice SQL Tuning yourself.
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