Database Optimization Techniques #3: Joins

    Database Optimization Techniques
    Posted February 6, 2019

    Increasing online presence has led to an emerging demand for reliable databases. With a lot of dependence on the database for the operations of the system, high performance of the database is always kept in high priorities. Any slowdowns in the database can affect the entire system’s performance.

    To avoid any disruptions in the operations to prevent any kind of loss for the enterprise, database performance tuning is practiced regularly under the supervision of diligent Database Administrators (DBAs). It is a regular practice of database optimization techniques, which enhances the performance of the database and resolve any possible issue even before it occurs.

    We have already discussed the database optimization techniques of Indexing and Identifying & Optimizing Slow Queries in the prequels of this article. Before we discuss the Database Optimization technique of Joins in this article, and how replacing Outer Joins with Inner Joins could enhance the database performance, let us first understand what database Joins are, how Inner and Outer Joins are different from one another and why are they important.

    What are Database Joins?

    Joins are operations in the SQL, which are used to establish connections between two or more tables in a database based on the logical relationships of the columns content of the two tables. The values of the two tables’ fields are familiar to one another.

    It is mainly used to retrieve data when two or more tables are required for the desired data. Since these tables are logically related to one another, join operation access these and retrieves the required data.

    To know more about the basics of Database Joins in MySQL read Joins Basics Tutorial.

    What are Inner and Outer Joins?

    Although, both the Inner and Outer Joins are used to retrieve the combined data from two or more database tables, yet both operate in a different manner. It is the join condition which specifies how the columns of the tables are to be matched with one another. Generally, it is the Foreign Key of one table which is matched with the Primary Key of the other.

    While in both the cases of Inner and Outer Joins, the rows from the tables which match are included, for Inner Join the non-matching values are excluded, while they are included for the Outer Join.

    In simple terms using the analogy of Set Theory Inner Join is analogical to the Intersection, while Outer Join is analogical to Union of the sets.

    How are Joins important for Database Optimization?

    While Joins are unavoidable in complex queries, where they are often used to retrieve data from using multiple tables. It is also a reason for the slow processing of the queries causing a slow data retrieval and a slower performance.

    Outer Joins, where the data which is to be processed for a query, is much more as compared to Inner Joins, especially when the database is huge, can cause significant delays. It is therefore advisable to prefer using Inner Joins over Outer Joins for optimizing database.

    Let’s understand this with an example, say table A and B has 1000 rows each. If the number of rows, which match in the tables is 100, and the remaining 900 do not match for both the tables. In case of Inner Join, only 100 rows which are matching have to be processed, while for Outer Join, 100 rows which match and 900 each of the two tables which do not match are to be processed.

    For the tables A and B, an Inner Join has to process 100 rows while Outer Join has to process 1900 rows, which takes more time than the former. That’s why it is always advised to use Inner Joins wherever possible instead of Outer Joins.

    The Next Step

    It is a diligent DBA with expertise, could find better alternatives for Joins and use them efficiently for database optimization, so as to execute the queries in the best turnaround time. Proactiveness, constant monitoring and diligent analysis are the key aspects which could be helpful in enhancing the database performance at scale.

    If you are looking for such qualities in a DBA consultant for your enterprise who could boost your database performance, then OptimizDBA could help you with our team of proactive database experts.

    At OptimizDBA, we are dedicated to making your database optimized by using our industry experience, latest technology and proactive problem solving approach. Feel free to contact us and we will be obliged to assist you with your database optimization and management to suit your business requirements at its best.


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