If you are a regular user of web, cloud, and communication services, you must have faced database challenges. The best way to address this problem is to use MySQL, which is a robust database management system that offers data protection and high efficiency.
While there are different types of MySQL queries with diverse functions, some queries don’t deliver the desired results. In this situation, database administrators can use MySQL query optimizer to execute a query and explore the MySQL explain plan. The EXPLAIN is a powerful tool in MySQL used at the beginning of any query statement to diagnose errors in the query statements and optimize the MySQL queries. Similarly, you can use the MySQL analyze query to monitor their query performance and effectively run the database applications.
In this article, we’ll discuss how can developers and database administrators use the MySQL explain visualizer to improve MySQL query performance.
Table of Contents
What is EXPLAIN?
As the name suggests, the term EXPLAIN refers to fetching detailed information regarding any process, function, or system. In MySQL, the EXPLAIN is a powerful profiling tool to monitor the manner in which the MySQL database executes the query statements.
With EXPLAIN, database administrators can check their execution plan, monitor the query performance, and make sure the query is using the correct indexes. Besides, they can get details about the statement execution plan by using Explain with these explainable statements:
- DELETE
- UPDATE
- SELECT
- INSERT
- REPLACE
- TABLE (MySQL 8.0.19 or later versions only)
Similarly, EXPLAIN is also used to plan, instrument, and execute the queries. Once a query has been executed, EXPLAIN displays the plan and measurements such as the time spent at various points and the number of rows, etc. This way, EXPLAIN offers data-driven insights and relevant explanations to help database managers optimize their MySQL queries for improved performance. A correct interpretation of an EXPLAIN statement can help you make your MySQL queries faster and deliver better results.
How to Use EXPLAIN?
If you want to let your audience understand a complicated concept, the best way to do this is to use simple, easy-to-understand, and concise language. So in this section, we’ll try to understand how to analyze MySQL query with the EXPLAIN by showing an example of MySQL code EXPLAIN statement.
As explained earlier, MySQL EXPLAIN describes the manner a query is executed by the SQL database. For example, look at this simple MySQL EXPLAIN query:
By using the EXPLAIN command before the SELECT statement, MySQL displays the order in which processes take place in the statement execution plan.
Now, let’s consider a bit more complicated MySQL query:
The output, once the EXPLAIN command is executed, is given below:
It is clearly visible from the above two examples that the EXPLAIN simplifies the information in MySQL query making it easy to understand for database managers. This way, you can maximize the performance with MySQL query precision and optimize the relevant indices as indicated in the extra EXPLAIN column.
Now, let’s take another example of a company’s database. Here, we have two different tables with information regarding customers and orders placed. Given below are the SQL statements database managers will execute to create the database for this information:
The following statement displays a table containing information about orders:
The following statement displays a table containing information about customers:
Now, we shall use the EXPLAIN command before the SELECT statement that gives us simplified information about customers as shown in the figure below:
We get a single table query as output without special clauses like UNION or JOIN. Since there were only three records in the customers’ table, the output value of EXPLAIN contains three rows only.
Now, let’s apply the EXPLAIN statement in the SELECT query of both customers and orders table. This time, we will also use a WHERE condition and the JOIN clause. The output of this EXPLAIN statement is given below:
To understand this output of the EXPLAIN statement, please refer to the following table that describes the terms used in the column.
| Term | Description |
| id | Query identifier |
| select_type | Type of the SELECT query |
| table | Name of the table |
| partitions | Table partitions |
| type | Type of JOIN |
| possible_keys | Key used by MySQL to find rows |
| key | The index used by the MySQL |
| key_len | Index length used by the MySQL query optimizer |
| ref | Columns compared to the index |
| rows | List of records under examination |
| filtered | Estimated percentage of table rows to be filtered |
| extra | Additional info about query execution plan. |
When to Use EXPLAIN?
So far, we have discussed the power of MySQL EXPLAIN query with examples. However, the question of when to use EXPLAIN still remains unanswered. Here, we shall cover this topic.
Given below are some scenarios where you must use the EXPLAIN command:
- To confirm if your MySQL query performs well
- To diagnose errors in the query statements
- View the statement execution plan
- Obtain additional information about the execution plan
- Examine queries with partitioned tables
- Ensure the MySQL query optimizer joins the tables in the proper order
- Fetch information such as the number of rows, execution cost, time spent executing this iterator, number of loops, etc.
- Display information in the table columns
For example, you can use the dbForge Studio for MySQL to debug code or develop stored routines. For this purpose, start debugging the query with EXPLAIN clouse and obtain information about the SELECT statement execution plan from the EXPLAIN statement. Next, compile the stored procedure, function, or trigger with debug information by using the dbForge Studio debugger tool. The full-fledged MySQL GUI of dbForge Studio for MySQL will help you debug code or analyze data tables with ease.
Conclusion
The EXPLAIN is a powerful profiling tool in the MySQL database that allows users to obtain useful information about execution plans, table structure, number of rows, time consumed, etc. By using the EXPLAIN command before explainable statements, you regularly monitor your query execution plan and ensure the query is using the correct indexes.
Hence, database administrators and developers can use the EXPLAIN command to improve their MySQL Query performance and gain actionable insights from MySQL explain visualizer to make data-driven decisions.