DB2 Explain Facility with db2exfmt
By Tom Nonmacher
Welcome to another insightful post on SQLSupport.org. Today, we will delve into the world of DB2 and focus on one of its powerful tools - The DB2 Explain Facility with db2exfmt. This tool is a critical resource when it comes to understanding the efficiency of your SQL queries and identifying any potential issues that may be affecting your query performance.
In DB2, the Explain Facility provides detailed information about the access path that DB2 uses to execute SQL statements. It reveals how DB2 plans to execute an SQL query and what indexes it intends to use. This is where db2exfmt comes in. It is a utility that makes the output of the Explain Facility more readable and easier to understand.
-- To run the db2exfmt tool, use the following command:
-- db2exfmt -d mydb -e myschema -g TIC -w -1 -n % -s % -o db2exfmt.txt
-- This will generate a text file (db2exfmt.txt) that contains the formatted output.
When comparing this to other technologies, SQL Server 2019 has a similar tool, the Execution Plan feature. This can be accessed through SQL Server Management Studio (SSMS), and it provides a visual representation of the execution plan for your SQL queries, showing how the query optimizer plans to execute them.
-- To view the execution plan in SQL Server, use the following command:
-- SET SHOWPLAN_ALL ON;
-- Then run your query.
MySQL 8.0 also has an equivalent feature called the EXPLAIN statement. This statement provides information about how MySQL executes queries. It works with SELECT, DELETE, INSERT, REPLACE, and UPDATE statements.
-- To use the EXPLAIN statement in MySQL, use the following command:
-- EXPLAIN SELECT * FROM table_name;
-- This will display information about how MySQL plans to execute the query.
When it comes to cloud-based databases, Azure SQL Database and Azure Synapse Analytics also offer similar features. Azure SQL Database provides an Actual Execution Plan feature that shows the actual query execution plan with performance metrics. Azure Synapse Analytics provides a visual Explain feature that shows a graphical representation of the query execution plan.
In conclusion, understanding how your database system executes queries is crucial to optimizing performance and identifying potential issues. Whether you're using DB2, SQL Server, MySQL, or Azure SQL, these tools are invaluable for any database administrator or developer. Keep exploring these features and improving your SQL queries!