Sql Programming Tutorials, Guides & Best Practices

The output provides details like:

• Select Type: Type of query (simple, primary, subquery, etc.).
• Table: The table accessed by the query.
• Type: Type of access (e.g., index, ALL, ref, const).
• Possible Keys: Indexes considered by the optimizer.
• Key: Index used for the query.
• Rows: Estimated number of rows examined.
• Extra: Additional information, such as whether a temporary table or file sort is used.

SELECT columns
FROM table1
INNER JOIN table2
ON table1.common_column = table2.common_column;

Consider two tables, employees and departments: