How to properly debug and inspect SQL Queries in PHP File?

Question

My website AdminPanel has a PHP file which takes almost 30-40 seconds in loading. I doubt the queries which are making the mess, but may be it is the code but the code structure seems perfect. I want to find and check the all the queries execution and running time i.e how much time it takes to execute? But i can't.

I tried the slow query logs option but it is not logging anything. And from the general log i just see queries but no execution time and details.

Thanks

• Rick James: More on slow log usage: mysql.rjweb.org/doc.php/mysql_analysis -- a common mistake is not setting log_output.

Answer 1

SET GLOBAL long_query_time = 1; to log slow queries taking 1 second or more.

EXPLAIN EXTENDED SELECT ..... to see valuable information about how the query is getting to the result.

Follow immediately in the same session, SHOW WARNINGS; to see how the Optimizer rearranged the sequence of events.
(Rick James, thanks for the reminder.)

• Rick James: (And SHOW WARNINGS; so you can see the "extended" stuff.)