Information directs all troubleshooting. It is very important to know what is happening in the server process. I have discussed ways to get this information throughout this book, but here I will add some missing details about the tools discussed.
INFORMATION_SCHEMA is a schema that provides information about database
SHOW queries are now
SELECT statements from
INFORMATION_SCHEMA tables. You can
INFORMATION_SCHEMA tables like
any other table; this is their great advantage over other tools. The only
problem is that
tables are not optimized to work fast, so queries on them can be slow,
especially on tables that contain information about many objects.
I won’t describe each and every table here, because the MySQL
Reference Manual contains a great deal of detail about their structure
Instead, I’ll show a few queries to demonstrate the sort of useful
information you can get from the
INFORMATION_SCHEMA. You’ll still need the user
manual for details. I put the link to the 5.6 MySQL Reference Manual
here because I mention a few tables introduced in this version.
To get an idea of what can be done with
INFORMATION_SCHEMA, let’s start by extracting
an overview of how many tables in each storage engine are in current
use. I’m excluding the
from the list because all its tables always use the MyISAM storage