How to get MySQL status in a query

Question

Is it possible to use the server status variables in a MySQL query?

I can see various metrics from 'show status' but how do I calculate derived values (e.g. the query cache hit ratio)

show global status like 'Qcache_inserts';
show global status like 'Qcache_not_cached';
show global status like 'Qcache_hits';

Ho do I get Qcache_hits/(Qcache_hits+Qcache_inserts+Qcache_not_cached)?

Answer 1

generally you can access that info due this select:

SELECT
   VARIABLE_NAME,
   VARIABLE_VALUE
 FROM
   INFORMATION_SCHEMA.GLOBAL_STATUS

You could make the calculation you want like this:

select (g1.VARIABLE_VALUE / (g1.VARIABLE_VALUE + g2.VARIABLE_VALUE + g3.VARIABLE_VALUE)) as result
FROM INFORMATION_SCHEMA.GLOBAL_STATUS g1
inner join INFORMATION_SCHEMA.GLOBAL_STATUS g2
inner join INFORMATION_SCHEMA.GLOBAL_STATUS g3
where g1.VARIABLE_NAME = 'Qcache_hits'
and g2.VARIABLE_NAME = 'Qcache_inserts'
and g3.VARIABLE_NAME = 'Qcache_not_cached'