是否可以在 MySQL 查询中使用服务器状态变量?
我可以从“显示状态”中看到各种指标,但如何计算派生值(例如查询缓存命中率)
show global status like 'Qcache_inserts';
show global status like 'Qcache_not_cached';
show global status like 'Qcache_hits';
如何获得 Qcache_hits/(Qcache_hits+Qcache_inserts+Qcache_not_cached)?
通常,您可以通过以下选择访问该信息:
SELECT
VARIABLE_NAME,
VARIABLE_VALUE
FROM
INFORMATION_SCHEMA.GLOBAL_STATUS
您可以像这样进行您想要的计算:
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'
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