php - 如何避免在查询中包含子句？

Question

我正在处理这个成功运行的查询

select 
hash,
SUM(DATE(TIMESTAMP) = CURDATE()) as today,
sum(DATE(TIMESTAMP) between DATE_SUB(CURDATE( ), INTERVAL 7 DAY) and  DATE_SUB(CURDATE( ), INTERVAL 1 DAY)) as last_week

from behaviour

group by hash
having last_week > 0 and today > last_week
order by today desc

我正在努力优化它。

我正在尝试避免 last_week>0 进入 having 子句，但运气不佳。我收到“无效使用群组功能”

select 
hash,
SUM(DATE(TIMESTAMP) = CURDATE()) as today,
sum(DATE(TIMESTAMP) between DATE_SUB(CURDATE( ), INTERVAL 7 DAY) and  DATE_SUB(CURDATE( ), INTERVAL 1 DAY)) as last_week

from behaviour
where 
and (sum(DATE(TIMESTAMP) between DATE_SUB(CURDATE( ), INTERVAL 4 DAY) and  DATE_SUB(CURDATE( ), INTERVAL 1 DAY)) > 0)

group by hash
having today > last_week
order by today desc

如何优化它？因为在大表中执行大约需要 1 分钟。

Answer 1

您想在进行聚合之前进行过滤:

select hash,
       sum(DATE(TIMESTAMP) = CURDATE()) as today,
       sum(DATE(TIMESTAMP) between DATE_SUB(CURDATE( ), INTERVAL 7 DAY) and DATE_SUB(CURDATE( ), INTERVAL 1 DAY)) as last_week
from behaviour
where timestamp >= curdate() - interval 7 day
      timestamp < curdate() + interval 1 day
group by hash
having today > last_week and last_week > 0
order by today desc;

这减少了group by 所需的数据量——这应该会显着提高性能。您可以使用 (timestamp, hash) 上的索引进一步提高性能。

您仍然需要 having 子句，因为您需要对结果进行额外的过滤。不过，性能提升来自聚合之前的过滤。