我有一个带有非常大的表的mysql数据库。我经常运行涉及聚合函数的查询。使用MIN、MAX、SUM、COUNT等聚合函数的查询运行速度非常慢。请帮我提高速度。SELECT MIN(PeriodTime) FROM ResultsTable WHERE (OrderId=271)
SELECT COUNT(*) FROM ResultsTable WHERE
我正在使用MySQL。c1.pid IN ( -- where that pid is in the set: FROM Catalog AS c2 -- from catalog
WHERE c2.pid = c1.pid AND COUNT(c2.sid) >= 2 -- where there are at least two correspondi
$qs = 'SELECT cnam,COUNT(*) as cnt FROM cdr WHERE '.$where.'GROUP BY COUNT(*)';while($obj = mysql_fetch_array($objRs)) if ($obj它说这个问题就在这里:
while($obj =
datetime PK,此查询返回传感器4的最新日期,但返回传感器4的最老数据:from sensor_data这些查询返回数据的正确值:from sensor_dataand date = (selectmax(date) from sensor_data where sensor_id = 4)
order by date de
FieldValuefood fruitfood vegetableCOUNT(case when `FieldValue` = 'fruit' then 1 end)AS `counts`WHEREFieldValue` AS `type`,
COUNT(case when `FieldValue` = '