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素材网站哪个好,找人做网站流程,怎么做能让网站尽快收录,广州海珠网站建设case when 在sql 中非常方便数据不同维度统计，但是也会出现mysql 索引不命中问题，当多个case 出现时，需要提取出来到where里面优化优化后 SELECT date(RecordTime) AS date, count( DISTINCT CASE WHEN Param 1 …

case when 在sql 中非常方便数据不同维度统计，但是也会出现mysql 索引不命中问题，当多个case 出现时，需要提取出来到where里面优化

优化后

SELECT
   date(RecordTime) AS date,
   count(
       DISTINCT CASE
       WHEN `Param` = '1' THEN
           UserID
       END
   ) AS 'h',
   count(
       DISTINCT CASE
       WHEN `Param` = '2' THEN
           UserID
       END
   ) AS 's',
   count(
       DISTINCT CASE
       WHEN `Param` = '4' THEN
           UserID
       END
   ) AS 'z'
FROM
   user_prop_log_202310
WHERE
   Category = '42'
GROUP BY
   DATE(RecordTime)

优化前：

SELECT
   date(RecordTime) AS date,
   count(
       DISTINCT CASE
       WHEN `Category` = '42'
       AND `Param` = '1' THEN
           UserID
       END
   ) AS 'h',
   count(
       DISTINCT CASE
       WHEN `Category` = '42'
       AND `Param` = '2' THEN
           UserID
       END
   ) AS 's',
   count(
       DISTINCT CASE
       WHEN `Category` = '42'
       AND `Param` = '4' THEN
           UserID
       END
   ) AS 'z'
FROM
   user_prop_log_202310
GROUP BY
   DATE(RecordTime)