SQL 中条件count()用sum()代替

摘要: count ()对于null不计数 现在要计数不为空的列
换一个sum方法 满足条件计1，不满足为0
后者效果耗时更低，性能是前者两倍以上

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SELECT

COUNT(

CASE WHEN ${x} > 0 THEN name ELSE NULL end) AS

addCount,

COUNT(

CASE WHEN ${y} > 0 THEN name ELSE NULL end) AS

delCount

FROM

tablename

where...

测试耗时：30min

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SELECT

SUM(

CASE WHEN ${x} > 0 THEN 1 ELSE 0end) AS addCount,

[b]SUM[/b](

CASE WHEN ${y} > 0 THEN 1 ELSE 0 end) AS delCount

FROM
tablename
where...

测试耗时8min

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