MySQL COUNT加统计条件

COUNT((('字段名' = '条件') OR NULL)) 

-- 列子如下 在IP段列表显示下面IP总数量，空闲数量，故障数量
SELECT A.*,COUNT(B.id) AS totalip,COUNT(((B.use_status = 1) OR NULL)) AS idleip,COUNT(((B.use_status = 4) OR NULL)) AS faultip 
FROM icab_ipsegment AS A
LEFT JOIN icab_ip AS B ON A.id = B.ipsegment_id
GROUP BY A.id

执行结果

 

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