如果查詢返回null，count = 0 mysql

我正在運行下面的查詢。

SELECT cluster, 
     infra_properties.property_name property, 
     count(*) 
FROM raw_alerts, 
     infra_properties 
WHERE infra_properties.parent_group = raw_alerts.cluster 
     AND cluster = 'abuse-content' 
     AND infra_properties.property_name = 'BigBro' 
     AND timestamp BETWEEN '2012-12-24 00:00:00' AND '2012-12-24 23:59:59' 
GROUP BY cluster;

我得到的輸出爲空，但我的要求是得到計數= 0。如下所述。

+---------------+----------+----------+ 
| cluster  | property | count(*) | 
+---------------+----------+----------+ 
| abuse-content | BigBro | 0  | 
+---------------+----------+----------+ 
1 row in set (0.30 sec)

來源

2013-02-22 carlton moh

我跑了波紋管查詢，但仍然沒有運氣。選擇羣集，infra_properties.property_name屬性，COALESCE（COUNT（*），0）作爲從raw_alerts計數，infra_properties其中infra_properties.parent_group = raw_alerts.cluster和cluster ='abuse-content'和infra_properties.property_name ='BigBro'和時間戳之間'2013-1-24 00:00:00'和'2013-1-24 23:59:59'按羣組分組; – 2013-02-22 11:17:16

你嘗試過'count（cluster）'嗎？ – tttthomasssss 2013-02-22 11:22:39

是的，已經試過了 – 2013-02-22 11:29:25

如果2個表上沒有匹配的記錄，則不會返回任何行。

什麼你可能需要做的是有集羣和財產列額外的表，然後做一些事情，如： -

SELECT a.cluster, a.property, count(c.id) 
    FROM SomeExtraTable a 
    LEFT OUTER JOIN raw_alerts b ON a.cluster = b.cluster AND AND b.cluster = 'abuse-content' 
    LEFT OUTER JOIN infra_properties c 
ON a.property = c.property 
AND c.parent_group = b.cluster 
AND c.property_name = 'BigBro' 
AND c.timestamp BETWEEN '2012-12-24 00:00:00' AND '2012-12-24 23:59:59' 
    GROUP BY a.cluster, a.property

（我只是在猜測時間戳列是什麼表）

來源

2013-02-22 11:46:21 Kickstart

如果查詢返回null，count = 0 mysql

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