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[英]Sum and average multiple columns from different SQL tables with PHP/PDO
[英]SQL Average Multiple Columns
您将如何计算多列和行的平均值?
到目前为止我的代码是:
SELECT b.id, r.id, b.name, r.business_id, (r.service + r.value + r.quality) / 3 AS average
FROM business b
LEFT JOIN rating r ON r.business_id = b.id
我想得到r.service,r.value和r.quality的平均值,并结合business_id列。
所以我应该得到:business_id = average:9.42(例如)
聚合函数AVG应该采用表达式进行聚合,因此这应该有效:
SELECT b.name, r.business_id, AVG((r.service + r.value + r.quality)/3)
FROM business b
LEFT JOIN rating r ON r.business_id = b.id
GROUP BY b.name, r.business_id
LIMIT 0,30
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