使用平均分数更新MYSQL

Question

我有两个表流体和cas，我​​试图用cad表的平均分数更新相关的表液。像这样：

UPDATE fluids INNER JOIN cas on cas.cas = fluids.cas 
SET fluids.score = avg(cas.score) GROUP BY cas.cas

Answer 1

您需要将聚合选择包装为子查询：

UPDATE fluids 
INNER JOIN (
    SELECT cas,avg(cas.score) as avg_score
    FROM cas
    GROUP BY cas 
) as c ON c.cas = fluids.cas 
SET fluids.score = c.avg_score