mysql - 使用另一个表列的平均数据更新列

Question

我写了一个像这样的命令，用另一个表中的平均列更新一个表中的列。它给出了错误

UPDATE college_rating,products set 
property1_avg =  avg(college_rating.rating1),
property2_avg =  avg(college_rating.rating2),
property3_avg =  avg(college_rating.rating3),
property4_avg =  avg(college_rating.rating4),
property5_avg =  avg(college_rating.rating5),
property6_avg =  avg(college_rating.rating6),
property7_avg =  avg(college_rating.rating7),
property8_avg =  avg(college_rating.rating8),
property9_avg =  avg(college_rating.rating9),
property10_avg =  avg(college_rating.rating10),
property11_avg =  avg(college_rating.rating11),
property12_avg =  avg(college_rating.rating12),
property13_avg =  avg(college_rating.rating13),
property14_avg =  avg(college_rating.rating14),
property15_avg =  avg(college_rating.rating15) 
where products.alias = concat(college_rating.property1,'-',college_rating.property2,'-',college_rating.property3) 
group by college_rating.property1,college_rating.property2, college_rating.property3

Answer 1

MySQL多表更新语法不允许使用group by。

您可以通过将聚合移动到子查询中并在多表更新中加入该子查询来完成您想要做的事情。

这样的事情应该有效:

update products p
inner join (
  select concat(property1,'-',property2,'-',property3) as alias,
  avg(rating1) as property1_avg,
  avg(rating2) as property2_avg,
  avg(rating3) as property3_avg,
  avg(rating4) as property4_avg,
  avg(rating5) as property5_avg,
  avg(rating6) as property6_avg,
  avg(rating7) as property7_avg,
  avg(rating8) as property8_avg,
  avg(rating9) as property9_avg,
  avg(rating10) as property10_avg,
  avg(rating11) as property11_avg,
  avg(rating12) as property12_avg,
  avg(rating13) as property13_avg,
  avg(rating14) as property14_avg,
  avg(rating15) as property15_avg 
  from college_rating
  group by property1,property2, property3
) as r on r.alias = p.alias
set p.property1_avg = r.property1_avg,
p.property2_avg = r.property2_avg,
p.property3_avg = r.property3_avg,
p.property4_avg = r.property4_avg,
p.property5_avg = r.property5_avg,
p.property6_avg = r.property6_avg,
p.property7_avg = r.property7_avg,
p.property8_avg = r.property8_avg,
p.property9_avg = r.property9_avg,
p.property10_avg = r.property10_avg,
p.property11_avg = r.property11_avg,
p.property12_avg = r.property12_avg,
p.property13_avg = r.property13_avg,
p.property14_avg = r.property14_avg,
p.property15_avg = r.property15_avg;