MySQL，更新一个表连接多个表

Question

I'm trying to update one table from another that isn´t directly connected, through another table and the statement executes correctly, but it doesn't work because it's updating without data.

The query is:

UPDATE cities
INNER JOIN footprints ON cities.ID=footprints.ID 
INNER JOIN (SELECT code,id_code,sum(price) AS price FROM buildings GROUP BY code,id_code) AS SUM_Price ON footprints.code=SUM_Price.code AND footprints.id_code=SUM_Price.id_code
SET cities.Total_Price=SUM_Price.price

Add some sample data as example.

Example of Data tables

Does anyone know what is happening?

Thanks for your support!

Answer 1

First you must join footprints to buildings and aggregate and then join to cities :

UPDATE cities c
INNER JOIN (
  SELECT f.id, sum(b.price) price
  FROM footprints f INNER JOIN buildings b 
  ON f.code = b.code AND f.id_code = b.id_code
  GROUP BY f.id
) s ON s.id = c.id
SET c.total_price = s.price