CREATE TABLE head (
  cod INT,
  summ INT
)
ENGINE = INNODB;	

CREATE TABLE body (
  codHead INT,
  price INT
)
ENGINE = INNODB;	

INSERT INTO head (cod,summ) VALUES (1,0);

INSERT INTO body (codHead,price) VALUES (1,1);
INSERT INTO body (codHead,price) VALUES (2,2);


UPDATE head SET summ = (SELECT SUM(price) FROM body WHERE codHead=1);

UPDATE head INNER JOIN (SELECT codHead,SUM(price) as summ FROM body GROUP BY codHead) as A ON head.cod=A.codHead SET head.summ=A.summ;