选择并更新mysql相同的查询php

Question

您好我正在尝试在一个查询中组合UPDATE和SELECT语句。

这是我试过的那个。但没有工作。

$this->$db2->query('
  UPDATE users
  SET total = (total - (
    SELECT floatingnumber
    FROM posts
    WHERE post_id = "'.$this->post_id.'"
    LIMIT 1
  ))
  WHERE id = "'.$this->post_user->id.'"
  LIMIT 1
');

Answer 1

使用INNER JOIN尝试此项，而不使用SELECT

UPDATE users u 
INNER JOIN posts p
ON  // realationship between tables
 SET total = total - p.floatingnumber

WHERE p.post_id = "'.$this->post_id.'"

AND  u.id = "'.$this->post_user->id.'"

 LIMIT 1