php - MYSQL存储过程2个表，2个select和1个update请求到同一张表

Question

我有一个函数:

// Search user who have zero city but not zero country
list($user_id, $country_id) = $site_db->query("
  select user_id, country_id
  from users 
  WHERE city_id < 1 AND country_id > 1
  LIMIT 1");

// If user found, get random city from user country
if ($user_id > 0) 
{
  $random_city_query = $site_db->query("
    select id 
    from cities 
    WHERE country_id = $country_id 
    order by RAND() 
    limit 1");

// Update user city
$update_city = $site_db->query("
  update users 
  set city_id = $random_city_query
  WHERE user_id = $user_id");
}

我尝试在这个函数的基础上创建MYSQL存储过程。

我已经尝试了一些变体，但它不会起作用:(

BEGIN
update users u 
set u.city_id = (select ci.id from cities ci WHERE ci.country_id = u.country_id order by RAND() limit 1)
WHERE user_id = (select u.user_id WHERE u.city_id < 1 AND u.country_id > 1 limit 1)
END

有人可以帮帮我吗？

Answer 1

所以，没人帮我 :( 我又花了 2 个小时自己创建程序 :)

BEGIN
SELECT @user_id := user_id from users WHERE city_id < 1 AND country_id > 1 LIMIT 1;
IF NOT @user_id IS NULL
THEN 
SELECT @user_country_id := country_id from users WHERE user_id = @user_id;
SELECT @city_id := id from cities WHERE country_id = @user_country_id order by RAND() limit 1;
update users set city_id = @city_id WHERE user_id = @user_id;
END IF;
END