mysql - 是否可以将 MySQL 中 select exist 查询的值分配给存储过程中的多个变量？

Question

set sender_id = (Select EXISTS(SELECT 1 FROM account WHERE account_id = p_sender_id));

set viewer_id = (Select EXISTS(SELECT 1 FROM account WHERE account_id = p_viewer_id));

Answer 1

你可以这样做:

SELECT EXISTS(SELECT 1 FROM account WHERE account_id = p_sender_id)),
       EXISTS(SELECT 1 FROM account WHERE account_id = p_viewer_id))
INTO sender_id, viewer_id;

阅读更多关于 SELECT...INTO 的信息.

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回复你的评论:

如果你想运行一个子查询来设置两者:

SELECT
  MAX(CASE account_id WHEN p_sender_id THEN 1 ELSE 0 END),
  MAX(CASE account_id WHEN p_viewer_id THEN 1 ELSE 0 END)
INTO sender_id, viewer_id 
FROM account
WHERE account_id IN (p_sender_id, p_viewer_id);