是否可以将MySQL中的select exists查询中的值分配给存储过程中的多个变量？

Question

set sender_id =（选择EXISTS（SELECT 1 FROM account WHERE account_id = p_sender_id））;设置viewer_id =（选择EXISTS（选择1从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; 

了解更多关于SELECT...INTO。

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回复您的评论：

如果你想运行一个子查询同时设置：

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);