MySQL SELECT 查询选择中的 where 子句

Question

SELECT *, j.company_id as companyid, j.id as jid, p.id as pid, f.id as fave_id, f.user_id as user_id
FROM people p
LEFT JOIN job j 
ON p.job_id = j.id
LEFT JOIN favourites f
ON p.id = f.people_id
WHERE p.company_id = 1
ORDER BY p.id ASC

我有上面的 MySQL 查询，它工作得很好，但最后两部分是我需要整理的。

默认情况下，在每一行中，它们输出 null，否则它们输出整数，例如 fave_id 作为 46 和 user_id如 6

我实际上需要弄清楚的是，如果 fave_id 和 user_id 在我的头脑中都不为空，是否可以从查询的 SELECT 部分输出像这样的东西

SELECT *, j.company_id as companyid, j.id as jid, p.id as pid, f.id as fave_id, f.user_id as user_id, [if fave_id && user_id then favorite = true] 
FROM people p
LEFT JOIN job j 
ON p.job_id = j.id
LEFT JOIN favourites f
ON p.id = f.people_id
WHERE p.company_id = 1
ORDER BY p.id ASC

Answer 1

一个CASE语句将用于检查值并返回所需的值:

SELECT *, j.company_id as companyid, j.id as jid, p.id as pid, f.id as fave_id, f.user_id as user_id, 
    (CASE WHEN fave_id IS NOT NULL AND user_id IS NOT NULL THEN 1 ELSE 0 END) AS favorite 
FROM people p
LEFT JOIN job j 
ON p.job_id = j.id
LEFT JOIN favourites f
ON p.id = f.people_id
WHERE p.company_id = 1
ORDER BY p.id ASC