mysql - 如果值不为空，则为 DATEDIFF

Question

这是此 question 的后续内容我之前发布过。

我正在使用以下语法计算 DATEDIFF 的 SUM

SUM(DATEDIFF(COALESCE(e.time_period_to, NOW()), e.time_period_from)) / COUNT(DISTINCT e.company_id)

我现在想要的是计算SUM的DATEDIFF仅当 e.time_period_from is NOT NULL

我尝试了以下查询。

SUM(IF(e.time_period_from IS NOT NULL), DATEDIFF(COALESCE(e.time_period_to, NOW()), e.time_period_from), 0) / COUNT(DISTINCT e.company_id)

这给了我 SQL 语法错误。

如何去做？

更新:

这是我完整的 MySQL 查询

SELECT
    SQL_CALC_FOUND_ROWS
    u.id,
    u.name,
    u.email,
    COUNT(DISTINCT(question_id)) as number_of_answered_questions,
    (SELECT option_id FROM answer WHERE user_id = u.id GROUP BY option_id ORDER BY COUNT(option_id) DESC LIMIT 1) as option_id,
    SUM(IF(e.time_period_from IS NOT NULL), DATEDIFF(COALESCE(e.time_period_to, NOW()), e.time_period_from), 0) / COUNT(DISTINCT e.company_id) AS tenure_in_days
FROM
    user u
LEFT JOIN
    role r ON (r.id = u.role_id)
LEFT JOIN
    answer a ON (a.user_id = u.id)
LEFT JOIN
    employment e ON (e.user_id = u.id)
WHERE
    r.slug = 'app_user'
GROUP BY
    u.id
LIMIT
    0, 10

如您所见，这是针对子选择的，我无法在其之外放置 where 条件。

这是我得到的错误。

"SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '), DATEDIFF(COALESCE(e.time_period_to, NOW()), e.time_period_from), 0) / COUNT(D' at line 1"

谢谢。

Answer 1

就像我之前的评论一样，我认为你只是把括号设置错误了，你想要得到的是这样的:

SUM(IF(e.time_period_from IS NOT NULL, DATEDIFF(COALESCE(e.time_period_to, NOW()), e.time_period_from), 0))
/ COUNT(DISTINCT e.company_id)