DATEDIFF如果值不为NULL

我使用的语法如下计算DATEDIFF的SUM

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

我现在要的是计算DATEDIFFSUM只有e.time_period_from is NOT NULL

我尝试下面的查询。

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。

如何去呢？

UPDATE：

这里是我的全部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

正如你看到这是一个子选择我不能把where条件之外吧。

这里是我得到的错误。

"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。

来源

2016-01-08 Ibrahim Azhar Armar

什么是错误 –

我想你刚刚得到括号ng，IF有3个参数，第一个是条件，第二个是条件为真的值，第三个是假的值。但条件后您的括号关闭 –

@VipinJain让我更新。 –

在我的评论之前，我想你刚才设置括号错了，你要得到的是这样的：

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)

来源

2016-01-08 09:09:58

谢谢凯指出，它工作:) –

我检查查询错误在这行

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

用这个代替以上线代码

SUM(IF(e.time_period_from IS NOT NULL, DATEDIFF(COALESCE(e.time_period_to, NOW()), e.time_period_from), 0));

来源

2016-01-08 09:15:55

DATEDIFF如果值不为NULL

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