MySQL在兩個日期之間的計數時間與多行數據

Question

我有一個表，其中包含2列date_picked_begin和date_picked並將有多個行中包含每個日期。

如何使用TIMESTAMPDIFF獲取所有數據行中日期之間的差值。

我已經嘗試了以下查詢，但它僅返回第一行中的差異秒數。 （這是別名total_picking_waiting_time這是試圖獲得總時間）。

SELECT COUNT(pi.pi_id) AS num_picking_waiting_time, 
AVG(TIMESTAMPDIFF(SECOND, pi.date_picked_begin, pi.date_picked)) AS average_picking_waiting_time, 
TIMESTAMPDIFF(SECOND, pi.date_picked_begin, pi.date_picked) AS total_picking_waiting_time 
FROM (SELECT pi_id, type, date_picked_begin, date_picked, picker FROM pickwave_items) as pi 
WHERE pi.type = 'Picking (Waiting Time)' AND DATE(pi.date_picked) = '2017-02-25' AND pi.picker = 1 

而且，我一直在假設該查詢是越來越所有行中的兩個日期之間的平均時間。是這樣嗎？由於它沒有像我預期的那樣返回總時間，我現在認爲它不是。

謝謝

Answer 1

首先，在FROM子查詢是不必要的。它增加了查詢的冗長度，並且實際上減慢了它的速度（因爲MySQL實現了這樣的子查詢）。

然後，爲了得到總採摘時間，使用SUM()：

SELECT COUNT(pi.pi_id) AS num_picking_waiting_time, 
     AVG(TIMESTAMPDIFF(SECOND, pi.date_picked_begin, pi.date_picked)) AS average_picking_waiting_time, 
     SUM(TIMESTAMPDIFF(SECOND, pi.date_picked_begin, pi.date_picked)) AS total_picking_waiting_time 
FROM pickwave_items as pi 
WHERE pi.type = 'Picking (Waiting Time)' AND 
     DATE(pi.date_picked) = '2017-02-25' AND 
     pi.picker = 1;