MySQL计算具有多行数据的2个日期之间的时间

Question

我有一个包含 2 列 date_picked_begin 和 date_picked 的表格，并且会有多行，每行都包含一个日期。

如何使用 TIMESTAMPDIFF 获取所有数据行中日期之间的秒数差异。

我尝试了以下查询，但它只返回与第一行的秒数差异。 (这是别名total_picking_waiting_time，它试图获取总时间)。

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

此外，我一直假设此查询获取所有行中两个日期之间的平均时间。是这样吗？由于它没有像我预期的那样返回总时间，我现在认为它不是。

谢谢

Answer 1

首先，FROM中的子查询是不必要的。它增加了查询的冗长性，实际上减慢了查询速度(因为 MySQL 实现了此类子查询)。

然后，要获取总拣选时间，请使用 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;