SQL 查询，摆脱重复选择

Question

我在 python 中使用 sqlite3，我有一个包含以下列的表：

recordid(int)、username(text)、locations(text)、types(text)、occupancy(int)、time_added(datetime)、token(text) 和 (undo)。

我有以下查询，我根据占用情况从表中选择数据，添加的时间在用户输入的两个指定时间之间，即 start_date 和 end_date：

('''SELECT locations, types, 
           (SELECT COUNT (occupancy) FROM traffic WHERE undo = 0 AND occupancy = 1 AND types = ? AND time_added BETWEEN ? AND ?),
           (SELECT COUNT (occupancy) FROM traffic WHERE undo = 0 AND occupancy = 2 AND types = ? AND time_added BETWEEN ? AND ?),
           (SELECT COUNT (occupancy) FROM traffic WHERE undo = 0 AND occupancy = 3 AND types = ? AND time_added BETWEEN ? AND ?),
           (SELECT COUNT (occupancy) FROM traffic WHERE undo = 0 AND occupancy = 4 AND types = ? AND time_added BETWEEN ? AND ?),
    FROM traffic WHERE types = ? GROUP BY type''', 
(vehicle, start_date, end_date, vehicle, start_date, end_date, vehicle, start_date, end_date, vehicle, start_date, end_date, vehicle)

有没有办法压缩这个，所以我不必为了改变占用而多次复制和粘贴相同的东西？我尝试使用 for 循环，但这并没有真正让我有所收获。

干杯！

Answer 1

我很确定可以大大简化查询：

SELECT type
       SUM( occupancy = 1 ) as cnt_1,
       SUM( occupancy = 2 ) as cnt_2,
       SUM( occupancy = 3 ) as cnt_3,
       SUM( occupancy = 4 ) as cnt_4
FROM traffic
WHERE undo = 0 AND
      type = ? AND
      time_added BETWEEN ? AND ?
GROUP BY type;

不过，我不确定这是否正是您的问题所在。