Postgresql - 在列中有重複值的行中增加計數器

Question

我已將一列（seq）添加到用於調度的表中，因此前端可以管理每個項目可以顯示的順序。是否可以創建一個SQL查詢，以基於日期列中常見重複值的增量計數器填充此列？

之前

------------------------------------ 
| name | date_time   | seq | 
------------------------------------ 
| ABC1 | 15-01-2017 11:00:00 |  | 
| ABC2 | 16-01-2017 11:30:00 |  | 
| ABC1 | 16-01-2017 11:30:00 |  | 
| ABC3 | 17-01-2017 10:00:00 |  | 
| ABC3 | 18-01-2017 12:30:00 |  | 
| ABC4 | 18-01-2017 12:30:00 |  | 
| ABC1 | 18-01-2017 12:30:00 |  | 
------------------------------------ 

後

------------------------------------ 
| name | date_time   | seq | 
------------------------------------ 
| ABC1 | 15-01-2017 11:00:00 | 0 | 
| ABC2 | 16-01-2017 11:30:00 | 0 | 
| ABC1 | 16-01-2017 11:30:00 | 1 | 
| ABC3 | 17-01-2017 10:00:00 | 0 | 
| ABC3 | 18-01-2017 12:30:00 | 0 | 
| ABC4 | 18-01-2017 12:30:00 | 1 | 
| ABC1 | 18-01-2017 12:30:00 | 2 | 
------------------------------------ 

解決了，感謝兩個答案。 爲了使它更容易爲任何人誰發現這一點，工作代碼爲：

UPDATE my_table f 
    SET seq = seq2 
    FROM (
     SELECT ctid, ROW_NUMBER() OVER (PARTITION BY date_time ORDER BY ctid) -1 AS seq2 
     FROM my_table 
     ) s 
    WHERE f.ctid = s.ctid; 

Answer 1

使用window functionrow_number()：

with my_table (name, date_time) as (
values 

('ABC1', '15-01-2017 11:00:00'), 
('ABC2', '16-01-2017 11:30:00'), 
('ABC1', '16-01-2017 11:30:00'), 
('ABC3', '17-01-2017 10:00:00'), 
('ABC3', '18-01-2017 12:30:00'), 
('ABC4', '18-01-2017 12:30:00'), 
('ABC1', '18-01-2017 12:30:00') 
) 

select *, 
    row_number() over (partition by name order by date_time)- 1 as seq 
from my_table 
order by date_time; 

name |  date_time  | seq 
------+---------------------+----- 
ABC1 | 15-01-2017 11:00:00 | 0 
ABC1 | 16-01-2017 11:30:00 | 1 
ABC2 | 16-01-2017 11:30:00 | 0 
ABC3 | 17-01-2017 10:00:00 | 0 
ABC1 | 18-01-2017 12:30:00 | 2 
ABC3 | 18-01-2017 12:30:00 | 1 
ABC4 | 18-01-2017 12:30:00 | 0 
(7 rows) 

對類似的問題有關更新現有記錄有唯一的整數讀this answer。

Answer 2

退房ROW_NUMBER()。

SELECT name, date_time, ROW_NUMBER() OVER (PARTITION BY date_time ORDER BY name) FROM [table]