Postgres generate_series每个唯一行

Question

I'm trying to do something like this

key | series
____________
  1 |   1
  1 |   2
  2 |   1
  3 |   1
  3 |   2
  3 |   3
  4 |   1
  4 |   2

How do I go about generating a series for each unique key?

Answer 1

Use a window function ROW_NUMBER() :

SELECT key, 
       row_number() over (partition by key) series
FROM table1
;

Demo: http://www.sqlfiddle.com/#!15/a6301/4