Question

我生成了以下表格：

  here  | there |      cost
 -------+-------+--------------+
  {1,1} | {1,2} |          0.0 | 
  {1,1} | {2,1} |          0.0 | 
  {1,2} | {1,3} |          1.0 |      
  {2,1} | {2,2} |          1.0 |
  {2,1} | {3,1} |          1.0 |
  {1,2} | {2,2} |          1.0 |      
  {1,3} | {1,4} |          2.0 |       
  {2,2} | {2,3} |          2.0 |       
 ...
  {1,2} | {1,3} |          3.0 |

正如您所看到的，我有两个不同的费用{1,2}, {1,3} 我怎样才能保持每对的最佳价值？

Answer 1

此查询将以最低成本返回所有唯一对（此处，那里）：

SELECT
    here,
    there,
    MIN(cost)
FROM
    table_name
GROUP BY
    here,
    there;

Answer 2

如果您要保留整行（包含更多列），请使用DISTINCT ON：

SELECT DISTINCT ON (here, there) *
FROM   tbl
ORDER  BY here, there, cost;

找到最好的价值 - PostgreSQL

2 个答案: