Question

以下查询在teradata中有效，有没有办法在postgresql中编写相同的查询？运行此ppostgresql 10时出现错误

select *
from
    product
qualify
    row_number() over (partition by product_key order by product_no) = 1;

Answer 1

Postgres的distinct on应该更高效：

select distinct on (product_key) p.*
from product p
order by product_key, product_no;

这通常是Postgres中每组获取一行的最佳方法。

Answer 2

您需要子查询：

select p.*
from (select p.*,
             row_number() over (partition by product_key order by product_no) as seq
      from product p
     ) p 
where seq = 1;

有没有一种方法可以在PostgreSQL中使用qualify

2 个答案: