Postgres的：獲取鮮明的條目

Question

的補目前，我可以從這樣一個表中獲取不同的條目：

SELECT DISTINCT ON (abc.entry) abc.* FROM table abc 
    JOIN table1 def ON abc.entry = def.entry 
WHERE def.created >= 'some_date' AND def.position = 1; 

有沒有一種方式來獲得具有重複每個條目的條目（的即補？不同的組過some_date

Answer 1

您可以使用having條款來獲取在重複條目列表：

SELECT abc.entry 
FROM table abc JOIN 
    table1 def 
    ON abc.entry = def.entry 
WHERE def.created >= 'some_date' AND def.position = 1 
group by abc.entry 
having count(*) > 1 

要獲得行的名單，我將使用窗口功能：

select t.* 
from (SELECT abc.*, count(*) over (partition by entry) as cnt 
     FROM table abc JOIN 
      table1 def 
      ON abc.entry = def.entry 
     WHERE def.created >= 'some_date' AND def.position = 1 
    ) t 
where cnt > 1; 

編輯：

我看到過的術語的混亂。 DISTINCT在SQL中有非常特殊的含義。而且，DISTINCT ON在Postgres中有一個相當不同的含義。我認爲你必須用子查詢來做到這一點：

select abc.* 
from table abc left outer join 
    (SELECT DISTINCT ON (abc.entry) abc.* FROM table abc 
     JOIN table1 def ON abc.entry = def.entry 
     WHERE def.created >= 'some_date' AND def.position = 1 
    ) f 
    on abc.id = f.id 
where f.id is NULL 

雖然是一個謹慎的詞。您正在使用distinct on而沒有order by子句。數據中返回的特定行是不確定的。您應該在這裏添加order by到您的原始數據和子查詢。

select abc.* 
from table abc left outer join 
    (SELECT abc.entry, max(abc.id) as maxid 
     FROM table abc 
     JOIN table1 def ON abc.entry = def.entry 
     WHERE def.created >= 'some_date' AND def.position = 1 
     group by abc.entry 
    ) f 
    on abc.id = f.maxid 
where f.maxid is NULL