如何轉置 postgresql 中的表值？

Question

如何轉置這些值以獲取此表：

讓它看起來像這樣：

There's no Pivot function that I can use in postgresql and every time I try the crosstab function, I keep getting an error in my code. 假設我的表名為 select * 來自 TAttributes

Answer 1

使用條件聚合，在 Postgres 中意味着filter ：

select id,
       max(attributenumber) filter (where attributeid = 2000),
       max(attributenumber) filter (where attributeid = 2001),
       max(attributenumber) filter (where attributeid = 2002),
       max(attributenumber) filter (where attributeid = 2003)
from t
group by id;

這是一個 db<>fiddle。

Answer 2

嘗試這個：

SELECT id,  
    MAX((SELECT attributenumber FROM public.t WHERE ext_t.id = id AND ext_t.attribuiteid = attribuiteid AND attribuiteid = 2000)) AS '2000',
    MAX((SELECT attributenumber FROM public.t WHERE ext_t.id = id AND ext_t.attribuiteid = attribuiteid AND attribuiteid = 2001)) AS '2001',
    MAX((SELECT attributenumber FROM public.t WHERE ext_t.id = id AND ext_t.attribuiteid = attribuiteid AND attribuiteid = 2002)) AS '2002',
    MAX((SELECT attributenumber FROM public.t WHERE ext_t.id = id AND ext_t.attribuiteid = attribuiteid AND attribuiteid = 2003)) AS '2003' 
FROM public.t ext_t GROUP BY id