將列轉換爲Postgres中的行

Question

我的表名是osk,st,item。 osk字段是stid,stock,free,npr,itemno。 st字段是stid,name。項目字段是id,name。我有多個架構。每個模式都有這個表像這樣

Name St.Name Stock FreeStock 
    A  B   10  20 
    D  B   10  10 
    C  E   12  10 

select i.name,st.name,stock,freestock from osk,st,items i where i.id=osk.itemno 
and st.stid=osk.stid 

該查詢返回的結果，但我想

Name B (stock)  B(Free) E(Stock) E (Free Stock) 
    A  10   20   -   - 
    D  10   10   -   - 
    C  -   -   12   10 

如何達致這。 （我有多個模式，所有模式都有這張表，我想從所有模式中取回）

上午使用postgresql 9.3。如果可能使用CrossTab？如何使用它？

Answer 1

假設你有一個這樣的表（猜，因爲你沒有提供確切的表定義）：

create table some_table (
    name text, 
    stname text, 
    stock int, 
    freestock int 
); 

insert into some_table values 
('A', 'B', 10, 20), 
('D', 'B', 10, 10), 
('C', 'E', 12, 10); 

現在你可以使用crosstab功能這樣的記錄在這裏：http://www.postgresql.org/docs/current/static/tablefunc.html

create extension if not exists tablefunc; 

select coalesce(stock.name, freestock.name) as name, 
     stock.b as "B (stock)", 
     freestock.b as "B (free)", 
     stock.e as "E (stock)", 
     freestock.e as "E (free)" 
from 
    crosstab(' 
     select name, 
      stname, 
      stock 
     from some_table 
    ', ' 
     select distinct stname 
     from some_table 
     order by stname 
    ') as stock(name text, b int, e int) 
full outer join 
    crosstab(' 
     select name, 
      stname, 
      freestock 
     from some_table 
    ', ' 
     select distinct stname 
     from some_table 
     order by stname 
    ') as freestock(name text, b int, e int) 
on stock.name = freestock.name; 

導致：

name | B (stock) | B (free) | E (stock) | E (free) 
------+-----------+----------+-----------+---------- 
A |  10 |  20 |   | 
C |   |   |  12 |  10 
D |  10 |  10 |   | 
(3 rows)