移調查詢PostgreSQL中

Question

我有如下表：

tb_item 
id_item | item_name | price 
---------------------------- 
1  | item1  | 2000 
2  | item2  | 3000 
3  | item3  | 4000 

和

tb_value 
id_value | id_item | value_type | value 
---------------------------------------- 
1  | 1  | bedroom | 2 
2  | 1  | bathroom | 1 
3  | 2  | bedroom | 3 
4  | 2  | bathroom | 1 
5  | 3  | bedroom | 4 
6  | 3  | bathroom | 2 

我想獲得類似這樣的輸出：

item_name | price | bedroom | bathroom 
--------------------------------------- 
item1  | 2000 | 2  | 1 
item2  | 3000 | 3  | 1 
item3  | 4000 | 4  | 2 

我使用PostgreSQL的;什麼查詢可以用來獲得這個輸出？ 我也使用PHP;有沒有一個PHP函數可以做到這一點？

Answer 1

您也可以與一對夫婦完成這個LEFT JOIN聲明

SELECT i.item_name 
    , i.price 
    , bed.value AS bedroom 
    , bath.value AS bathroom 
FROM tb_item AS i 
LEFT JOIN tb_value AS bed ON i.id_item = bed.id_item 
    AND bed.value_type = 'bedroom' 
LEFT JOIN tb_value AS bath ON i.id_item = bath.id_item 
    AND bath.value_type = 'bathroom' 

Answer 2

select item_name, price, bedroom.value as bedroom, bathroom.value as bathroom 
from tb_item, tb_value as bedroom, tb_value as bathroom 
where bedroom.id_item=tb_item.id_item and bedroom.value_type='bedroom' 
and bathroom.id_item=tb_item.id_item and bathroom.value_type='bathroom'