postgresql - 在匹配上加入表，但也不匹配？

Question

所以我有一個加入，它的工作原理，但它並沒有顯示我想要的所有數據。目前我想查看device_interface.c1中的每一行，如果device_interface.c1 = device_inventory.c1那麼我想在列中看到。現在我只看到device_interface.c1 = device_inventory.c1。

下面是我的查詢：

SELECT 
    device_info.pk, 
    device_interface.fk, 
    device_interface.c1, 
    device_interface.c2, 
    device_inventory.c1 
FROM 
    "test".device_info, 
    "test".device_interface, 
    "test".device_inventory 
WHERE 
    device_info.pk = device_interface.fk AND 
    device_info.pk = device_inventory.fk AND 
    device_interface.c1 = device_inventory.c1 AND 
    device_interface.c2 = 'Physical' 

示例輸出：期望的輸出的

device_info.pk device_interface.c1 device_inventory.c1 
1      1      1 
1      3      3 
1      95     95 
2      55     55 
2      634     634 

實施例：

device_info.pk device_interface.c1 device_inventory.c1 
1      1      1 
1      2   
1      3      3 
1      4 
1      5 
1      6 
1      95     95 
2      55     55 
2      56 
2      57 
2      634     634 

Answer 1

甲left join應該做的伎倆：

SELECT 
    device_info.pk, 
    device_interface.fk, 
    device_interface.c1, 
    device_interface.c2, 
    device_inventory.c1 
FROM 
    "test".device_info 
LEFT JOIN 
    "test".device_interface 
ON 
    device_info.pk = device_interface.fk 
LEFT JOIN 
    "test".device_inventory 
ON 
    device_info.pk = device_inventory.fk AND 
    device_interface.c1 = device_inventory.c1 
WHERE 
    device_interface.c2 = 'Physical'