SQL - 全外連接

Question

我在SQL數據庫三個表

我需要加入這個三個表讓臺這樣

我想聯接三個表來獲得整個第一，第三和第二（其中排序爲2）的所有數據表

我試試這個查詢

select table1.Item, table1.Location, table1.Type, 
     table2.Item, table2.Location, table2.Type,table2.Sort 
     table3.Item, table3.Location, table3.Type 
    from table1 
full outer join table2 
    on table1.Item = table2.Item 
    and table1.Location = table2.Location 
    and table1.Type = table2.Type 
    and table2.Sort = '2' 
full outer join table3 
    on table1.Item = table3.Item 
    and table1.Location = table3.Location 
    and table1.Type = table3.Type 

但我只得到這個表

如何使查詢來獲取表我想與所有的組合？

有什麼想法？

Answer 1

select table1.Item, table1.Location, table1.Type, 
     table2.Item, table2.Location, table2.Type, table2.Sort, 
     table3.Item, table3.Location, table3.Type 
from table1 
    full outer join table3 
    on table1.Item = table3.Item 
    and table1.Location = table3.Location 
    and table1.Type = table3.Type 
    full outer join table2 
    on (table1.Item = table2.Item 
    and table1.Location = table2.Location 
    and table1.Type = table2.Type 
    and table2.Sort = '2' 
    ) 
    or (table3.Item = table2.Item 
    and table3.Location = table2.Location 
    and table3.Type = table2.Type 
    and table2.Sort = '2' 
    ) 
where (table2.Sort = '2' or table2.Sort is null) 

rextester演示：http://rextester.com/MNW25175

結果

+------+----------+-------+------+----------+-------+------+------+----------+-------+ 
| Item | Location | Type | Item | Location | Type | Sort | Item | Location | Type | 
+------+----------+-------+------+----------+-------+------+------+----------+-------+ 
| 123 | A  | small | NULL | NULL  | NULL | NULL | 123 | A  | small | 
| NULL | NULL  | NULL | 123 | A  | big | 2 | 123 | A  | big | 
| NULL | NULL  | NULL | 123 | B  | small | 2 | NULL | NULL  | NULL | 
+------+----------+-------+------+----------+-------+------+------+----------+-------+ 

---

這也適用，但只是因爲table2有一個匹配的table1所有行，這可能不適合你的實際使用情況：

select table1.Item, table1.Location, table1.Type, 
     table2.Item, table2.Location, table2.Type, table2.Sort, 
     table3.Item, table3.Location, table3.Type 
from table1 
    full outer join table3 
    on table1.Item = table3.Item 
    and table1.Location = table3.Location 
    and table1.Type = table3.Type 
    full outer join table2 
    on table3.Item = table2.Item 
    and table3.Location = table2.Location 
    and table3.Type = table2.Type 
    and table2.Sort = '2' 
where (table2.Sort = '2' or table2.Sort is null) 

Answer 2

使用LEFT OUTER JOIN：

SELECT * FROM Table 2 
LEFT OUTER JOIN Table 1 ON table1.Item = table2.Item AND table1.Location = 
        table2.Location AND table1.Type = table2.Type and 
        table2.Sort = '2' 
LEFT OUTER JOIN Table 3 ON table1.Item = table3.Item 
       and table1.Location = table3.Location 
       and table1.Type = table3.Type 

Answer 3

你的做法是正確的，你就錯過是你的第二個加入審覈規定使用​​3210。

第一outer join將返回一組行的一些null值在裏面，如果你使用的第三join規定 - 這些價值觀，病情會不會滿意。

可以解決使用​​3210這個問題，將使用第二個參數，如果第一個是null

select table1.Item, table1.Location, table1.Type, 
     table2.Item, table2.Location, table2.Type,table2.Sort 
     table3.Item, table3.Location, table3.Type 
from table1 
full outer join table2 
on  table1.Item = table2.Item and 
     table1.Location = table2.Location and 
     table1.Type = table2.Type 
full outer join table3 
on  coalesce(table1.Item, table2.Item) = table3.Item and 
     coalesce(table1.Location, table2.Location) = table3.Location and 
     coalesce(table1.Type, table2.Type) = table3.Type 
where coalesce(table2.Sort, 2) = 2 

Answer 4

你得到通過以下查詢

SELECT d.item, d.location, d.[type], 
    s.item, s.location, s.[type], s.sort, 
    h.item, h.location, h.[type] 
FROM tblData d 
    FULL OUTER JOIN tblSearchData s 
     ON d.item = s.item 
     AND d.location = s.location 
     AND d.[type] = s.[type] 
    FULL OUTER JOIN tblHelpData h 
     ON (s.item = h.item OR d.item=h.item) 
     AND (s.location = h.location OR d.location=h.location) 
     AND (s.[type] = h.[type] OR d.[type]=h.[type]) 
WHERE s.sort=2 OR s.sort IS NULL 

所需的結果