從同一表中獲取單列記錄

Question

從數據表中檢索記錄時，我遇到了一些問題。 有人可以給我任何建議嗎？

Id LearnerId ConnectionId  IsApproved   
3   1            38       1
5   39           1        1 
7   1            31       1 
13  1            30       1 
31  1            40       1 
34  41           1        1 
35  31           1        1 
39  1            42       1 

這就是我的桌子的樣子。 我想在此表上使用選擇查詢來選擇記錄，如下所示：

AllId
38
39
31
30
40
41
31
42

我如何編寫查詢才能找到上述記錄列表？ 我想收集除1以外的所有ID。

Answer 1

您可以在兩個查詢之間使用UNION ALL 。 第一個將返回connectionid值，第二個將返回learnerid值：

select ConnectionId as AllId
from LearnerConnections
where LearnerId = 1
union all
select LearnerId as AllId
from LearnerConnections
where ConnectionId = 1

參見帶有演示的SQL Fiddle

Answer 2

SELECT CASE LearnerId
            WHEN 1 THEN ConnectionId
            ELSE LearnerId
       END AS AllId
FROM tablename

Answer 3

select  Id
from    YourTable
union all
select  LearnerId
from    YourTable
union all
select  ConnectionId
from    YourTable

Answer 4

SELECT  Id AS AllId
FROM    YourTable
union all
SELECT  LearnerId AS AllId
FROM        YourTable
union all
SELECT  ConnectionId AS AllId
FROM        YourTable

Answer 5

SELECT LearnerId AS AllId FROM tableName
WHERE ConnectionId = 1
UNION
SELECT ConnectionId AS AllId FROM tableName
WHERE LearnerId = 1