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問(wèn)題描述
我有一個(gè)包含 RequestId 和 OldRequestId 兩列的表格.
I have the table with the two columns RequestId and OldRequestId.
如果我傳遞一個(gè)
RequestId，它應(yīng)該檢索我的特定記錄.
If I pass a
RequestId, it should retrieve me the specific record.
如果檢索到的記錄中 OldRequestId 不為空，它也應(yīng)該帶上舊的請(qǐng)求數(shù)據(jù).
If the OldRequestId is not null in the retrieved record, it should bring the old request data as well.
它應(yīng)該一直持續(xù)到 OldRequestId 為空.
It should go on until the OldRequestId is null.
有人可以幫我為這個(gè)需求寫出最好的 SQL 查詢嗎?
Can someone help me to write the best possible SQL query for this requirement?
推薦答案
您可以使用遞歸公用表表達(dá)式 (CTE) 解決此問(wèn)題:
You can solve this using a recursive Common Table Expression (CTE):
DECLARE
@RequestID int = 6;
WITH
ReqCTE AS
(
SELECT
RequestID,
OldRequestID
FROM
Requests
WHERE
RequestID = @RequestID
UNION ALL SELECT
R.RequestID,
R.OldRequestID
FROM
ReqCTE C
INNER JOIN Requests R
ON R.RequestID = C.OldRequestID
)
SELECT
*
FROM
ReqCTE;
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