DB2中的遞歸查詢以獲取鏈中的所有項目

Question

我必須通過僅提供一個作爲輸入來檢索通過貸款鏈接的所有客戶端。例如我有一個表的數據作爲

TABLEA

LOAN_ID CLIENT_ID 
1   7 
1   8 
2   7 
4   8 
4   9 
4   10 
5   9 
5   11 
13  2 
14  3 

如果我已經給僅輸入作爲CLIENT_ID = 7，則查詢有選擇除了最後兩個列中的所有從上面表中的列因爲CLIENT_ID 7具有1 ，2 LOAN_ID和1中的CLIENT_ID 8具有loan_id = 4，並且在該貸款中，CLIENT_id 9具有5個loan_id。

我們可以在DB2中爲存儲過程寫一個sql查詢嗎？

Answer 1

這裏的答案是使用遞歸CTE查詢你的問題：

WITH links AS 
(SELECT 
    loan_id, 
    client_id as c1, 
    client_id as c2, 0 as distance 
    FROM 
    myTable 
    -- recursion 
    UNION ALL 
    SELECT 
    t.loan_id, 
    l.c1 as c1, 
    tt.client_id as c2, 
    distance = distance + 1 
    FROM 
    links l INNER JOIN 
    myTable t ON l.c2 = t.client_id 
    AND l.loan_id != t.loan_id INNER JOIN 
    myTable tt ON t.loan_id = tt.loan_id 
    AND t.client_id != tt.client_id 
) 
SELECT * FROM myTable t 
WHERE EXISTS 
    (SELECT * FROM links 
    WHERE c2 = t.client_id and c1 = 7); 

http://sqlfiddle.com/#!3/8394d/16

我已經離開distance查詢裏面，使其更容易理解。