z/OS 数据库中的递归查询

Question

亲爱的，我有一个来源 table 名为“PROGRAM”，如下所示

Program CSECT
X       Y
B       X
M       P
A       L
B       D
C       D
A       C
B       C
A       B
D       B

给定一个程序，例如 'A' 我需要找到所有相关的 CSECT

Program CSECT
A       L
A       C
A       B
B       D
B       X
X       Y

我试过如下递归查询，但它循环了一个循环引用示例 B-D 和 D-B

WITH RPL (Program, Csect) AS
      (SELECT ROOT.Program, ROOT.Csect
         FROM Program ROOT
         WHERE Program = 'A'
      UNION ALL
         SELECT CHILD.Program, CHILD.Csect
            FROM RPL PARENT, Program CHILD
            WHERE PARENT.Csect = CHILD.Program)
 SELECT *
     FROM RPL;

Answer 1

您可以添加其他列（链），其中包含当前行的完整路径，如下所示。如果 CHILD.Program 已包含在此类路径中，则不应添加新行。

WITH RPL (Program, Csect, Chain) AS
(
SELECT ROOT.Program, ROOT.Csect, CAST('|' || ROOT.Program || '|' AS VARCHAR(1000))
FROM Program ROOT
WHERE Program = 'A'
    UNION ALL
SELECT CHILD.Program, CHILD.Csect, PARENT.Chain || CHILD.Program || '|' 
FROM RPL PARENT, Program CHILD
WHERE PARENT.Csect = CHILD.Program
    AND LOCATE('|' || CHILD.Program || '|', PARENT.Chain) = 0
)
SELECT DISTINCT Program, Csect
FROM RPL
ORDER BY Program;

z/OS 数据库中的递归查询

Recursive query in DB for z/OS

db2

zos