sqlServer2005递归的实现_with bomcte-优快云博客

本文介绍如何创建物品信息表（Items）与物料清单表（BOM），并使用CTE递归查询来计算物料清单中各层级物料的数量累积乘积。

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CREATE   TABLE   Items
(
      itemid       VARCHAR(5)     NOT   NULL   PRIMARY   KEY,
      itemname   VARCHAR(25)   NOT   NULL,
      /*   other   columns,   e.g.,   unit_price,   measurement_unit   */
)
CREATE   TABLE   BOM
(
      itemid           VARCHAR(5)   NOT   NULL   REFERENCES   Items,
      containsid   VARCHAR(5)   NOT   NULL   REFERENCES   Items,
      qty                 INT                 NOT   NULL
      /*   other   columns,   e.g.,   quantity   */
      PRIMARY   KEY(itemid,   containsid),

      CHECK   (itemid   <>   containsid)
)
SET   NOCOUNT   ON
INSERT   INTO   Items(itemid,   itemname)   VALUES('A',   'Item   A')
INSERT   INTO   Items(itemid,   itemname)   VALUES('B',   'Item   B')
INSERT   INTO   Items(itemid,   itemname)   VALUES('C',   'Item   C')
INSERT   INTO   Items(itemid,   itemname)   VALUES('D',   'Item   D')
INSERT   INTO   Items(itemid,   itemname)   VALUES('E',   'Item   E')
INSERT   INTO   Items(itemid,   itemname)   VALUES('F',   'Item   F')
INSERT   INTO   Items(itemid,   itemname)   VALUES('G',   'Item   G')
INSERT   INTO   Items(itemid,   itemname)   VALUES('H',   'Item   H')
INSERT   INTO   Items(itemid,   itemname)   VALUES('I',   'Item   I')
INSERT   INTO   Items(itemid,   itemname)   VALUES('J',   'Item   J')
INSERT   INTO   Items(itemid,   itemname)   VALUES('K',   'Item   K')
INSERT   INTO   BOM(itemid,   containsid,   qty)   VALUES('E',   'J',   1)
INSERT   INTO   BOM(itemid,   containsid,   qty)   VALUES('C',   'E',   3)
INSERT   INTO   BOM(itemid,   containsid,   qty)   VALUES('A',   'C',   2)
INSERT   INTO   BOM(itemid,   containsid,   qty)   VALUES('H',   'C',   4)
INSERT   INTO   BOM(itemid,   containsid,   qty)   VALUES('C',   'B',   2)
INSERT   INTO   BOM(itemid,   containsid,   qty)   VALUES('B',   'F',   1)
INSERT   INTO   BOM(itemid,   containsid,   qty)   VALUES('B',   'G',   3)
INSERT   INTO   BOM(itemid,   containsid,   qty)   VALUES('A',   'B',   2)
INSERT   INTO   BOM(itemid,   containsid,   qty)   VALUES('A',   'D',   2)
INSERT   INTO   BOM(itemid,   containsid,   qty)   VALUES('H',   'I',   1)

--以下   CTE   计算数量的累积乘积：

WITH   BOMCTE(itemid,   containsid,   qty,   cumulativeqty,level)
AS
(
      SELECT   *,   qty ,0
      FROM   BOM
      WHERE   itemid   =   'A'

      UNION   ALL
      SELECT   BOM.*,   BOM.qty   *   BOMCTE.cumulativeqty, BOMCTE.level+1
      FROM   BOM
          JOIN   BOMCTE
              ON   BOM.itemid   =   BOMCTE.containsid
)
SELECT   *   FROM   BOMCTE