根据两个数据库表之间的数据比较创建oracle视图

Question

我有以下表格：

• 我想创建视图，以便对于两个表中的descr = 'O' 和常见的id_isin 字段值，检查ratio 字段并只取ratio 字段值较低的行。
• 对于descr = 'O'，如果 id_isin 存在于一个表中但不存在于另一个表中，则取这些行（双向）
• 对于descr ! = 'O' 所在的所有行，从表IS_ID_TST 中获取所有这些行。

以下是视图的预期输出，例如：

ID_ISIN   QUOTE_CRNY   DESCR           RATIO              ALLOCATIONASSETTYPE
L000123    USD              O              0.0769          Other total
L000129    USD              O              0.0669          Other total
D123458    USD              O              0.64039         Other total
M123456    USD              O              5.64039         Other total
F563458    USD              C              0.84039         Other total
G123456    USD              null           0.04039         Other total
L000123    USD              C              5.0769          Other total

我可以根据这个条件创建视图吗？

Answer 1

您需要 LEAST() 函数以及 3 个子查询以及 UNION 子句。其中两个子查询应在表中包含FULL JOIN：

CREATE VIEW V_MEMBER_FUND AS    
SELECT i.fund_isin,
       i.member_descr,
       LEAST(i.member_ratio, t.member_ratio) AS member_ratio,
       i.allocationassettype
  FROM IS_ID i
  JOIN IS_ID_TST t
    ON t.fund_isin = i.fund_isin
   AND t.member_descr = i.member_descr
 WHERE i.member_descr = 'O'
UNION
SELECT LEAST(NVL(i.fund_isin,t.fund_isin),NVL(t.fund_isin,i.fund_isin)) AS fund_isin,
       LEAST(NVL(i.member_descr,t.member_descr),NVL(t.member_descr,i.member_descr)) AS member_descr,
       LEAST(NVL(i.member_ratio,t.member_ratio),NVL(t.member_ratio,i.member_ratio)) AS member_ratio,
       LEAST(NVL(i.allocationassettype,t.allocationassettype),NVL(t.allocationassettype,i.allocationassettype)) AS allocationassettype
  FROM IS_ID i
  FULL JOIN IS_ID_TST t
    ON t.fund_isin = i.fund_isin
 WHERE (i.member_descr = 'O' OR t.member_descr = 'O' )
   AND ( t.fund_isin IS NULL OR i.fund_isin IS NULL )
UNION
SELECT t.fund_isin,
       t.member_descr,
       t.member_ratio,
       t.allocationassettype
  FROM IS_ID i
 RIGHT JOIN IS_ID_TST t
    ON t.fund_isin = i.fund_isin
   AND t.member_descr = i.member_descr
 WHERE (NVL(i.member_descr,'XYZ') != 'O' OR NVL(t.member_descr,'XYZ') != 'O' )
   AND t.fund_isin IS NOT NULL  

对于第一种情况：只需要返回与i.member_descr = 'O'匹配的member_ratio的最小值。

对于第二种情况：告知需要双向(FULL JOIN) 逻辑

对于第三种情况：需要一个与IS_ID_TST 表（在当前情况下为RIGHT JOIN）的位置相对应的外部联接以及非member_desct 与 'O' 的等效值（即使是 NULL 值也应该被消除，并为此目的添加 NVL() 函数）

并且在这三种情况下指定的所有子查询都应与UNION 组合，以提供逐行组合，包括消除重复行。

Demo

Answer 2

我提出了以下查询，请检查我已将 cmets 放在查询中。询问是否不符合您的要求或进行任何澄清。

CREATE VIEW v_combined_data AS
WITH combined_data
AS
(
SELECT t1.fund_isin
      ,t1.fund_quote_crny
      ,t1.member_descr
      ,t1.member_ratio
      ,t1.allocationassettype
      ,t2.fund_isin fund_isin_tst
      ,t2.fund_quote_crny fund_quote_crny_tst
      ,t2.member_descr member_descr_tst
      ,t2.member_ratio member_ratio_tst
      ,t2.allocationassettype allocationassettype_tst
FROM   is_id t1
FULL   OUTER JOIN is_id_tst t2
ON     t1.fund_isin = t2.fund_isin
AND    t1.fund_quote_crny = t2.fund_quote_crny
AND    t1.member_descr = t2.member_descr
)
-- for member_descr = 'O' and for common fund_isin field value from both tables, 
-- check the member_ratio field and take only the row where member_ratio field value is low.
SELECT d.fund_isin
      ,d.fund_quote_crny
      ,d.member_descr
      ,LEAST(d.member_ratio,d.member_ratio_tst) member_ratio
      ,d.allocationassettype
  FROM combined_data d
WHERE d.member_descr = 'O'
  AND d.fund_isin IS NOT NULL 
  AND d.fund_isin_tst IS NOT NULL
UNION ALL
--for member_descr = 'O' and if the fund_isin exist in one table but not in another then take those rows(bidirectional)
--exists in IS_ID and not in IS_ID_TST
SELECT d.fund_isin
      ,d.fund_quote_crny
      ,d.member_descr
      ,d.member_ratio
      ,d.allocationassettype
  FROM combined_data d
WHERE d.member_descr = 'O'
  AND NOT EXISTS (SELECT 1
                    FROM combined_data ci
                   WHERE ci.fund_isin_tst = d.fund_isin
                     AND ci.fund_quote_crny_tst = d.fund_quote_crny
                     AND ci.member_descr_tst = 'O')
UNION ALL
--for member_descr = 'O' and if the fund_isin exist in one table but not in another then take those rows(bidirectional)
--exists in IS_ID_TST and not in IS_ID
SELECT d.fund_isin_tst
      ,d.fund_quote_crny_tst
      ,d.member_descr_tst
      ,d.member_ratio_tst
      ,d.allocationassettype_tst
  FROM combined_data d
WHERE d.member_descr_tst = 'O'
  AND NOT EXISTS (SELECT 1
                    FROM combined_data ci
                   WHERE ci.fund_isin = d.fund_isin_tst
                     AND ci.fund_quote_crny = d.fund_quote_crny_tst
                     AND ci.member_descr = 'O')
UNION ALL
--for all the rows where member_descr ! = 'O', take all those rows from table IS_ID_TST
SELECT d.fund_isin_tst
      ,d.fund_quote_crny_tst
      ,d.member_descr_tst
      ,d.member_ratio_tst
      ,d.allocationassettype_tst
  FROM combined_data d
WHERE d.fund_isin_tst IS NOT NULL
  AND (d.member_descr_tst != 'O' OR d.member_descr_tst IS NULL);