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我有以下表格（这些表格包含许多记录，但为了这个示例，我仅将内容缩减为我想要操作的记录）。

产品

 product_id | product_name 
------------+--------------
          1 | PRODUCT

合同

 contract_id | version | status | product_id 
-------------+---------+--------+------------
           2 |       1 | 30     |          1
           2 |       2 | 30     |          1
           2 |       3 | 30     |          1
           2 |       4 | 30     |          1
           2 |       5 | 30     |          1
           2 |       6 | 30     |          1

人们

 id | guid 
----+------
  3 |  123
  9 |  456

限制

 id | type 
----+------
  4 | 12
  5 | 14

链接表

 link_id | version | contract_id | object_type | function | obj_id 
---------+---------+-------------+-------------+----------+--------
       6 |       1 |           2 | XADL        | ADLTYP   |      4
       7 |       2 |           2 | XADL        | ADLTYP   |      5
       8 |       2 |           2 | BCBP        | BCA010   |    123
      10 |       3 |           2 | BCBP        | BCA010   |    456

这是上述表格的 DDL...

CREATE TABLE products (
  product_id    integer PRIMARY KEY,
  product_name  varchar(10) NOT NULL
);

CREATE TABLE contracts (
  contract_id   integer,
  version   integer,
  status    varchar(2) NOT NULL,
  product_id    integer NOT NULL REFERENCES products(product_id),
  PRIMARY KEY (contract_id, version)
);

CREATE TABLE link_table (
  link_id   integer,
  version   integer,
  contract_id   integer NOT NULL,
  object_type   varchar(4) NOT NULL,
  function  varchar(6) NOT NULL,
  obj_id    integer NOT NULL,
  PRIMARY KEY(link_id, version)
);

CREATE TABLE people (
  id    integer PRIMARY KEY,
  guid  integer,
  CONSTRAINT person_guid UNIQUE(guid)
);

CREATE TABLE limits (
  id    integer PRIMARY KEY,
  type  varchar(2) NOT NULL
);

现在...我的任务是为表中的字段选择最新版本的值以获取type表limits中值的最新id版本people。该表link_table决定了最新版本是什么。此数据需要提供字段contract_id, status, product_name。

我尝试了以下查询，不幸的是，当我应该只收到一个具有最新值的行时，我收到了两行。

SELECT c.contract_id, status, product_name, type
  FROM
    contracts AS c
  INNER JOIN
    products AS p
  ON c.product_id = p.product_id
  INNER JOIN
    link_table AS per
  ON c.contract_id = per.contract_id
  INNER JOIN
    link_table AS ll
  ON per.contract_id = ll.contract_id
  INNER JOIN
    people AS peop
  ON per.obj_id = peop.guid
  INNER JOIN
    limits AS lim
  ON ll.obj_id = lim.id
  WHERE 
    peop.id = 3
    AND per.object_type = 'BCBP'
    AND per.function = 'BCA010'
    AND ll.object_type = 'XADL'
    AND ll.function = 'ADLTYP'
    AND ll.version IN ( SELECT max(version) FROM link_table WHERE link_id = ll.link_id)
    AND per.version IN ( SELECT max(version) FROM link_table WHERE link_id = per.link_id)
    AND c.version IN ( SELECT max(version) FROM contracts WHERE contract_id = c.contract_id );

我期望的结果是

 contract_id | status | product_name | type 
-------------+--------+--------------+------
           2 | 30     | PRODUCT      | 12

然而实际结果是

 contract_id | status | product_name | type 
-------------+--------+--------------+------
           2 | 30     | PRODUCT      | 12
           2 | 30     | PRODUCT      | 14

我已经为此苦苦挣扎了一天多。谁能告诉我我做错了什么？这个例子是用 PostgreSQL 完成的，但真正的问题需要用 ABAP 的 OpenSQL 来解决，所以我不能使用UNION.

这是一些用于填充表的 SQL。

INSERT INTO products VALUES (1, 'PRODUCT');
INSERT INTO contracts VALUES (2, 1, '30', 1);
INSERT INTO contracts VALUES (2, 2, '30', 1);
INSERT INTO contracts VALUES (2, 3, '30', 1);
INSERT INTO contracts VALUES (2, 4, '30', 1);
INSERT INTO contracts VALUES (2, 5, '30', 1);
INSERT INTO contracts VALUES (2, 6, '30', 1);
INSERT INTO people VALUES (3, 123);
INSERT INTO people VALUES (9, 456);
INSERT INTO limits VALUES (4, '12');
INSERT INTO limits VALUES (5, '14');
INSERT INTO link_table VALUES (6, 1, 2, 'XADL', 'ADLTYP', 4);
INSERT INTO link_table VALUES (7, 2, 2, 'XADL', 'ADLTYP', 5);
INSERT INTO link_table VALUES (8, 2, 2, 'BCBP', 'BCA010', 123);
INSERT INTO link_table VALUES (10, 3, 2, 'BCBP', 'BCA010', 456);

编辑

看起来如果以下记录在table_link

 link_id | version | contract_id | object_type | function | obj_id 
---------+---------+-------------+-------------+----------+--------
       6 |       1 |           2 | XADL        | ADLTYP   |      4
       7 |       2 |           2 | XADL        | ADLTYP   |      5

用相同的定义，link_id那么我的查询将完全返回我想要的。

 link_id | version | contract_id | object_type | function | obj_id 
---------+---------+-------------+-------------+----------+--------
       7 |       1 |           2 | XADL        | ADLTYP   |      4
       7 |       2 |           2 | XADL        | ADLTYP   |      5

不幸link_id的是，每次生产中都会生成新的，即使version复合键中有一个...看起来我必须找到另一种方法或在链接表中寻找对我有帮助的其他字段。

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