SQL联合在where子句中带有Coalesce（？）

Question

我正在尝试将旧的帮助台记录合并到更新的帮助台应用程序中。 我仍然拥有旧帮助台应用程序中的所有数据，它使用与新应用程序相同的字段，但位于不同的文件中。 对于较新的应用程序来说，此select语句工作得很好，它可以搜索所有过去的调用以查找特定的内容，无论它是关键字还是分配给谁等等。

SELECT status, identity, description, contact, scan_text, extended_desc, allocated_to
 FROM   helpdesk.table1
 WHERE  UPPER(allocated_to) = coalesce(?, allocated_to) 
  AND   identity = coalesce(?, identity) 
  AND   description = coalesce(?, description) 
  AND   contact= coalesce(?, contact) 
  AND UPPER(scan_text) LIKE coalesce(?,scantext)
  and upper(extended_desc) like coalesce(?, extended_desc)
 ORDER by allocated, identity desc

我想做的是使用某种联合，所以我只能用一个框来搜索新记录和旧记录，而不是两个不同的框，并且必须记住数据的存储位置。 我以为这样的事情可能会起作用，但是我认为我的where子句太含糊了，我几乎尝试了在字段前面包括一个库的所有组合。

Select *
From
(
select status, identity, description, contact, scan_text, extended_desc, allocated_to
 from helpdesk.table1
Union                                   
select status, identity, description, contact, scan_text, extended_desc, allocated_to
 from helpdesk.table2
)
WHERE   UPPER(allocated_to) = coalesce(?, allocated_to) 
  AND   identity = coalesce(?, identity) 
  AND   description = coalesce(?, description) 
  AND   contact= coalesce(?, contact) 
  AND UPPER(scan_text) LIKE coalesce(?,scantext)
  and upper(extended_desc) like coalesce(?, extended_desc)
 ORDER by allocated, identity desc

如果仅对两个选择进行联合，那么我将从两个表中获取所有记录，但是我需要能够将结果范围缩小到关键字或某种其他类型的字段，例如在第一段代码中。 如果有人能指出正确的方向，我将不胜感激。

我可能还应该说这是db2，而sql正在Web应用程序上运行。 因此，当此sql运行时，它会生成下拉框或文本字段，以将您自己的文字放入其中以缩小所有帮助台调用的结果。

Answer 1

如果我理解正确，则需要指示记录来自哪个表的指示器。 如果是这样的话：

Select *
From (select 'old' as which, status, identity, description, contact, scan_text, extended_desc, allocated_to
      from helpdesk.table1
      Union all                                
      select 'new', status, identity, description, contact, scan_text, extended_desc, allocated_to
      from helpdesk.table2
     ) hd
WHERE UPPER(allocated_to) = coalesce(?, allocated_to) AND
      identity = coalesce(?, identity) AND
      description = coalesce(?, description) AND
      contact= coalesce(?, contact) AND
     UPPER(scan_text) LIKE coalesce(?,scantext) AND
     upper(extended_desc) like coalesce(?, extended_desc)
ORDER by allocated, identity desc;

然后，您可以添加相应的where逻辑上which列（并重新命名为任何你想和列）。

Answer 2

您总是可以只在要合并的两个select语句中放置where。 可能比合并两个表然后进行筛选要快。

SELECT * FROM  helpdesk.table1
WHERE   UPPER(allocated_to) = coalesce(?, allocated_to) 
  AND   identity = coalesce(?, identity) 
  AND   description = coalesce(?, description) 
  AND   contact= coalesce(?, contact) 
  AND UPPER(scan_text) LIKE coalesce(?,scantext)
  and upper(extended_desc) like coalesce(?, extended_desc)
UNION ALL 
SELECT * FROM  helpdesk.table2
WHERE   UPPER(allocated_to) = coalesce(?, allocated_to) 
  AND   identity = coalesce(?, identity) 
  AND   description = coalesce(?, description) 
  AND   contact= coalesce(?, contact) 
  AND UPPER(scan_text) LIKE coalesce(?,scantext)
  and upper(extended_desc) like coalesce(?, extended_desc)
ORDER BY allocated, identity desc;

只需在第二次选择后下订单即可。 如果您担心大小写，则UPPER(allocated_to) = coalesce(?, UPPER(allocated_to))语法可能会更好。

Answer 3

我不知道这是否特定于我正在使用的Web应用程序生成器，或者是否可以在其他SQL中将其用于其他地方，但是您可以引用参数，并通过称为parameter parameter的参数将它们传递给幕后。联合的后半部分中的1、2、3。 通过仅在第一个位置输入您输入的内容，这解决了具有两组用户输入框的问题。 这是对我有用的代码的最终版本

SELECT status, identity, description, contact, scan_text, extended_desc, allocated_to
FROM   helpdesk.table1
WHERE  UPPER(allocated_to) = coalesce(?, allocated_to) 
 AND   identity = coalesce(?, identity) 
 AND   description = coalesce(?, description) 
 AND   contact= coalesce(?, contact) 
 AND UPPER(scan_text) LIKE coalesce(?,scantext)
 and upper(extended_desc) like coalesce(?, extended_desc)

Union

SELECT status, identity, description, contact, scan_text, extended_desc, allocated_to
FROM   helpdesk.table2
WHERE  UPPER(allocated_to) = coalesce(??1, allocated_to) 
 AND   identity = coalesce(??2, identity) 
 AND   description = coalesce(??3, description) 
 AND   contact= coalesce(??4, contact) 
 AND UPPER(scan_text) LIKE coalesce(??5,scantext)
 and upper(extended_desc) like coalesce(??6, extended_desc)
ORDER by allocated, identity desc

谢谢那些试图帮助我的人。