Question

我最近不得不解决这个问题，发现我过去多次需要这些信息所以我想我会发布它。假设下面的表def，您将如何编写查询以查找两者之间的所有差异？

表格def：

CREATE TABLE feed_tbl
(
code varchar(15),
name varchar(40),
status char(1),
update char(1)
CONSTRAINT feed_tbl_PK PRIMARY KEY (code)

CREATE TABLE data_tbl
(
code varchar(15),
name varchar(40),
status char(1),
update char(1)
CONSTRAINT data_tbl_PK PRIMARY KEY (code)

这是我的解决方案，作为使用联盟加入的三个查询的视图。指定的diff_type是记录需要更新的方式：从_data(2)删除，在_data(1)中更新，或添加到_data(0)

CREATE VIEW delta_vw AS (
SELECT     feed_tbl.code, feed_tbl.name, feed_tbl.status, feed_tbl.update, 0 as diff_type
FROM         feed_tbl LEFT OUTER JOIN
                      data_tbl ON feed_tbl.code = data_tbl.code
WHERE     (data_tbl.code IS NULL)

UNION

SELECT     feed_tbl.code, feed_tbl.name, feed_tbl.status, feed_tbl.update, 1 as diff_type
FROM         data_tbl  RIGHT OUTER JOIN
                      feed_tbl ON data_tbl.code = feed_tbl.code
where (feed_tbl.name <> data_tbl.name) OR
(data_tbl.status <> feed_tbl.status) OR
(data_tbl.update <> feed_tbl.update) 


UNION

SELECT     data_tbl.code, data_tbl.name, data_tbl.status, data_tbl.update, 2 as diff_type
FROM         feed_tbl LEFT OUTER JOIN
                      data_tbl ON data_tbl.code = feed_tbl.code
WHERE     (feed_tbl.code IS NULL)

)

Answer 1

UNION将删除重复项，因此只需将两者联合起来，然后搜索包含多个条目的任何内容。将“代码”作为主键，您可以说：

编辑0：修改为包含PK字段本身的差异

编辑1：如果您在现实生活中使用它，请务必列出实际的列名称。不要使用dot-star，因为UNION操作要求结果集具有完全匹配的列。如果您从其中一个表添加/删除列，则此示例将中断。

select dt.*
from
  data_tbl dt
 ,( 
  select code
  from
    (        
    select * from feed_tbl
    union
    select * from data_tbl        
    )
  group by code
  having count(*) > 1    
  ) diffs  --"diffs" will return all differences *except* those in the primary key itself 
where diffs.code = dt.code
union  --plus the ones that are only in feed, but not in data
select * from feed_tbl ft where not exists(select code from data_tbl dt where dt.code = ft.code)
union  --plus the ones that are only in data, but not in feed
select * from data_tbl dt where not exists(select code from feed_tbl ft where ft.code = dt.code)

Answer 2

我会在第二个union中使用一个小变体：

where (ISNULL(feed_tbl.name, 'NONAME') <> ISNULL(data_tbl.name, 'NONAME')) OR
(ISNULL(data_tbl.status, 'NOSTATUS') <> ISNULL(feed_tbl.status, 'NOSTATUS')) OR
(ISNULL(data_tbl.update, '12/31/2039') <> ISNULL(feed_tbl.update, '12/31/2039'))

由于我从未理解的原因，NULL不等于NULL（至少在SQL Server中）。

Answer 3

您还可以在FULL OUTER JOIN列上使用CASE ... END和diff_type语句以及querying 2 tables with the same spec for the differences中提到的where条款

这可能会在一个查询中实现相同的结果。

查询具有相同规格的2个表的差异

3 个答案: