将JOINed行添加到已过滤的SELECT结果中

Question

我有一个返回某些特定数据的查询：

  SELECT sub.*
  FROM (
Select item_id, field_id, attr_val from [CONTRACT_ATTR] where item_id in (select item_id from [CONTRACT_ATTR] where field_id = 326 and attr_val = 'Y')
       ) sub
 WHERE field_id = 234 or field_id = 413

值A750与制造商表上的item_pk相关联。我想从MFR表中恢复item_name，并将其添加为每个关联的item_id的行。例如，16后将有3行。 MRF中的item_name将位于attr_val列。

我现在最接近的是这是拉入item_name但是在错误的行上，并且正在删除我需要的其他字段。

  SELECT sub.*, m.item_name
  FROM (
Select item_id, field_id, attr_val from [CONTRACT_ATTR] where item_id in (select item_id from [CONTRACT_ATTR] where field_id = 326 and attr_val = 'Y')
       ) sub
JOIN MFR m
ON m.item_pk = sub.attr_val and field_id = 234

我做错了什么以及如何解决？

编辑：

CREATE TABLE [dbo].[CONTRACT_ATTR](
    [ITEM_ID] [int] NOT NULL,
    [FIELD_ID] [int] NOT NULL,
    [ATTR_VAL] [varchar](500) NOT NULL,
    [UPD_DTT] [datetime] NOT NULL,
    [UPD_USR] [varchar](500) NOT NULL,
 CONSTRAINT [PK_CONTRACT_ATTR] PRIMARY KEY CLUSTERED 
(
    [ITEM_ID] ASC,
    [FIELD_ID] ASC,
    [ATTR_VAL] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON)
)

CREATE TABLE [dbo].[MFR](
    [ITEM_ID] [int] IDENTITY(1,1) NOT NULL,
    [ITEM_NAME] [varchar](500) NOT NULL,
    [ADD_DTT] [datetime] NOT NULL,
    [ADD_USR] [varchar](500) NOT NULL,
    [UPD_DTT] [datetime] NOT NULL,
    [UPD_USR] [varchar](500) NOT NULL,
    [ACTIVE_IND] [char](1) NULL,
    [ITEM_PK] [varchar](500) NULL,
 CONSTRAINT [PK_MFR] PRIMARY KEY CLUSTERED 
(
    [ITEM_ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON)
)

Answer 1

您可以使用outer apply()获取制造商名称，然后可选择使用max() over()窗口函数为每item_id返回{@ 1}}，即使field_id不是234 1}}。

select 
    c.item_id
  , c.field_id
  , c.attr_val
  , m.item_name /* includes nulls when c.field_id is not 234 */
  , max(m.item_name) over (partition by c.item_id) as mfr_name
from [CONTRACT_ATTR] c
  outer apply (
    select top 1 i.item_name
    from MFR i
    where i.item_pk = c.attr_val
      and c.field_id = 234
  ) m
where c.item_id in (
  select item_id
  from [CONTRACT_ATTR]
  where field_id = 326 
    and attr_val = 'Y'
 )