如何表达2阶段循环T-SQL SELECT查询？

Question

这是一个SQL专家的问题!

我正在使用SQL SERVER 2008 R2 Express.

我有一个名为[myTable]由两种类型的记录组成的表.

第一类记录是主记录,第二类[Relative]记录是记录.

每条主记录可能有几条相关记录.

我想SLELECT TOP 10 * FROM [myTable]掌握的记录,并结合分的记录,像SELECT TOP 4的[Relative]每个记录.

每条记录都有一[PKID] NO NULL IDENTITY(1,1) PRIMARY KEY CLUSTERED列.

我想我需要这样的东西:

SELECT TOP 10 * FROM [myTable]  WHERE [Relative]=0 
UNION
For each (SELECT TOP 10 [PKID] as Master, * FROM [myTable] WHERE [Relative]=0 )
{SELECT TOP 4 * FROM [myTable] WHERE [Relative] = Master}

我应该如何纠正查询以实现我的目标？

我有一个次要问题,我怀疑它有一个简单的解决方案:

相对记录有两种风格,如专栏所述[IsImportant].

有没有办法确保每个主记录只选择一条重要的相对记录？

有没有办法跳过主记录,如果它有少于4个相对记录,而其中只有1个是重要的？

Answer 1

编辑

这是对您的要求的正确解释吗？

[myTable]有3个相关领域......

• PKID:每行的唯一标识符
• relative:行的父级的PKID(如果该行没有父级,则为0 [AKA - 主服务器])

• IsImportant:0/1标志

  1. 返回不超过10个主记录
  2. 对于每个主记录,返回不超过4个相对记录
  3. 在4个相对记录中,返回不超过1个IsImportant记录
  4. 跳过任何少于4个亲戚的主人(将所有IsImportant视为1)

问题:
- 如果一个主人有3个相对记录,而且没有一个是重要的,那么还是跳过？
- 如果一个主人有4个相对记录,并且多于1是重要的,还是跳过？

最佳猜测答案......

WITH
  master_metadata
AS
(
  SELECT
    relative         AS MasterID,
    COUNT(*)         AS Relatives,
    SUM(isImportant) AS IsImportantRelatives
  FROM
    [myTable]
  WHERE
    relative <> 0
  GROUP BY
    relative
  HAVING
    COUNT(*) - SUM(isImportant) + MAX(isImportant) >= 4
)
,
  master
AS
(
  SELECT TOP 10
    NULL AS sequence_id,
    [myTable].*,
    [master_metadata].Relatives,
    [master_metadata].IsImportantRelatives
  FROM
    [myTable]
  INNER JOIN
    [master_metadata]
      ON [master_metadata].MasterID = [myTable].PKID
  ORDER BY
    [myTable].Selector
)
,
  relative
AS
(
  SELECT
    ROW_NUMBER() OVER (PARTITION BY relative, IsImportant ORDER BY Selector)  AS sequence_id,
    *
  FROM
    [myTable]
)
,
  data
AS
(
  SELECT
    PKID AS MasterID,
    *
  FROM
    [master]

  UNION ALL

  SELECT
    [master].PKID AS MasterID,
    [relative].*, Relatives, IsImportantRelatives
  FROM
    [master]
  INNER JOIN
    [relative]
      ON  ([relative].relative = [master].PKID)
      AND (  ([relative].isImportant = 1 AND [relative].sequence_id  = 1)
          OR ([relative].isImportant = 0 AND [relative].sequence_id <= 3)
          OR ([relative].isImportant = 0 AND [relative].sequence_id  = 4 AND [master].IsImportantRelatives = 0)
          )
)

SELECT
  *
FROM
  [data]
ORDER BY
  MasterID,
  CASE WHEN MasterID = PKID THEN 0 ELSE 1 END,
  IsImportant DESC,
  relative