SQL Server等效于Oracle的"CONNECT BY PRIOR"和"ORDER SIBLINGS BY"

Question

我有这个Oracle代码结构,我正在尝试转换为SQL Server 2008 (注意:我在方括号'[]'中使用了通用名称,封闭的列名和表名,并做了一些格式化以使代码更多可读):

SELECT [col#1], [col#2], [col#3], ..., [col#n], [LEVEL] 
FROM (SELECT [col#1], [col#2], [col#3], ..., [col#n] 
      FROM [TABLE_1] 
      WHERE ... ) 
CONNECT BY PRIOR [col#1] = [col#2] 
START WITH [col#2] IS NULL 
ORDER SIBLINGS BY [col#3]

什么是上述代码的SQL Server等效模板？

具体来说,我正在努力与LEVEL和'ORDER SIBLINGS BY'Oracle构造.

注意: 上面的"代码"是一组Oracle过程的最终输出.基本上,'WHERE'子句是动态构建的,并根据传递的各种参数而变化.以"CONNECT BY PRIOR"开头的代码块是硬编码的.

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以供参考:

SQL SERVER文章中关于ORACLE的连接的模拟很接近,但它没有解释如何处理'LEVEL'和'ORDER SIBLINGS'结构.......我的思绪在变化!

SELECT name 
  FROM emp
  START WITH name = 'Joan'
  CONNECT BY PRIOR empid = mgrid

相当于:

WITH n(empid, name) AS 
   (SELECT empid, name 
    FROM emp
    WHERE name = 'Joan'
        UNION ALL
    SELECT nplus1.empid, nplus1.name 
    FROM emp as nplus1, n
    WHERE n.empid = nplus1.mgrid)
SELECT name FROM n

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如果我有一个初始模板可供使用,它将帮助我构建SQL Server存储过程以构建正确的T-SQL语句.

非常感谢协助.

Answer 1

模拟LEVEL列

通过递增递归部分中的计数器可以轻松地模拟级别列:

WITH tree (empid, name, level) AS  (
  SELECT empid, name, 1 as level
  FROM emp
  WHERE name = 'Joan'

  UNION ALL

  SELECT child.empid, child.name, parent.level + 1
  FROM emp as child
    JOIN tree parent on parent.empid = child.mgrid
)
SELECT name 
FROM tree;

模拟 order siblings by

模拟order siblings by它有点复杂.假设我们有一个列sort_order定义每个父元素的顺序(不是整体排序顺序 - 因为那时order siblings没有必要),那么我们可以创建一个列,它给出了一个整体排序顺序:

WITH tree (empid, name, level, sort_path) AS  (
  SELECT empid, name, 1 as level, 
         cast('/' + right('000000' + CONVERT(varchar, sort_order), 6) as varchar(max))
  FROM emp
  WHERE name = 'Joan'

  UNION ALL

  SELECT child.empid, child.name, parent.level + 1, 
         parent.sort_path + '/' + right('000000' + CONVERT(varchar, child.sort_order), 6) 
  FROM emp as child
    JOIN tree parent on parent.empid = child.mgrid
)
SELECT * 
FROM tree
order by sort_path;

sort_path外观的表达式如此复杂,因为SQL Server(至少是您使用的版本)没有简单的函数来格式化带前导零的数字.在Postgres中,我将使用整数数组,以便varchar不需要转换- 但这在SQL Server中也不起作用.