sql With As 递归实现树形结构数据初始化

今天遇到一个问题记录下，我们需要导入其他系统的树形结构数据，但是我们这边的层级是要以 父级.子级.子级 这样的Code 才能实现，而对方给到的数据却是以当前编码和父级编码这样的数据给到我们，所以只能对编码做点改造，话不多说，直接上图，下面为待整理的数据

--对方表结构
CREATE TABLE [dbo].[PARAM_PARAM]
(
	[ID]				[CHAR](12),
	[PARENTID]		[CHAR](12),
	[CLASSID]		[CHAR](5),
	[GROUPID]		[CHAR](6),
	[CODE]			[VARCHAR](255),
	[NAME]			[VARCHAR](255),
	[VALID]			[CHAR](1),
	[DESCRIPTION]	[VARCHAR](1000),
	[BRIEFNAME]		[VARCHAR](255),
	[UPDATEDATE]	[DATE],
	[USERID]			[VARCHAR](40),
	[DISPLAYORDER] [VARCHAR](255)
);
GO

对方数据插入后的显示效果

分析：只要是树形结构的一般都会有这两个列，一个是当前节点Code 一个是父级节点Code，我们只需要递归去刷一下Code和名称就可以实现，代码如下。

WITH child (CODE, NAME, DISPLAYORDER, PARENTID, level, newCode, newName, parentCode)
	AS (
		SELECT
				CODE,
				NAME,
				DISPLAYORDER,
				PARENTID,
				1 AS level,
				CONVERT (VARCHAR(100), CODE) AS newCode,
				CONVERT (VARCHAR(300), NAME) AS newName,
				CODE AS parentCode
		FROM	PARAM_PARAM
		WHERE DISPLAYORDER = '000000021348' --最顶级编码
		UNION ALL
		SELECT
				a.CODE,
				a.NAME,
				a.DISPLAYORDER,
				a.PARENTID,
				b.level + 1,
				CONVERT (VARCHAR(100), b.newCode + '.' + a.CODE) AS newCode,
				CONVERT (VARCHAR(300), b.newName + '-' + a.NAME) AS newName,
				b.CODE AS parentCode
		FROM	dbo.PARAM_PARAM a
				INNER JOIN child b ON a.PARENTID = b.DISPLAYORDER
		)
SELECT
			*
FROM		child
ORDER BY child.CODE;
--注意：用with语法，后面执行查询时必须要把当前表查询出来

效果如下

如果表有 IfEnd 字段，那么根据如下代码即可查询出来

WITH child (CODE, NAME, DISPLAYORDER, PARENTID, level, newCode, newName, parentCode, IfEnd)
	AS (
		SELECT
				CODE,
				NAME,
				DISPLAYORDER,
				PARENTID,
				1 AS level,
				CONVERT (VARCHAR(100), CODE) AS newCode,
				CONVERT (VARCHAR(300), NAME) AS newName,
				CODE AS parentCode,
				0 AS IfEnd
		FROM	PARAM_PARAM
		WHERE DISPLAYORDER = '000000021348' --最顶级编码
		UNION ALL
		SELECT
				a.CODE,
				a.NAME,
				a.DISPLAYORDER,
				a.PARENTID,
				b.level + 1,
				CONVERT (VARCHAR(100), b.newCode + '.' + a.CODE) AS newCode,
				CONVERT (VARCHAR(300), b.newName + '-' + a.NAME) AS newName,
				b.CODE AS parentCode,
				IfEnd = (CASE
								WHEN	EXISTS
										(	SELECT
															1
												FROM		dbo.PARAM_PARAM 
												WHERE		PARENTID = a.DISPLAYORDER) THEN
									0
								ELSE 1
							END)
		FROM	dbo.PARAM_PARAM a
				INNER JOIN child b ON a.PARENTID = b.DISPLAYORDER
		)
SELECT
			*
FROM		child
ORDER BY child.CODE;

结果

查询当前所有父级节点

SELECT
		*
FROM	Tree A
WHERE NOT EXISTS
	(	SELECT
				*
		FROM	Tree B
		WHERE A.ParentCode = B.Code);

查询当前所有末级节点

SELECT
		*
FROM	Tree A
WHERE NOT EXISTS
	(	SELECT
				*
		FROM	Tree B
		WHERE A.Code = B.ParentCode);