将一列中多行雷同的值只显示在一行

将一列中多行相同的值只显示在一行

数据库环境：SQL SERVER 2008R2

需求如题，左图为初始数据，右图是已实现需求的数据展示

将一列中多行雷同的值只显示在一行

简单说下我的实现思路

1.按id、name排序给原始数据生成行号

2.用递归判断上下行的id是否相等，第一次出现计数器初始值为1，后面再出现则计数器+1

3.对步骤2中生成的结果集再处理，计数器为1的id不变，计数器大于1则id为空字符串

我把实现的代码贴出来

/*准备基础数据*/
WITH    x0
          AS ( SELECT   1 AS id ,
                        'a' AS NAME
               UNION ALL
               SELECT   1 AS id ,
                        'b' AS NAME
               UNION ALL
               SELECT   1 AS id ,
                        'c' AS NAME
               UNION ALL
               SELECT   2 AS id ,
                        'e' AS NAME
               UNION ALL
               SELECT   2 AS id ,
                        'd' AS NAME
               UNION ALL
               SELECT   3 AS id ,
                        'f' AS NAME
               UNION ALL
               SELECT   4 AS id ,
                        'h' AS NAME
               UNION ALL
               SELECT   4 AS id ,
                        'j' AS NAME
             ),/*按id、name排序生成行号*/
        x1
          AS ( SELECT   ROW_NUMBER() OVER ( ORDER BY id, name ) AS tid ,
                        CAST(id AS VARCHAR(2)) id ,
                        name
               FROM     x0
             ),/*递归设置计数器*/
        x2 ( tid, id, name, level )
          AS ( SELECT   tid ,
                        id ,
                        name ,
                        1 AS level
               FROM     x1
               WHERE    tid = 1
               UNION ALL
               SELECT   t1.tid ,
                        t1.id ,
                        t1.NAME ,
                        CASE WHEN t1.id = t2.id THEN level + 1
                             ELSE 1
                        END level
               FROM     x1 t1
                        INNER JOIN x2 t2 ON t1.tid = t2.tid + 1
             )
    /*计数器为1则id不动，否则置为空字符串*/
    SELECT  CASE WHEN level = 1 THEN id
                 ELSE ''
            END id ,
            name
    FROM    x2

先比我的实现，有一网友提供了更简单的实现方式

我们来看一下他是怎么实现的

WITH    x0
          AS ( SELECT   1 AS id ,
                        'a' AS NAME
               UNION ALL
               SELECT   1 AS id ,
                        'b' AS NAME
               UNION ALL
               SELECT   1 AS id ,
                        'c' AS NAME
               UNION ALL
               SELECT   2 AS id ,
                        'e' AS NAME
               UNION ALL
               SELECT   2 AS id ,
                        'd' AS NAME
               UNION ALL
               SELECT   3 AS id ,
                        'f' AS NAME
               UNION ALL
               SELECT   4 AS id ,
                        'h' AS NAME
               UNION ALL
               SELECT   4 AS id ,
                        'j' AS NAME
               UNION ALL
               SELECT   1 AS id ,
                        'j' AS NAME
             )
    SELECT  REPLACE(CASE WHEN ROW_NUMBER() OVER ( PARTITION BY CAST(ID AS VARCHAR(2)) ORDER BY NAME ) <> '1'
                         THEN 0
                         ELSE CAST(ID AS VARCHAR(20))
                    END, 0, '') AS ID ,
            NAME
    FROM    x0

实现的思路和我一样，但他的方法比我的简单，也容易理解。

我相信，实现该需求的方法不局限于这2种，欢迎各位看官提出更多的解题方法。

（本文完）

将一列中多行雷同的值只显示在一行

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