在同一个表中连接由分隔符分隔的列答案

【问题标题】：join columns separated by delimiter in same table在同一个表中连接由分隔符分隔的列
【发布时间】：2020-08-22 17:09:49
【问题描述】：

我有以下数据集

color_code   fav_color_code    color_code_name    fav_color_name 
1|2          5                 blue|white         black
3|4          7|9               green|red          pink|yellow

我需要将join 的第一个值color_code 转换为color_code_name 的第一个值，将color_code 的第二个值转换为color_code_name 的第二个值等等。

code                color
1                   blue
2                   white
5                   black
3                   green
4                   red
7                   pink
9                   yellow

我正在使用下面的代码，但它正在交叉连接，因为我没有 id 到 join。如果我映射 2 列而不是多列，则此代码有效。

有人可以帮我得到预期的结果吗？

SELECT 
        t1.code AS code, 
        t2.color AS color, 
      FROM 
        (
          SELECT 
            c.value :: varchar AS code, 
            row_number() over(
              order by 
                code
            ) AS rownum 
          FROM 
            table, 
            lateral flatten (
              input => split(color_code, '|')
            ) c  
          UNION 
          SELECT 
            d.value :: varchar AS code, 
            row_number() OVER(
              ORDER BY 
                code
            ) AS rownum
            FROM 
            table, 
            lateral flatten (
              input => split(fav_color_code, '|')
            ) d 
        ) t1 
        JOIN (
          SELECT 
            f.value :: varchar AS color, 
            row_number() OVER(
              ORDER BY 
                color
            ) AS rownum 
          FROM 
            table, 
            lateral flatten (
              input => split(color_code_name, '|')
            ) f 
          UNION 
          SELECT 
            g.value :: varchar AS color, 
            row_number() OVER(
              ORDER BY 
                color
            ) AS rownum 
          FROM 
            table, 
            lateral flatten (
              input => split(fav_color_name, '|')
            ) g 
        ) t2 ON (t1.rownum = t2.rownum) 
      ORDER BY 
        t1.color

【问题讨论】：

标签： sql join union comma

【解决方案1】：

出于解释的目的，您可以分几个步骤遵循这种方法，因为我认为一个步骤是一团糟。

注意： 代码解决方案是在Hive中完成的（post没有指定任何sql-query-engine），但是在Hive中几乎所有东西都是sql-standard。

原始数据

+--------------------+------------------------+-------------------------+------------------------+--+
| colors.color_code  | colors.fav_color_code  | colors.color_code_name  | colors.fav_color_name  |
+--------------------+------------------------+-------------------------+------------------------+--+
| 1|2                | 5                      | blue|white              | black                  |
| 3|4                | 7|9                    | green|red               | pink|yellow            |
+--------------------+------------------------+-------------------------+------------------------+--

首先，我们创建一个temp table 和color ids，其中我们将code columns、split 列连接成一个array，然后explode array 和一个rownumber

CREATE TABLE tc1 AS
SELECT ROW_NUMBER() OVER() AS rownum, CAST(color_id AS INT) as color_id
FROM colors
LATERAL VIEW EXPLODE(SPLIT(CONCAT(color_code,'|', fav_color_code),'\\|')) a1 AS color_id;

我们使用color names 创建第二个temp table，并按照以前的方法，但现在我们将color_name 列、split 列连接成array，然后将explode 连接到array带有rownumber

CREATE TABLE tc2 AS
SELECT ROW_NUMBER() OVER() AS rownum, color_name
FROM colors
LATERAL VIEW EXPLODE(SPLIT(CONCAT(color_code_name,'|', fav_color_name),'\\|')) a1 AS color_name;

我们 joinrownum 的临时表

SELECT color_id, color_name
FROM tc1
JOIN tc2 ON(tc1.rownum = tc2.rownum)
ORDER BY color_id;

预期输出

+-----------+-------------+--+
| color_id  | color_name  |
+-----------+-------------+--+
| 1         | blue        |
| 2         | white       |
| 3         | green       |
| 4         | red         |
| 5         | black       |
| 7         | pink        |
| 9         | yellow      |
+-----------+-------------+--+

一次性做同样的事情，虽然不是一个轻量级的查询

SELECT tc1.color_id, tc2.color_name
FROM (SELECT ROW_NUMBER() OVER() AS rownum, CAST(color_id AS INT) as color_id
      FROM colors
      LATERAL VIEW EXPLODE(SPLIT(CONCAT(color_code,'|', fav_color_code),'\\|')) a1 AS color_id) AS tc1
JOIN (SELECT ROW_NUMBER() OVER() AS rownum, color_name
      FROM colors
      LATERAL VIEW EXPLODE(SPLIT(CONCAT(color_code_name,'|', fav_color_name),'\\|')) a1 AS color_name) AS tc2
ON(tc1.rownum = tc2.rownum)
ORDER BY tc1.color_id;

预期输出

+---------------+-----------------+--+
| tc1.color_id  | tc2.color_name  |
+---------------+-----------------+--+
| 1             | blue            |
| 2             | white           |
| 3             | green           |
| 4             | red             |
| 5             | black           |
| 7             | pink            |
| 9             | yellow          |
+---------------+-----------------+--+

【讨论】：