通过查找 Table 替换 SQL 中的列值

Question

我有一个 sql Employee Table 描述了用户对特定金属的喜爱程度，table 看起来像这样

    "Employee_number" "Rank_1  "Rank_2   "Rank_3   "Rank_4   "Rank5
                   1    Gold    null      null      null    null
                   2    bronze  Gold      null      null    null
                   3    Gold    platinum  null      null    null
                   4    Gold    copper    null      null    null
                   5    Gold    bronze    platinum  null    null
                   6    Gold    bronze    platinum  null    null
                   7    Gold    platinum  Silver    null    null
                   8    Gold    platinum  Silver    null    null
                   9    Gold    platinum  business  null    null
                   10   null    null      null      null    null
                   11   Silver  bronze    business  platinum Gold

Employee_number字段是唯一字段，

还有一个table描述了金属的一般排名，它看起来像这样：

Metal     Rank
Gold        1
platinum    2
silver      3
copper      4
bronze      5

我想做的是，每当员工有空值时，根据他们的排名填写默认金属

例如 -> 对于员工 10：所有值均为空，简单，他的 rank_1 金属将是黄金，rank2_metal 将是白金，rank3_metal 将是白银，排名 4_metal 将是铜牌，排名 5_metal 将是青铜牌

现在 employee_1，他已经有了 rank_1 金属，但没有其他等级可用，所以用白金替换 rank2_metal，用银替换 rank_3 金属， rank_4 金属与铜，rank_5 金属与青铜

现在 employee_2，他的第一金属是青铜，第二金属是金，他的 rank3_metal 是白金，rank_4 金属是银，排名5_metal 将是铜

相似，让我们以 employee_6 的情况为例，他已经填充了三个等级，需要填充等级 4 和 5，他的 rank_4 金属将是银，而 rank_5 金属将是铜

有没有人对 sql 中的一个有任何建议，我正在使用 bigquery

Answer 1

以下适用于 BigQuery 标准 SQL - 希望您将其用于您的实际用例。

#standardSQL
WITH metals AS (
  SELECT 'Gold' Metal, 1 RANK UNION ALL SELECT 'platinum', 2 UNION ALL
  SELECT 'silver', 3 UNION ALL SELECT 'copper', 4 UNION ALL SELECT 'bronze', 5 
)
SELECT Employee_number, 
  MAX(IF(pos=0, Metal, NULL)) Rank_1,
  MAX(IF(pos=1, Metal, NULL)) Rank_2,
  MAX(IF(pos=2, Metal, NULL)) Rank_3,
  MAX(IF(pos=3, Metal, NULL)) Rank_4,
  MAX(IF(pos=4, Metal, NULL)) Rank_5
FROM (
  SELECT Employee_number,
    ARRAY_CONCAT(
      ARRAY(SELECT Metal FROM (
          SELECT 1 a, Rank_1 Metal UNION ALL SELECT 2, Rank_2 UNION ALL 
          SELECT 3, Rank_3 UNION ALL SELECT 4, Rank_4 UNION ALL 
          SELECT 5, Rank_5 )
        WHERE NOT Metal IS NULL
        ORDER BY a
      ), ARRAY(SELECT Metal FROM metals m
        WHERE NOT LOWER(Metal) IN (
          SELECT x FROM UNNEST(ARRAY(
            SELECT LOWER(b) FROM (
              SELECT Rank_1 b UNION ALL SELECT Rank_2 UNION ALL
              SELECT Rank_3 UNION ALL SELECT Rank_4 UNION ALL
              SELECT Rank_5 )
            WHERE NOT b IS NULL
          )) x
        ) ORDER BY RANK
      )) arr
  FROM `project.dataset.employee`
), UNNEST(arr) Metal WITH OFFSET pos  
GROUP BY Employee_number
ORDER BY Employee_number

您可以使用您问题中的虚拟数据进行测试，如下所示

#standardSQL
WITH `project.dataset.employee` AS (
  SELECT 1 Employee_number, 'Gold' Rank_1, NULL Rank_2, NULL Rank_3, NULL Rank_4, NULL Rank_5 UNION ALL
  SELECT 2, 'bronze', 'Gold', NULL, NULL, NULL UNION ALL
  SELECT 3, 'Gold', 'platinum', NULL, NULL, NULL UNION ALL
  SELECT 4, 'Gold', 'copper', NULL, NULL, NULL UNION ALL
  SELECT 5, 'Gold', 'bronze', 'platinum', NULL, NULL UNION ALL
  SELECT 6, 'Gold', 'bronze', 'platinum', NULL, NULL UNION ALL
  SELECT 7, 'Gold', 'platinum', 'Silver', NULL, NULL UNION ALL
  SELECT 8, 'Gold', 'platinum', 'Silver', NULL, NULL UNION ALL
  SELECT 9, 'Gold', 'platinum', 'business', NULL, NULL UNION ALL
  SELECT 10, NULL, NULL, NULL, NULL, NULL UNION ALL
  SELECT 11, 'Silver', 'bronze', 'business', 'platinum',  'Gold' 
), metals AS (
  SELECT 'Gold' Metal, 1 RANK UNION ALL SELECT 'platinum', 2 UNION ALL
  SELECT 'silver', 3 UNION ALL SELECT 'copper', 4 UNION ALL SELECT 'bronze', 5 
)
SELECT Employee_number, 
  MAX(IF(pos=0, Metal, NULL)) Rank_1,
  MAX(IF(pos=1, Metal, NULL)) Rank_2,
  MAX(IF(pos=2, Metal, NULL)) Rank_3,
  MAX(IF(pos=3, Metal, NULL)) Rank_4,
  MAX(IF(pos=4, Metal, NULL)) Rank_5
FROM (
  SELECT Employee_number,
    ARRAY_CONCAT(
      ARRAY(SELECT Metal FROM (
          SELECT 1 a, Rank_1 Metal UNION ALL SELECT 2, Rank_2 UNION ALL 
          SELECT 3, Rank_3 UNION ALL SELECT 4, Rank_4 UNION ALL 
          SELECT 5, Rank_5 )
        WHERE NOT Metal IS NULL
        ORDER BY a
      ), ARRAY(SELECT Metal FROM metals m
        WHERE NOT LOWER(Metal) IN (
          SELECT x FROM UNNEST(ARRAY(
            SELECT LOWER(b) FROM (
              SELECT Rank_1 b UNION ALL SELECT Rank_2 UNION ALL
              SELECT Rank_3 UNION ALL SELECT Rank_4 UNION ALL
              SELECT Rank_5 )
            WHERE NOT b IS NULL
          )) x
        ) ORDER BY RANK
      )) arr
  FROM `project.dataset.employee`
), UNNEST(arr) Metal WITH OFFSET pos  
GROUP BY Employee_number
ORDER BY Employee_number

结果

Row Employee_number Rank_1  Rank_2      Rank_3      Rank_4      Rank_5   
1   1               Gold    platinum    silver      copper      bronze   
2   2               bronze  Gold        platinum    silver      copper   
3   3               Gold    platinum    silver      copper      bronze   
4   4               Gold    copper      platinum    silver      bronze   
5   5               Gold    bronze      platinum    silver      copper   
6   6               Gold    bronze      platinum    silver      copper   
7   7               Gold    platinum    Silver      copper      bronze   
8   8               Gold    platinum    Silver      copper      bronze   
9   9               Gold    platinum    business    silver      copper   
10  10              Gold    platinum    silver      copper      bronze   
11  11              Silver  bronze      business    platinum    Gold

注意：以上解决方案假设填充金属和 NULL 金属之间没有混合，这意味着三个选项：

1. all Rank fields filled already with Metal  
2. all Rank fields are NULL
3. first 1 or more fields filled with Metal and rest are NULLs

话虽如此，第一个数组是由填充字段构成的；第二个数组由 Metals table 的其余 Metal 字段构建而成；然后连接两个数组，前 5 个元素用于重新创建原始 table

希望不要太乱

P.S。上面的解决方案可以相对容易地扩展到 NULL 和填充金属混合使用的情况 - 但看起来这超出了问题的范围 :o)

通过查找 Table 替换 SQL 中的列值

Replace Column Values in SQL from a lookup Table

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google-bigquery

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