Question

我有一个包含多个重复字段的模式，这些字段都是记录类型。例如，架构是这样的：

name: string,

class: record(repeated),

class.id :string

class.title: string,

school: record(repeated),

school.id: string,

school.title: string.

如何在标准SQL中查询并返回带有班级和学校列表的学生行（班级和学校完全无关）。

实际上，一个简单的SELECT *可以工作，但我想选择每一列并重命名它们，即SELECT name作为student_name，classes，schools。我还想过滤一些类和学校，即只显示满足某些约束的类。

示例：name：'Tom'，class：[{id：1，title：math}，{id：2，title：physics}，{id：3，title：math}]，school：[{id ：1，title：Yale}，{id：2，title：Havard}，{id：3，title：Yale}] 我想通过class.title和school.title过滤返回如下行：name：'Tom'，class：[{id：1，title：math}，{id：3，title：math}]，school ：[{id：1，title：Yale}，{id：3，title：Yale}]

Answer 1

以下是BigQuery Standard SQL

#standardSQL
SELECT name as student_name, 
  ARRAY(SELECT AS STRUCT * FROM UNNEST(class) class WHERE class.title = 'math') classes,
  ARRAY(SELECT AS STRUCT * FROM UNNEST(school) school WHERE school.title = 'Yale') schools
FROM `yourproject.yourdataset.yourtable`

您可以使用问题中的虚拟数据来测试/播放上面的内容：

#standardSQL
WITH `yourproject.yourdataset.yourtable` AS (
  SELECT 
    'Tom' name, 
    [
      STRUCT(1 AS id, 'math' AS title), 
      (2, 'physics'), 
      (3, 'math')
    ] class, 
    [
      STRUCT(1 AS id, 'Yale' AS title), 
      (2, 'Havard'), 
      (3, 'Yale')
    ] school 
)
SELECT name as student_name, 
  ARRAY(SELECT AS STRUCT * FROM UNNEST(class) class WHERE class.title = 'math') classes,
  ARRAY(SELECT AS STRUCT * FROM UNNEST(school) school WHERE school.title = 'Yale') schools
FROM `yourproject.yourdataset.yourtable`

结果如下

name    class.id    class.title school.id   school.title     
Tom     1           math        1           Yale     
        3           math        3           Yale

上面应该让您了解如何在重复字段内过滤

包含2个重复字段的查询表

1 个答案: