如何用UNNEST或任何其他函数展平数组？

Question

假设我得到一个临时表，其中一个字段是一个数组，如何将其转换为多行？

使用PostgreSQL，可以使用UNNEST http://sqlfiddle.com/#!15/21673/19

来完成

WITH x AS (SELECT ARRAY[1,3,2] AS arr)

SELECT UNNEST(arr) FROM x

在BigQuery中运行相同的查询说语法错误：意外 关键字UNNEST在[3：8]

似乎在BigQuery中，UNNEST只能放在FROM子句之后，

然后我尝试了这些：

WITH x AS (SELECT ARRAY[1,3,2] AS arr)

SELECT * FROM UNNEST(x)

这个说 UNNEST不适用于桌子：x在[3:22] ;或者这个

WITH x AS (SELECT ARRAY[1,3,2] AS row)

SELECT * FROM UNNEST(x.arr)

说 UNNEST不适用于桌子：x.arr at [3:22]

BTW，当前临时表x如下所示：

WITH x AS (SELECT ARRAY[1,2] AS row)

SELECT * FROM x
EOF

+--------------+
|     row      |
+--------------+
| [u'1', u'2'] |
+--------------+

虽然我希望把它变成有价值的行：

+-----+
| row |
+-----+
|   1 |
|   2 |
+-----+

https://cloud.google.com/bigquery/sql-reference/arrays

Answer 1

又一个版本 - 涉及“明确的”UNNEST

WITH x AS (SELECT ARRAY[1,3,2] AS arr)
SELECT arr_item FROM x, UNNEST(arr) as arr_item

Answer 2

你可以通过对x的每一行进行arr元素的CROSS JOIN来进行这种展平，即

WITH x AS (SELECT ARRAY[1,3,2] AS arr)
SELECT arr FROM x, x.arr

或者您可以更明确地将其编写为CROSS JOIN，而不是使用逗号

WITH x AS (SELECT ARRAY[1,3,2] AS arr)
SELECT arr FROM x CROSS JOIN x.arr

Answer 3

如果你想按数组创建普通表，你可以在FROM语句中使用UNNEST。

WITH x AS (
  SELECT
    *
  FROM
    UNNEST([1,2,3]) as num
)

select * from x