我想知道以下语法的含义,取自https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#in-operators
(Key1, Key2) IN ( (12,34), (56,78) )
(Key1, Key2) IN ( SELECT (table.a, table.b) FROM table )
当key1的值为12或34且key2的值为56或78时,含义显示行。我是否正确?如果不是简单的例子将有助于理解。
考虑下面的例子
#standardSQL
WITH t AS (
SELECT 1 id, 12 key1, 13 key2 UNION ALL
SELECT 2, 12, 34 UNION ALL
SELECT 3, 56, 57 UNION ALL
SELECT 4, 56, 78
)
SELECT * FROM t
WHERE (key1 = 12 AND key2 = 34)
OR (key1 = 56 AND key2 = 78)
现在你可以重写如下
#standardSQL
WITH t AS (
SELECT 1 id, 12 key1, 13 key2 UNION ALL
SELECT 2, 12, 34 UNION ALL
SELECT 3, 56, 57 UNION ALL
SELECT 4, 56, 78
)
SELECT * FROM t
WHERE (key1, key2) IN ((12,34),(56,78))
这使得它(取决于用户的偏好)更具可读性
在两种情况下输出都是
Row id key1 key2
1 2 12 34
2 4 56 78
语法(key1, key2)
将这两个值组合成一个STRUCT
,然后与另一个STRUCTs进行比较 - (12,34)
和(56,78)
与第二个例子相同
(Key1, Key2) IN ( SELECT (table.a, table.b) FROM table )
从第一个示例中的select语句与常量“获取”合格的结构