返回包含映射键的无序数组。
Syntax
from pyspark.sql import functions as sf
sf.map_keys(col)
参数
| 参数 | 类型 | Description |
|---|---|---|
col |
pyspark.sql.Column 或 str |
列或表达式的名称 |
退货
pyspark.sql.Column：映射的键作为数组。
例子
示例 1：从简单映射中提取密钥
from pyspark.sql import functions as sf
df = spark.sql("SELECT map(1, 'a', 2, 'b') as data")
df.select(sf.sort_array(sf.map_keys("data"))).show()
+--------------------------------+
|sort_array(map_keys(data), true)|
+--------------------------------+
| [1, 2]|
+--------------------------------+
示例 2：使用复杂键从映射中提取键
from pyspark.sql import functions as sf
df = spark.sql("SELECT map(array(1, 2), 'a', array(3, 4), 'b') as data")
df.select(sf.sort_array(sf.map_keys("data"))).show()
+--------------------------------+
|sort_array(map_keys(data), true)|
+--------------------------------+
| [[1, 2], [3, 4]]|
+--------------------------------+
示例 3：从空映射中提取密钥
from pyspark.sql import functions as sf
df = spark.sql("SELECT map() as data")
df.select(sf.map_keys("data")).show()
+--------------+
|map_keys(data)|
+--------------+
| []|
+--------------+