pyspark sql：AttributeError：'NoneType'对象没有属性'join'

Question

def main(inputs, output):

    sdf = spark.read.csv(inputs, schema=observation_schema)
    sdf.registerTempTable('filtertable')

    result = spark.sql("""
    SELECT * FROM filtertable WHERE qflag IS NULL
    """).show()

    temp_max = spark.sql(""" SELECT date, station, value FROM filtertable WHERE (observation = 'TMAX')""").show()
    temp_min = spark.sql(""" SELECT date, station, value FROM filtertable WHERE (observation = 'TMIN')""").show()

    result = temp_max.join(temp_min, condition1).select(temp_max('date'), temp_max('station'), ((temp_max('TMAX')-temp_min('TMIN'))/10)).alias('Range'))

错误：

Traceback (most recent call last):
  File "/Users/syedikram/Documents/temp_range_sql.py", line 96, in <module>
    main(inputs, output)
  File "/Users/syedikram/Documents/temp_range_sql.py", line 52, in main
    result = temp_max.join(temp_min, condition1).select(temp_max('date'), temp_max('station'), ((temp_max('TMAX')-temp_min('TMIN')/10)).alias('Range'))
AttributeError: 'NoneType' object has no attribute 'join'

在联接操作上执行会给我带来Nonetype对象错误。联机查找无济于事，因为pyspark sql的在线文档很少。我在这里做错了什么？

Answer 1

.show()从中删除from temp_max，temp_min因为它show仅输出一个字符串并且不返回任何内容（因此得到AttributeError: 'NoneType' object has no attribute 'join'）。