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Apache Spark ???? Null ? ??
? ??? ??? MySQL ???? Apache Spark ?? ?? Null ?? ????? ??? ?? ????

Apache Spark ?? ?? Null ?? ????? ??? ?? ????

Dec 31, 2024 pm 05:36 PM

How Can I Preserve Null Values During Apache Spark Joins?

Apache Spark ???? Null ? ??

????? Apache Spark? ??? ??? ? Null ?? ?? ?? ?????. ?? ??? ??? ?? ???? ?? Spark? ?? ??? ?????.

NULL ?? ?? ???(<=>)

Spark 1.6??? ?? NULL? ??????. - ??? null ?? ??? ? ?? ??? ?? ??? ??.

numbersDf
  .join(lettersDf, numbersDf("numbers") <=> lettersDf("numbers"))
  .drop(lettersDf("numbers"))

Column.eqNullSafe(PySpark 2.3.0 )

PySpark 2.3.0 ????? Column.eqNullSafe? ???? NULL? ??? ? ????. ??? ?? 

numbers_df = sc.parallelize([
    ("123", ), ("456", ), (None, ), ("", )
]).toDF(["numbers"])

letters_df = sc.parallelize([
    ("123", "abc"), ("456", "def"), (None, "zzz"), ("", "hhh")
]).toDF(["numbers", "letters"])

numbers_df.join(letters_df, numbers_df.numbers.eqNullSafe(letters_df.numbers))

%<=>% (SparkR)

SparkR? NULL ?? ?? ??? ?? %<=>% ???? ?????. .

numbers_df <- createDataFrame(data.frame(numbers = c("123", "456", NA, "")))
letters_df <- createDataFrame(data.frame(
  numbers = c("123", "456", NA, ""),
  letters = c("abc", "def", "zzz", "hhh")
))

head(join(numbers_df, letters_df, numbers_df$numbers %<=>% letters_df$numbers))

??? ??? ????. (SQL)

SQL(Spark 2.2.0 )??? IS NOT DISTINCT FROM? ???? ???? Null ?? ??? ? ????.

SELECT * FROM numbers JOIN letters 
ON numbers.numbers IS NOT DISTINCT FROM letters.numbers

? ???? ??? ? ????. DataFrame API ??:

numbersDf.alias("numbers")
  .join(lettersDf.alias("letters"))
  .where("numbers.numbers IS NOT DISTINCT FROM letters.numbers")

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