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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MySQL? ? ????? ??? ??? ????? ?? ?? ??? ?? ???????. 1. Windows ??? : MySQL ?? ?????? ? ??? ????? (?? ??? ????? C : \ programfiles \ mysql \ mysqlserverx.x \ bin), "? ???"→ "??"→ "Advanced System ??"→ "?? ??", "??? ??", MySQlb in wors in mysqlb in wors in mysqlb in world in that the the the the the seel worl ?? ????? ?? ???? MySQL? ??????-Version Versification; 2.Macos ? Linux ??? : Bash ??? ?? ~/.bashrc ?? ~/.bash_

MySQLDump? MySQL ??????? ??? ??? ???? ???? ?????. ??????? ???? ?? ?? ? ?? ?? ???? SQL ??? ?????. 1. ?? ??? ????? ??? ?????? ??? ???? ??? SQL ???? ?????. 2. ??? ?????? ?? ??? ??? ???? TB ?? ???? ?? ???? ???? ????. 3. ???? ???-single transaction,-databases,-all-databases,-routines ?; 4. MySQL ??? ???? ?? ?? ?? ?? ?? ? ??? ?? ??? ???? ? ????. 5. ??? ????? ????? ?? ? ?? ??? ???? ?? ????.

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