如何在Spark SQL中计算合计的百分比

Question

考虑以下数据：

Name | Flag
A    | 0
A    | 1
A    | 0
B    | 0
B    | 1
B    | 1

我想把它转换成：

Name | Total | With Flag | Percentage
A    | 3     | 1         | 33%
B    | 3     | 2         | 66%

最好是在Spark SQL中。

Answer 1

例如：

val df = sc.parallelize(Seq(
  ("A", 0), ("A", 1), ("A", 0),
  ("B", 0), ("B", 1), ("B", 1)
)).toDF("Name", "Flag")
df.groupBy($"Name").agg(
  count("*").alias("total"),
  sum($"flag").alias("with_flag"),
  // Do you really want to truncate not for example round?
  mean($"flag").multiply(100).cast("integer").alias("percentage"))
// +----+-----+---------+----------+
// |name|total|with_flag|percentage|
// +----+-----+---------+----------+
// |   A|    3|        1|        33|
// |   B|    3|        2|        66|
// +----+-----+---------+----------+

或：

df.registerTempTable("df")
sqlContext.sql("""
  SELECT name, COUNT(*) total, SUM(flag) with_flag, 
         CAST(AVG(flag) * 100 AS INT) percentage
  FROM df
  GROUP BY name""")
// +----+-----+---------+----------+
// |name|total|with_flag|percentage|
// +----+-----+---------+----------+
// |   A|    3|        1|        33|
// |   B|    3|        2|        66|
// +----+-----+---------+----------+