Question

我有以下代码，用于计算事件列中出现的内容的次数。

val messages = KafkaUtils
    .createDirectStream[String, String, StringDecoder, StringDecoder]
    (ssc, kafkaParams, topicsSet)

messages
      .map { case (_, jsonRating) => 
        val format = Json.format[AmazonRating]
        val jsValue = Json.parse(record)
        format.reads(jsValue) match {
          case JsSuccess(rating, _) => rating
          case JsError(_) => AmazonRating.empty
      }
      .filter(_ != AmazonRating.empty)
      .foreachRDD(_.foreachPartition(it => recommender.predict(it.toSeq)))

我希望能够像这样计算每一行的百分比。

SELECT event, count(event) as event_count   
FROM event_information
group by event

event   event_count
a       34
b       256
c       45
d       117
e       3

Answer 1

SELECT event, 
       count(event) as event_count,
       count(event) * 100.0 / (select count(*) from event_information) as event_percent
FROM event_information
group by event

Answer 2

大多数SQL方言都支持ANSI标准窗口函数。因此，您可以将查询编写为：

select event, count(*) as event_count,
       count(*) * 100.0/ sum(count(*)) over () as event_percent
from event_information
group by event;

窗口函数通常比子查询和其他方法更有效。

SQL - 计算计数百分比（列）

2 个答案: