如果在Spark SQL中不存在其他更新，则进行插入

问题描述

在Spark SQL中是否有进行如果不存在则进行更新的插入操作"的规定.

Is there any provision of doing "INSERT IF NOT EXISTS ELSE UPDATE" in Spark SQL.

我有Spark SQL表"ABC"，其中包含一些记录.然后我还有另一笔记录，我想根据它们是否存在于此表中在此表中插入/更新.

I have Spark SQL table "ABC" that has some records.And then i have another batch of records that i want to Insert/update in this table based on whether they exist in this table or not.

有没有我可以在SQL查询中使用的SQL命令来实现这一目标?

is there a SQL command that i can use in SQL query to make this happen?

推荐答案

在常规Spark中，可以通过join后跟map这样的方式来实现:

In regular Spark this could be achieved with a join followed by a map like this:

import spark.implicits._
val df1 = spark.sparkContext.parallelize(List(("id1", "orginal"), ("id2", "original"))).toDF("df1_id", "df1_status")
val df2 = spark.sparkContext.parallelize(List(("id1", "new"), ("id3","new"))).toDF("df2_id", "df2_status")

val df3 = df1
  .join(df2, 'df1_id === 'df2_id, "outer")
  .map(row => {
    if (row.isNullAt(2))
      (row.getString(0), row.getString(1))
    else
      (row.getString(2), row.getString(3))
  })

这将产生:

scala> df3.show
+---+--------+
| _1|      _2|
+---+--------+
|id3|     new|
|id1|     new|
|id2|original|
+---+--------+

您也可以将select与udfs一起使用，而不是map，但是在这种特殊情况下使用空值的情况下，我个人更喜欢使用map变体.

You could also use select with udfs instead of map, but in this particular case with null-values, I personally prefer the map variant.

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