Spark SQL “case when” and “when otherwise”

 

Like SQL “case when” statement and Swith statement from popular programming languages, Spark SQL Dataframe also supports similar syntax using “when otherwise” or we can also use “case when” statement. So let’s see an example on how to check for multiple conditions and replicate SQL CASE statement.

• Using “when otherwise” on DataFrame.
• Using “case when” on DataFrame.
• Using && and || operator

First Let’s do the imports that are needed and create spark context and DataFrame.

import org.apache.spark.sql.functions.{when, _}
val spark: SparkSession = SparkSession.builder()
      .master("local[1]")
      .appName("SparkByExamples.com")
      .getOrCreate()

import spark.sqlContext.implicits._
val data = List(("James","","Smith","36636","M",60000),
        ("Michael","Rose","","40288","M",70000),
        ("Robert","","Williams","42114","",400000),
        ("Maria","Anne","Jones","39192","F",500000),
        ("Jen","Mary","Brown","","F",0))

val cols = Seq("first_name","middle_name","last_name","dob","gender","salary")
val df = spark.createDataFrame(data).toDF(cols:_*)

1. Using “when otherwise” on Spark DataFrame.

when is a Spark function, so to use it first we should import using import org.apache.spark.sql.functions.when before. Above code snippet replaces the value of gender with newderived value. when value not qualified with the condition, we are assigning “Unknown” as value.

val df2 = df.withColumn("new_gender", when(col("gender") === "M","Male")
      .when(col("gender") === "F","Female")
      .otherwise("Unknown"))

when can also be used on Spark SQL select statement.

val df4 = df.select(col("*"), when(col("gender") === "M","Male")
      .when(col("gender") === "F","Female")
      .otherwise("Unknown").alias("new_gender"))

2. Using “case when” on Spark DataFrame.

Similar to SQL syntax, we could use “case when” with expression expr() .

val df3 = df.withColumn("new_gender", 
      expr("case when gender = 'M' then 'Male' " +
                       "when gender = 'F' then 'Female' " +
                       "else 'Unknown' end"))

Using within SQL select.

val df4 = df.select(col("*"),
      expr("case when gender = 'M' then 'Male' " +
                       "when gender = 'F' then 'Female' " +
                       "else 'Unknown' end").alias("new_gender"))

3. Using && and || operator

We can also use and (&&) or (||) within when function. To explain this I will use a new set of data to make it simple.

val dataDF = Seq(
      (66, "a", "4"), (67, "a", "0"), (70, "b", "4"), (71, "d", "4"
      )).toDF("id", "code", "amt")
dataDF.withColumn("new_column",
       when(col("code") === "a" || col("code") === "d", "A")
      .when(col("code") === "b" && col("amt") === "4", "B")
      .otherwise("A1"))
      .show()

Output:

+---+----+---+----------+
| id|code|amt|new_column|
+---+----+---+----------+
| 66|   a|  4|         A|
| 67|   a|  0|         A|
| 70|   b|  4|         B|
| 71|   d|  4|         A|
+---+----+---+----------+

Conclusion:

In this article, we have learned how to use spark “case when” using expr() function and “when otherwise” function on Dataframe also, we’ve learned how to use these functions with && and || logical operators. I hope you like this article.

Happy Learning !!