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Sparkbox select how to#

Sparkbox select how to#

How to provide a new name to column using AS /ALIAS.Disclosure: If you make a purchase through the links posted below, I may receive a small compensation.

What are columns of String type and Instance of Class Type.

Various ways in which columns can be referred in Spark Dataframe.

How to refer columns in Spark Dataframe.

Lets check it wit an example val dfTN = Seq(("Smith",45),("Andy",77)).toDF("Name","Marks") ĭfTN.selectExpr("Name", "Marks + 5 as newMarks" ).show If you are comfortable with SQL and want to write the columns and expressions similar to SQL then selectExpr is for you.

To provide a new name we need to use AS or ALIAS.

If you notice, in the output Spark shows the column name as “Marks + 5” which is not the ideal way of displaying a column. val dfTN = Seq(("Smith",45),("Andy",77)).toDF("Name","Marks") Įrror: overloaded method value select with alternatives:Īs you see above when we tried to mix the column types “String” and ‘Column ,spark immediately threw an error. One thing to notice here is while using Select we should not mix both types. Also, we have understood till now that the columns are of String or Column Type. The syntax is pretty straight forward df.select(). Next, lets learn about Select SPARK Dataframe selectĪs seen before we use SELECT to fetch all are selected columns from a dataframe.When we refer column as an instance of Column Class we are able to use expressions.In Line 18 we have to import .functions._ before we use column functions.When Column type is string we cannot perform any expressions.To resolve this we need to refer column asĭfTN.select(col("Name"),col("Marks") + 5).showĭfTN.select(column("Name"),column("Marks") + 5).show AnalysisException: cannot resolve '`Marks5`' given input columns: Lets add 5 marks to each student String Column Type If you want to have some expressions on your columns then you have to refer the column as an instance of Column Class. $/ ‘(tick) – $(“col_nm”) / ‘col_nm This is syntatic sugar to show column class in scala.Īs you notice there are basically 2 ways in which you can refer a column, either through String or a Column Class.column/col – column(“col_nm”)/col(“col_nm”) This refers to column as an instance of Column class.“” (using double quotes) -> “col_nm” This refers to column as string type.There are several ways in which it can be done as shown below Different ways of creating delta table in Databricksįirst lets understand the syntax as to how to refer a Column.Spark Escape Double Quotes in Input File.

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