joinOrNull
fun <T> Iterable<DataFrame<T>>.joinOrNull(joinType: JoinType = JoinType.Inner, selector: JoinColumnsSelector<T, T>? = null): DataFrame<T>?
Joins all DataFrames in this iterable into a single DataFrame.
Sequentially applies the join operation to each DataFrame in order. Returns null if the iterable is empty.
For more information: See join on the documentation website.
Return
resulting DataFrame, or null if the iterable is empty.
Parameters
joinType
JoinType defining how rows are matched and combined.
selector
optional JoinColumnsSelector specifying key columns.