# Multiple DataFrames

> For the complete documentation index, see [llms.txt](https://kotlin.github.io/dataframe/llms.txt).

Operations that combine several [DataFrame](dataframe.html) objects into one.

API reference: [api package](https://kotlin.github.io/dataframe/api-docs/core/org.jetbrains.kotlinx.dataframe.api/index.html)

* [addAll](add.html#add-all-columns-from-another-dataframe) — union of columns from several [DataFrame](dataframe.html) objects

* [concat](concat.html) — union of rows from several [DataFrame](dataframe.html) objects

* [join](join.html) — sql-like join of two [DataFrame](dataframe.html) objects by key columns

* [joinWith](joinwith.html) — join of two [DataFrame](dataframe.html) objects by an expression that evaluates joined [DataRows](datarow.html) to Boolean