How To Guides
How to use union in Databricks?

How to use union in Databricks?

Learn how to effectively use the union operation in Databricks to combine datasets and perform advanced data manipulation.

Databricks is a powerful data analytics platform that offers a wide range of functionalities, including the ability to perform unions on datasets. In this article, we will explore how to effectively use the union operation in Databricks to combine and analyze data from multiple sources.

Understanding the Concept of Union in Databricks

The union operation in Databricks allows you to combine two or more datasets into a single dataset. The resulting dataset will contain all the rows from each input dataset without any duplicates. This is particularly useful when you have multiple datasets that share a similar structure and you want to consolidate the data for further analysis.

Definition of Union in Databricks

In Databricks, the union operation is a set operation that combines the rows of two or more datasets into a single dataset. It is similar to the UNION keyword in SQL and the UNION operation in other programming languages.

Importance of Union in Data Analysis

Union is an essential operation in data analysis as it allows you to aggregate and analyze data from multiple sources effectively. By combining datasets, you can gain a more comprehensive understanding of your data and uncover valuable insights that may not be apparent when analyzing individual datasets separately.

One of the key benefits of using the union operation in Databricks is the ability to handle datasets with overlapping data. When you have multiple datasets that contain similar information, such as customer data from different regions or time periods, you can use the union operation to merge them into a single dataset. This consolidation process eliminates the need for manual data merging and ensures that you have a complete and accurate representation of your data.

Furthermore, the union operation in Databricks is not limited to datasets of the same structure. You can combine datasets with different column names or data types, as long as the number and order of columns match. This flexibility allows you to integrate data from various sources, such as CSV files, databases, or streaming platforms, into a unified dataset for analysis.

Another advantage of using the union operation is the ability to perform data transformations and manipulations on the combined dataset. Once you have merged the datasets, you can apply filters, aggregations, or any other data manipulation techniques to derive meaningful insights. This flexibility empowers data analysts and scientists to explore and analyze complex datasets with ease.

Setting Up Your Databricks Environment

Before you can start using the union operation in Databricks, there are a few requirements and steps you need to follow to set up your environment.

Setting up your Databricks environment is an essential first step to harnessing the power of the union operation. By ensuring that you have the necessary access, permissions, and datasets in the right format, you can seamlessly perform data manipulations and unlock valuable insights.

Requirements for Using Union in Databricks

To use the union operation in Databricks, you need access to a Databricks workspace and the necessary permissions to create and manipulate datasets. This ensures that you have the freedom to explore and combine data from various sources, empowering you to make informed decisions based on comprehensive insights.

Furthermore, it is crucial to have the datasets you want to union stored in a format supported by Databricks. Whether your data is in CSV, Parquet, or JSON format, Databricks provides the flexibility to seamlessly integrate and analyze diverse data sources.

Steps to Set Up Databricks for Union

Once you meet the requirements, follow these steps to set up your Databricks environment for using the union operation:

  1. Create a Databricks workspace if you don't already have one.
  2. Setting up a cluster in Databricks is the next crucial step. By configuring a cluster, you ensure that you have the necessary computational resources to process your data efficiently. This empowers you to handle large datasets and perform complex data manipulations with ease.
  3. Upload the datasets you want to union to the Databricks File System (DBFS) or connect to external data sources. This step allows you to seamlessly access and integrate your data, ensuring that you have a comprehensive view for analysis and decision-making.
  4. Import the necessary libraries or packages for data manipulation. Databricks provides a rich ecosystem of libraries and packages that enable you to perform advanced data manipulations. By importing the relevant libraries, you can leverage powerful functions and methods to transform and combine your datasets effectively.

By following these steps, you can establish a robust foundation for utilizing the union operation in Databricks. With your environment set up, you are now ready to unleash the full potential of your data and extract meaningful insights that drive business success.

Detailed Guide on Using Union in Databricks

Once your Databricks environment is set up, you can start using the union operation to combine your datasets. This section provides a detailed guide on how to prepare your data, execute the union command, and troubleshoot common union errors.

Preparing Your Data for Union

Before you can perform a union, it's crucial to ensure that your datasets have a compatible structure. This means that the column names, data types, and order should match across the datasets. If needed, you can use data transformation operations to align the structure of the datasets before performing the union.

For example, let's say you have two datasets: dataset1 and dataset2. Dataset1 has columns "name", "age", and "gender", while dataset2 has columns "name", "age", and "city". To make the datasets compatible, you can add a new column "city" to dataset1 and populate it with null values.

Executing the Union Command

To perform a union in Databricks, you can use the union function or the unionByName function from the DataFrame or Dataset API. These functions allow you to specify the datasets you want to union and return a new dataset with the combined rows.

Here's an example of how to use the union function:

val unionData = dataset1.union(dataset2)

After executing this command, the unionData dataset will contain all the rows from dataset1 and dataset2.

Troubleshooting Common Union Errors

While using the union operation, you may encounter certain errors or challenges. Some common issues include incompatible data types, missing columns, or duplicate rows. It's important to carefully review your datasets and the union command to identify and resolve any potential errors.

One common error is when the data types of corresponding columns in the datasets are not compatible. For example, if dataset1 has a column "age" with data type Integer and dataset2 has a column "age" with data type String, the union operation will fail. To resolve this, you can either convert the data types to match or exclude the incompatible columns from the union.

Another challenge is when one of the datasets has missing columns. In this case, the union operation will fail as the column structure is not compatible. To fix this, you can add the missing columns to the dataset with null values or exclude the columns from the union if they are not required.

Duplicate rows can also cause issues during the union operation. If both datasets contain duplicate rows, the resulting dataset will have duplicate rows as well. To remove duplicate rows, you can use the distinct function after performing the union.

Optimizing Your Use of Union in Databricks

To get the most out of the union operation in Databricks, it's essential to follow best practices and avoid common pitfalls. This section provides valuable tips for optimizing your use of union and improving the efficiency of your data analysis workflows.

Best Practices for Using Union

When using the union operation, consider the following best practices:

  • Ensure that the datasets have compatible structures.
  • Perform any necessary data transformations before performing the union.
  • Avoid using union on large datasets that exceed the available memory capacity.
  • Review the performance implications of the union operation and optimize accordingly.

Avoiding Common Pitfalls in Using Union

During the union operation, it's important to be aware of common pitfalls that can affect your analysis. Some pitfalls to avoid include:

  • Assuming that the union operation will automatically remove duplicate rows.
  • Forgetting to align the column names and data types across datasets.
  • Not considering the performance impact of performing unions on large datasets.

Advanced Union Techniques in Databricks

In addition to the basic union functionality, Databricks offers advanced techniques for performing unions on large datasets and combining the union operation with other Databricks functions.

Using Union with Large Datasets

When dealing with large datasets, it's crucial to consider the memory and processing limitations of your Databricks environment. Databricks provides optimizations like predicate pushdown and column pruning to efficiently perform unions on large datasets and minimize the impact on performance.

Combining Union with Other Databricks Functions

Databricks provides a rich set of functions and libraries that you can combine with the union operation to enhance your data analysis. For example, you can use the join operation to combine datasets based on common keys before performing the union, or you can leverage advanced analytics libraries like Spark MLlib for machine learning tasks.

By leveraging these advanced union techniques, you can unlock the full potential of Databricks and perform complex data analysis tasks with ease.


In conclusion, the union operation in Databricks is a powerful tool for combining and analyzing data from multiple sources. By following the steps outlined in this article and adopting best practices, you can effectively utilize the union operation in Databricks to gain valuable insights and drive data-driven decision making. Remember to always consider the compatibility, preparation, and optimization aspects when working with unions in Databricks, and leverage advanced techniques to handle large datasets and combine unions with other functionalities. With the union operation in your toolkit, you can take your data analysis to the next level.

New Release

Get in Touch to Learn More

See Why Users Love CastorDoc
Fantastic tool for data discovery and documentation

“[I like] The easy to use interface and the speed of finding the relevant assets that you're looking for in your database. I also really enjoy the score given to each table, [which] lets you prioritize the results of your queries by how often certain data is used.” - Michal P., Head of Data