How to use external table in Snowflake?

In this article, we will explore the concept of using external tables in Snowflake and learn how to effectively utilize them in your Snowflake environment. Understanding the functionality and benefits of external tables is crucial for maximizing the power of Snowflake's cloud data platform.

Understanding External Tables in Snowflake

Definition and Function of External Tables

An external table is a virtual table in Snowflake that allows you to reference data files stored outside the Snowflake database. These data files can be located in cloud storage services such as Amazon S3, Microsoft Azure Blob Storage, or Google Cloud Storage. External tables provide a seamless way to integrate external data sources into your Snowflake environment without the need to load the data into Snowflake's storage.

External tables act as a metadata layer, allowing you to query and join the external data as if it were stored within Snowflake. This flexibility enables you to leverage the power of Snowflake's query engine to analyze and derive insights from a wide variety of data sources, including structured, semi-structured, and unstructured data.

Benefits of Using External Tables

There are several benefits to using external tables in Snowflake:

1. Cost Savings: By storing your data in cloud storage services and using external tables, you can reduce storage costs as Snowflake charges only for the compute resources used during query execution.  
2. Flexibility: External tables allow you to seamlessly integrate data from multiple sources into your Snowflake environment, enabling holistic data analysis and insights.  
3. Performance: With external tables, you can leverage Snowflake's parallel processing capabilities to efficiently query and analyze large datasets stored externally.  

One of the key advantages of using external tables in Snowflake is the cost savings it offers. By storing your data in cloud storage services such as Amazon S3, Microsoft Azure Blob Storage, or Google Cloud Storage, you can significantly reduce your storage costs. Snowflake charges only for the compute resources used during query execution, which means you don't have to pay for the storage of your data within Snowflake's storage. This cost-effective approach allows you to scale your data storage without incurring additional expenses.

Another benefit of using external tables is the flexibility it provides. With external tables, you can seamlessly integrate data from multiple sources into your Snowflake environment. Whether your data is structured, semi-structured, or unstructured, Snowflake's query engine can handle it all. This means you can perform holistic data analysis and gain valuable insights by combining data from different sources. You can easily join external tables with tables stored within Snowflake, enabling you to create comprehensive and meaningful reports.

Performance is also a major advantage of using external tables in Snowflake. Snowflake's parallel processing capabilities allow you to efficiently query and analyze large datasets stored externally. By leveraging the power of distributed computing, Snowflake can process queries in parallel across multiple compute resources. This results in faster query execution times and improved performance, even when dealing with massive amounts of data.

In conclusion, external tables in Snowflake offer numerous benefits, including cost savings, flexibility, and improved performance. By leveraging external tables, you can seamlessly integrate data from various sources into your Snowflake environment and analyze it using Snowflake's powerful query engine. This enables you to derive valuable insights and make data-driven decisions with ease.

Setting Up Your Snowflake Environment

Welcome to the world of Snowflake! In order to start using external tables in Snowflake, there are a few prerequisites that you need to take care of. Let's dive into the necessary tools and requirements.

Necessary Tools and Requirements

Before you can start using external tables in Snowflake, there are a few prerequisites:

• A Snowflake account: You need access to a Snowflake account to create and manage external tables. Snowflake provides a secure and scalable cloud data platform that allows you to store, analyze, and share your data effortlessly.
• Cloud storage service account: You must have an account with a supported cloud storage service (Amazon S3, Microsoft Azure Blob Storage, or Google Cloud Storage). Snowflake seamlessly integrates with these cloud storage services, allowing you to leverage the power and flexibility of cloud computing.

Steps to Configure Your Snowflake Environment

Now that you have the necessary tools and requirements in place, let's move on to configuring your Snowflake environment for using external tables. Follow these steps:

1. Create a stage: A stage is a logical container in Snowflake that points to your cloud storage account. It acts as a bridge between Snowflake and your external data files. To create a stage, you need to provide the necessary information about your cloud storage account, such as the storage provider, bucket, and credentials. This will allow Snowflake to access your external data files with ease.
2. Grant necessary privileges: In order to interact with the external tables, you need to grant the necessary privileges to the Snowflake user or role. Privileges control the level of access and actions that a user or role can perform on the external tables. By granting the appropriate privileges, you ensure that only authorized users can interact with the external tables and maintain data security.
3. Set up file formats: File formats define the structure and properties of your external data files. When setting up file formats, you specify options such as field delimiter, compression type, character encoding, and more. This step is crucial as it ensures that Snowflake can correctly interpret and process your external data files, regardless of their format or encoding.
4. Create external tables: Finally, it's time to create the external tables! External tables are virtual tables that reference the data files stored in your cloud storage account. When creating an external table, you provide the necessary details such as the file format, location, and any additional parameters required. This allows Snowflake to seamlessly integrate the external data into your Snowflake environment, making it available for querying and analysis.

By following these steps, you will successfully configure your Snowflake environment for using external tables. Now, you can leverage the power of Snowflake's cloud data platform and seamlessly analyze your external data with ease. Happy querying!

Creating an External Table in Snowflake

Understanding the Syntax

To create an external table in Snowflake, you need to use the CREATE EXTERNAL TABLE statement. The syntax is as follows:

CREATE EXTERNAL TABLE (  ,   ,  ...)LOCATION = ''FILE_FORMAT = ();

Replace , , , , and  with the appropriate values for your use case.

Important Parameters and Their Uses

When creating an external table, you can specify optional parameters to tailor the behavior of the table. Some important parameters and their uses include:

• AUTO_REFRESH: Specifies whether to automatically update the metadata of the external table when changes occur in the underlying data files.  
• COMPRESSION: Defines the compression type used for the data files. Snowflake supports various compression algorithms such as GZIP, ZSTD, and SNAPPY.  
• SAMPLE_PCT: Determines the percentage of data to sample when collecting metadata statistics for the external table.  

Loading Data into External Tables

Preparing Your Data for Loading

Prior to loading data into your external tables, ensure that your data files in the cloud storage are properly formatted and compatible with the specified file format. Verify that the data files conform to the expected schema and data types.

If required, you can perform preprocessing tasks such as data cleansing or transformation before loading the data into the external tables.

Executing the Load Operation

To load data into your external tables, use the COPY INTO statement in Snowflake. The syntax is as follows:

COPY INTO  FROM ''FILE_FORMAT = ();

Replace , , and  as per your requirement.

The COPY INTO statement instructs Snowflake to load data from the specified data files located in the cloud storage into the external table. Snowflake automatically parallelizes the load operation, leveraging the power of its distributed architecture.

Querying Data from External Tables

Basic Querying Techniques

Querying data from external tables in Snowflake is similar to querying regular tables. You can use SQL statements to retrieve, manipulate, and analyze the data stored in the external tables.

For example:

SELECT * FROM WHERE ;

Replace  and  with your specific values.

Advanced Querying Techniques

Snowflake provides advanced querying capabilities that can be applied to external tables as well. You can perform joins, aggregations, window functions, and other complex operations on data stored in external tables.

It's worth noting that Snowflake automatically optimizes queries on external tables by pushing down filters and aggregations to the cloud storage layer, leading to efficient query execution.

By harnessing the full power of Snowflake's SQL and analytical capabilities, you can gain valuable insights from the data stored in your external tables.

Conclusion

In conclusion, external tables in Snowflake provide a powerful mechanism for integrating and analyzing data from external sources. By understanding the concept, benefits, and practical techniques for working with external tables, you can unlock the full potential of Snowflake's cloud data platform.

Start leveraging external tables in Snowflake today to seamlessly integrate diverse data sources and drive actionable insights for your business.