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Learn how to efficiently delete and reload data in Snowflake using tasks by implementing JavaScript stored procedures for seamless operations.
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This video is based on the question https://stackoverflow.com/q/67629956/ asked by the user 'danD' ( https://stackoverflow.com/u/11366870/ ) and on the answer https://stackoverflow.com/a/67631201/ provided by the user 'akshindesnowflake' ( https://stackoverflow.com/u/15088964/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Delete and Reload Data in Snowflake Tasks Effectively

Managing data in Snowflake often requires precise operations like deleting outdated data and reloading fresh information into your tables. This task can seem straightforward, but sometimes Snowflake's capabilities can present unique challenges.

In this guide, we will address the problem of executing deletion and insertion operations in the same task in Snowflake. If you’ve encountered any issues with this, rest assured—we’ll outline a clear solution using JavaScript stored procedures.

The Scenario

Imagine you have two tables: t2_load and t2_insert. The t2_load table is updated by Snowpipe, while t2_insert needs to be refreshed with the latest values from t2_load systematically. You attempted to create a task in Snowflake that deletes the contents of t2_insert and reloads it with records from a stream associated with t2_load.

Here’s what your original task looked like:

[[See Video to Reveal this Text or Code Snippet]]

While this task may look correct at first glance, it doesn’t actually work as expected because handling multiple SQL statements within a task's SQL execution context is not supported.

The Solution

To effectively delete and reload data in the same task, you can use a JavaScript stored procedure. This allows you to bundle multiple SQL commands, such as DELETE and INSERT, into a single executable unit.

Step-by-Step Guide

Create a JavaScript Stored Procedure: This procedure will handle your operations:

[[See Video to Reveal this Text or Code Snippet]]

Modify Your Task: Instead of executing multiple statements in your task, now you'll call this stored procedure:

[[See Video to Reveal this Text or Code Snippet]]

Test Your Task: After creating the task, make sure to test it to ensure it works as intended. Check if the t2_insert table reflects the changes after the task runs.

Why Use a Stored Procedure?

Flexibility: JavaScript stored procedures allow you to execute multiple SQL commands in a single unit.

Error Handling: You can implement error handling to gracefully manage exceptions during execution.

Modularity: By separating logic into procedures, you keep your code clean and maintainable.

Conclusion

Deleting and reloading data in Snowflake tasks can be accomplished efficiently by using JavaScript stored procedures. Following the steps outlined above equips you with a robust solution for managing dynamic data loads in your warehouse.

With this knowledge, you can streamline your data management processes and ensure that your tables are always up-to-date with the latest information from Snowpipe.

If you have further questions or need additional guidance, feel free to leave a comment below!