Скачать или смотреть How to Call a Stored Procedure in Snowflake: Understanding Functions vs Procedures

Discover the difference between calling stored procedures and functions in Snowflake and learn how to correctly use them in your SQL queries.
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Understanding the Challenge of Calling Stored Procedures in Snowflake

If you're working with Snowflake and need to invoke a stored procedure within a SQL query, you might hit a roadblock. A common scenario arises when you try to call a stored procedure for multiple rows using a SELECT statement.

For example, you have a stored procedure named SP_CALC_BUCKET, which you can successfully call as follows:

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

This works well and returns the expected result. However, if you try to use it in a more extensive query like this:

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

You may encounter an error stating, "Unknown user-defined function SP_CALC_BUCKET."

So what's going wrong, and how can you resolve it?

The Solution: Using Functions Instead of Stored Procedures

The primary reason for this error is that Snowflake differentiates between stored procedures and functions. Here’s a breakdown of how these two components operate:

Stored Procedures vs. Functions

Stored Procedures:

Called as independent statements.

Do not return a value, which means they cannot be used in all contexts.

For example, you can call a stored procedure using:

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

Functions:

Can evaluate to a value and be used where general expressions are applicable.

Used in expressions, like in SELECT statements.

Example of calling a function:

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

What You Can Do

Create a User-Defined Function (UDF):

If you want to perform the same operation you’re attempting with your stored procedure, consider writing a user-defined function that mirrors what your stored procedure does.

Modify Your Query Context:

Replace the stored procedure call with your newly created UDF in your SELECT statement. This will ensure that Snowflake recognizes your function and is able to execute it over the rows you specify.

Wrap Up

To summarize, when working with stored procedures and SQL in Snowflake, it's crucial to remember that stored procedures can’t be directly used within expressions such as SELECT statements. Instead, by creating and using a function, you can achieve your desired outcomes without running into the "unknown user-defined function" error.

By understanding these distinctions and knowing how to create and utilize user-defined functions effectively, you'll enhance your SQL querying capabilities in Snowflake significantly.

If you encounter any other issues or have questions regarding SQL and Snowflake, feel free to reach out!