Tutorial on writing custom logic directly in Snowflake using SQL or JavaScript.

 

1. Introduction

Snowflake provides the ability to extend its functionality by writing custom logic using:

• SQL-based User-Defined Functions (UDFs) for reusable computations.
• JavaScript-based UDFs and Stored Procedures for more complex business logic.

2. Creating SQL-Based User-Defined Functions (UDFs)

SQL-based UDFs are useful when you want to perform custom calculations within SQL queries.

Example: Creating a SQL UDF

sql

CREATE OR REPLACE FUNCTION calculate_tax(price FLOAT, tax_rate FLOAT)
RETURNS FLOAT
AS
$$
  price * tax_rate
$$;

Usage:

sql

SELECT calculate_tax(100, 0.1); -- Returns 10.0

3. Creating JavaScript-Based User-Defined Functions (UDFs)

JavaScript UDFs allow you to implement more complex logic and handle conditional operations.

Example: Creating a JavaScript UDF

sql

CREATE OR REPLACE FUNCTION convert_case(input_string STRING)
RETURNS STRING
LANGUAGE JAVASCRIPT
AS
$$
  return input_string.toUpperCase();
$$;

Usage:

sql

SELECT convert_case('snowflake'); -- Returns 'SNOWFLAKE

4. Writing Stored Procedures in JavaScript

Stored procedures in Snowflake allow more advanced logic such as loops, conditional checks, and interactions with Snowflake objects.

Example: Creating a JavaScript Stored Procedure

sql

CREATE OR REPLACE PROCEDURE log_execution(message STRING)
RETURNS STRING
LANGUAGE JAVASCRIPT
AS
$$
  var result = "Log entry: " + message;
  return result;
$$;

Usage:

sql

CALL log_execution('Data pipeline executed successfully');

5. Using JavaScript to Execute SQL in Stored Procedures

Stored procedures in JavaScript can execute SQL statements dynamically.

Example: Dynamic Table Creation

sql

CREATE OR REPLACE PROCEDURE create_dynamic_table(table_name STRING)
RETURNS STRING
LANGUAGE JAVASCRIPT
AS
$$
  var sql_command = "CREATE TABLE IF NOT EXISTS " + table_name + " (id INT, name STRING)";
  snowflake.execute({ sqlText: sql_command });
  return "Table created: " + table_name;
$$;

Usage:

sql

CALL create_dynamic_table('employees');

6. Error Handling in JavaScript Stored Procedures

You can handle errors gracefully in JavaScript using try-catch blocks.

Example: Error Handling in Stored Procedures

sql

CREATE OR REPLACE PROCEDURE safe_insert(id INT, name STRING)
RETURNS STRING
LANGUAGE JAVASCRIPT
AS
$$
try {
    var sql_command = `INSERT INTO employees VALUES (${id}, '${name}')`;
    snowflake.execute({ sqlText: sql_command });
    return "Insert successful";
} catch (err) {
    return "Error: " + err.message;
}
$$;

Usage:

sql

CALL safe_insert(1, 'Alice');

7. Conclusion

• SQL UDFs are best for simple calculations.
• JavaScript UDFs provide flexibility for string manipulations and complex calculations.
• Stored Procedures enable dynamic SQL execution and complex workflows.

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