User-defined functions in Snowflake

Data Types and Functions in Snowflake

Jake Roach

Field Data Engineer

What are user-defined functions (UDFs)?

"Package" complex logic into a single, reusable function

Easier to read
Reduces chances for mistakes
Share logic with others

... let's take a closer look!

Image showing the idea of a user-defined function.

Refactoring code with a UDF

SELECT
    first_name, last_name, school_name,

    CONCAT(
        first_name,
        '.',
        last_name,
        '@',
        school_name,
        '.com'
    )

FROM STUDENTS.personal_info;

SELECT
    first_name, 
    last_name, 
    school_name,


    -- Reusable, easy to read
    build_email_address(
        first_name, 
        last_name, 
        school_name
    ) AS email_address


FROM STUDENTS.personal_info;

Defining a UDF

CREATE OR REPLACE FUNCTION <name> (

    -- Specify arguments and types
    <arg1> <type1>, 
    <arg2> <type2>, 
    ...
)


RETURN <type>  -- Declare return type


AS

$$
-- Define your function here
$$

CREATE OR REPLACE FUNCTION
Provide a function name
In parentheses, specify the name and type of each argument
Declare the RETURN type
Define your logic in $$ ... $$!

Building an email address

CREATE OR REPLACE FUNCTION build_email_address(

    first_name TEXT,
    last_name TEXT,
    school_name TEXT

)


RETURN TEXT


AS

$$
CONCAT(LOWER(first_name), '.', LOWER(last_name), '@', LOWER(school_name), '.com')
$$;

Using a UDF

SELECT
    first_name, last_name, school_name,
    build_email_address(first_name, last_name, school_name) AS email_address

FROM STUDENTS.personal_info;

      first_name  |  last_name  |  school_name  |        email_address
     ------------ | ----------- | ------------- | ----------------------------
       Ryan       |  Cohen      |  Harvard      |  [email protected]
       Tatiana    |  Doyle      |  Stanford     |  [email protected]
       Pankaj     |  Pandey     |  MIT          |  [email protected]
       Jake       |  Roach      |  Purdue       |  [email protected]

Let's practice!

Data Types and Functions in Snowflake