the-biergarten-app/archive/sql-stored-procs-functions/02-functions/UDF_GetStateProvinceIdByCode.sql

CREATE OR ALTER FUNCTION dbo.UDF_GetStateProvinceIdByCode(
    @StateProvinceCode NVARCHAR(6)
)
    RETURNS UNIQUEIDENTIFIER
AS
BEGIN
    DECLARE
        @StateProvinceId UNIQUEIDENTIFIER;
    SELECT @StateProvinceId = StateProvinceID
    FROM dbo.StateProvince
    WHERE ISO3166_2 = @StateProvinceCode;
    RETURN @StateProvinceId;
END;