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Snowflake’s ARRAY_CAT Function

   January 9, 2024
Snowflake

One of its lesser-known but highly useful functions is ARRAY_CAT. This article provides a comprehensive guide to understanding and utilizing the ARRAY_CAT function in Snowflake, complete with real-world examples.

What is the ARRAY_CAT Function?

ARRAY_CAT is a function in Snowflake that concatenates two arrays to form a single array. It’s particularly useful in scenarios where data from different sources or categories needs to be combined into a single, unified array.

Benefits of Using ARRAY_CAT

  • Data Integration: Easily merge data from various arrays, simplifying data analysis.
  • Efficiency: Reduces the need for complex queries and multiple steps in data processing.
  • Flexibility: Works with arrays containing different data types.

Real-World Applications

ARRAY_CAT finds its applications in data transformation, reporting, and analytics where combining array data is essential. It’s particularly useful in sectors like finance, marketing, and sales where data consolidation is a frequent requirement.

Prerequisites

Before diving into the ARRAY_CAT function, ensure you have a basic understanding of Snowflake and SQL. Familiarity with array data types in SQL will be beneficial.

Example Scenario and Implementation

Let’s consider a scenario where we have a table freshers_employees in Snowflake, which records the departments associated with each employee. The goal is to concatenate the department arrays of each employee.

CREATE TABLE freshers_employees (
  employee_id INT,
  department VARCHAR(50)
);

INSERT INTO freshers_employees (employee_id, department)
VALUES
  (1, 'Sales'),
  (2, 'Marketing'),
  (3, 'Sales'),
  (4, 'HR'),
  (5, 'Marketing'),
  (1, 'BusinessDevelopment'),
  (2, 'Advertisement'),
  (3, 'BusinessDevelopment');

Using ARRAY_CAT

To use ARRAY_CAT, we first need to aggregate the departments per employee into arrays. Then, ARRAY_CAT can be applied to concatenate these arrays.

-- Aggregate departments per employee
SELECT employee_id, ARRAY_AGG(department) AS departments
FROM freshers_employees
GROUP BY employee_id;

This query provides an array of departments per employee. To concatenate arrays, use:

-- Example of ARRAY_CAT usage
SELECT ARRAY_CAT(departments, ARRAY['NewDepartment']) 
FROM (SELECT employee_id, ARRAY_AGG(department) AS departments
      FROM freshers_employees
      GROUP BY employee_id);

Result

EMPLOYEE_ID	DEPARTMENTS
3	[  "Sales",  "BusinessDevelopment"]
1	[  "Sales",  "BusinessDevelopment"]
4	[  "HR"]
5	[  "Marketing"]
2	[  "Marketing",  "Advetisment"]

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