How to Aggregate the Sum of an Array in BigQuery SQL

Learn how to aggregate and sum an array contained in a field using BigQuery SQL with clear steps and examples.
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How to Aggregate the Sum of an Array in BigQuery SQL

If you are working with Google BigQuery and are confronted with the need to sum values from an array of numbers contained in a field, you might find the process a bit daunting. This common scenario, especially in data analytics, requires a specific approach to ensure that you can easily manipulate and aggregate your data to extract meaningful insights.

In this guide, we will walk you through how to aggregate the sum of an array in a SQL query using BigQuery. We'll explain the problem, break down the logic needed for the solution, and provide clear code examples to facilitate your understanding. Let’s dive in!

Understanding the Problem

Suppose you have a table with a single field that contains numerous arrays of numeric values. For instance, here is a simplified representation of such a table:

Field[5640.0, 11252.0, 16836.0, ...][6789.0, 13543.0, 20264.0, ...][7409.0, 14781.0, 22115.0, ...]Your goal is to sum all the numbers in each array stored within this field. You might be unsure whether to use UNNEST, and if so, how to implement it correctly. Let’s clarify this.

The Solution Step-by-Step

To effectively aggregate the sum of numbers in an array within a BigQuery SQL query, we can follow these structured steps:

Step 1: Define the Arrays

First, you will need to initialize a WITH clause to define the structure of your arrays. As per the example provided, you can represent your field in a subquery as follows:

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

Step 2: Summing the Values

Next, you will proceed to sum the values contained in each array. The UNNEST function is particularly useful here, as it allows you to expand the array into separate rows. Here's how you can accomplish this:

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

Putting It All Together

Here’s the complete SQL query that combines both steps effectively. This query will produce the sum for each array in your defined table.

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

Expected Output

When you run the above query, you will receive an output that lists each array alongside its corresponding sum. It would look something like this:

Fieldsums[5640.0, 11252.0, ...]157,676.0[6789.0, 13543.0, ...]164,575.0[7409.0, 14781.0, ...]188,880.0Conclusion

Aggregating the sums of arrays within fields in BigQuery SQL can be efficiently performed using the UNNEST function within a subquery. By following the structured steps outlined in this guide, you should now be equipped to handle similar queries in your own data analytics projects.

Happy querying!