Скачать или смотреть Extracting JSON Data in BigQuery: A Guide to JSON_EXTRACT_SCALAR

Discover how to easily extract specific values from nested JSON data in BigQuery using `JSON_EXTRACT_SCALAR`. Learn step-by-step methods to retrieve data efficiently!
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Extracting JSON Data in BigQuery: A Guide to JSON_EXTRACT_SCALAR

When working with nested JSON data in Google BigQuery, you might encounter the need to extract specific values from complex structures. This guide focuses on answering the common question: How can I extract the default_value for the key "expiry_date" from a nested JSON object? Let’s break down the process step by step and see how you can achieve this efficiently using BigQuery's SQL features.

Understanding the JSON Structure

Before diving into the SQL queries, let’s take a look at the sample JSON structure we will be working with:

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

In this example, we have a JSON array containing objects, each with multiple attributes. Our goal is to extract the value of default_value associated with the key expiry_date, which is "2029-12-15".

Solution: Using BigQuery SQL

To extract the desired value from our JSON data, we can utilize BigQuery's JSON_EXTRACT_SCALAR function. Here are the steps you need to follow:

Step 1: Basic Extraction Query

You can use the following SQL query to successfully retrieve the default_value for expiry_date:

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

This query does the following:

SELECT JSON_EXTRACT_SCALAR: Extracts the default_value from the JSON objects.

FROM and UNNEST: Work together to flatten the JSON array into separate rows.

WHERE: Filters the results to find only the object where the key is 'expiry_date'.

Step 2: Testing with Sample Data

You can test the above SQL using sample data as shown below:

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

This query will output:

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

Step 3: Variations for Different Use Cases

Depending on your specific needs and real use cases, here’s an alternative approach that provides more context with additional columns:

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

This query includes all data from your dataset along with the extracted default_value, offering a broader context.

Conclusion

By utilizing the JSON_EXTRACT_SCALAR function in BigQuery, you can effortlessly extract specific pieces of data from nested JSON structures. Whether you need just the value of expiry_date or more contextual information alongside, these queries provide optimal solutions for handling JSON data in BigQuery.

Now that you have these examples and explanations, feel free to use them in your own projects and simplify your JSON data extraction process!