How to Convert JSON to Array of Strings in SQL

Discover effective techniques to `convert JSON data into a properly formatted array of strings` using SQL. Follow our detailed guide for easy implementation.
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How to Convert JSON to Array of Strings in SQL

In today's data-driven environment, being able to manipulate and present data efficiently is a valuable skill. One common task is converting data formatted as JSON into a more usable structure, such as an array of strings. This guide will guide you through the process of converting a simple SQL table column into a JSON-formatted array, step by step.

Understanding the Problem

Imagine you have a SQL table with a column named Col1 that contains string values:

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Your goal is to format this data into JSON like this:

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However, if you simply use the FOR JSON PATH method, you might get an incorrect format like this instead:

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This happens because the default behavior of FOR JSON PATH doesn't create a proper array format. Let’s explore how to achieve the desired json array formatting using SQL.

The Solution

Using String Aggregation

If you are using SQL Server 2017 or later, the easiest way to convert your column to a JSON array is by using the STRING_AGG() function. Here’s the SQL code you would use:

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Breakdown of the Code

STRING_AGG(): This function aggregates the values in Col1 into a single string, separated by commas and formatted with quotes.

STRING_ESCAPE(): This function ensures that any special characters in the string are escaped appropriately, preserving your JSON format integrity.

JSON_QUERY(): Wrapping the aggregated string in JSON_QUERY() converts it to a valid JSON array format.

Expected Results

Running the above SQL code will give you the following output:

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Alternative Approach for Older SQL Versions

If your SQL Server version is older than 2017, you won’t have access to the STRING_AGG() function. Instead, you can utilize the STUFF() function in combination with FOR XML PATH. Here’s how you can do it:

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Explanation of the Alternative Code

STUFF(): This function is used to manipulate strings, in this case, removing the initial unwanted characters from the concatenated strings.

FOR XML PATH: Used in this method to concatenate values from Col1 into one string while retaining the proper escape sequences.

Conclusion

Transforming SQL data into JSON format is a common yet essential skill in data manipulation. By using STRING_AGG() for newer versions of SQL Server or falling back to STUFF() with FOR XML in older versions, you can effectively convert a SQL column into a well-structured JSON array. This not only helps in presentation but also enhances data usability in applications that consume JSON outputs.

Now you have the tools to efficiently convert JSON to an array of strings and ensure your data is formatted to meet your needs. Happy coding!