Extracting Exact Numbers from JSON Strings in SQL Server

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In this article, we will explore how to extract exact numbers from JSON strings in Microsoft SQL Server. The process involves using string methods and functions to isolate the desired values within a complex data structure.

Introduction to SQL Server’s JSON Support

SQL Server 2016 and later versions introduced native support for JSON data type. This feature allows us to store, manipulate, and query JSON data as if it were a table in our database.

However, when dealing with older versions of SQL Server (prior to 2016), we have to rely on string methods and functions to extract values from JSON strings.

The Problem: Extracting Numbers from JSON Strings

The question at hand is how to extract the exact numbers 189 and 190 from a JSON string in the format:

{"OWLSObjKey":{"key":"OWLSObjKey","value":"189","type":null},"OWLSObjType":{"key":"OWLSObjType","value":"17","type":null},"ObjKey":{"key":"ObjKey","value":"189","type":null},"ObjType":{"key":"ObjType","value":"17","type":null}}
{"OWLSObjKey":{"key":"OWLSObjKey","value":"190","type":null},"OWLSObjType":{"key":"OWLSObjType","value":"17","type":null},"ObjKey":{"key":"ObjKey","value":"190","type":null},"ObjType":{"key":"ObjType","value":"17","type":null}}

Solution: Using String Methods and Functions

One approach to solving this problem is by using string methods and functions available in SQL Server. The idea is to use the STUFF() function to remove unwanted characters from the JSON string, leaving us with the desired value.

Step 1: Creating a Sample Table and Inserting Data

We start by creating a sample table and inserting data into it:

-- Create a sample table
declare @table table (trigparams nvarchar(2000))

-- Insert data into the table
insert into @table 
values
('{"OWLSObjKey":{"key":"OWLSObjKey","value":"189","type":null},"OWLSObjType":{"key":"OWLSObjType","value":"17","type":null},"ObjKey":{"key":"ObjKey","value":"189","type":null},"ObjType":{"key":"ObjType","value":"17","type":null}}'),
('{"OWLSObjKey":{"key":"OWLSObjKey","value":"190","type":null},"OWLSObjType":{"key":"OWLSObjType","value":"17","type":null},"ObjKey":{"key":"ObjKey","value":"190","type":null},"ObjType":{"key":"ObjType","value":"17","type":null}}')

Step 2: Querying the Data and Extracting the Numbers

We then use a query to extract the numbers from the trigparams column:

-- Use CROSS APPLY to apply a function to each row in the table
SELECT LEFT(CutOff,CHARINDEX('"',CutOff)-1)
FROM @table t
CROSS APPLY (
    SELECT STUFF(t.trigparams,1,CHARINDEX('"value":"',t.trigparams)+8,'') AS CutOff
) A;

Explanation of the Query

Let’s break down the query:

SELECT LEFT(CutOff,CHARINDEX('"',CutOff)-1) : This line uses the LEFT() function to extract the first characters up to the occurrence of a double quote ("). We subtract 1 from the index because CHARINDEX() returns the position of the character after it.
FROM @table t : This line specifies the table we want to query, which is @table.
CROSS APPLY (...) A(CutOff) : This line applies a subquery (the one that uses STUFF()) to each row in the table. The result is a new column called CutOff.

Explanation of the STUFF Function

The STUFF() function removes characters from a specified position to a specified number of positions.

STUFF(t.trigparams, 1, CHARINDEX('"value":"', t.trigparams) + 8) : This line uses STUFF() to remove the unwanted characters (the string "value":) starting at position 1 and ending at position CHARINDEX('"value":"', t.trigparams) + 8. The result is a new string that starts from the first occurrence of a double quote (") followed by a space.

Conclusion

In this article, we explored how to extract exact numbers from JSON strings in Microsoft SQL Server. We used string methods and functions like STUFF() to isolate the desired values within a complex data structure.

By understanding how these functions work, you can effectively handle similar problems when working with JSON data in your database.

Additional Considerations

When working with large datasets or performance-critical applications, consider using indexing strategies and efficient data types (like nvarchar(2000) for the trigparams column) to optimize query performance.
Be mindful of the character encoding when dealing with internationalized strings. For example, some characters may require more bytes than others due to differences in Unicode encoding schemes.

I hope this detailed explanation helped you understand how to extract numbers from a JSON string using SQL Server’s built-in functions and methods!

Last modified on 2024-01-06