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JSON_MODIFY (Transact-SQL)

  • Άρθρο

Applies to: SQL Server 2016 (13.x) and later Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics SQL analytics endpoint in Microsoft Fabric Warehouse in Microsoft Fabric

Updates the value of a property in a JSON string and returns the updated JSON string.

Transact-SQL syntax conventions

Syntax

JSON_MODIFY ( expression , path , newValue )

Arguments

expression

An expression. Typically the name of a variable or a column that contains JSON text.

JSON_MODIFY returns an error if expression doesn't contain valid JSON.

path

A JSON path expression that specifies the property to update.

path has the following syntax:

[append] [ lax | strict ] $.<json path>

  • append

    Optional modifier that specifies that the new value should be appended to the array referenced by <json path>.

  • lax

    Specifies that the property referenced by <json path> doesn't have to exist. If the property isn't present, JSON_MODIFY tries to insert the new value on the specified path. Insertion can fail if the property can't be inserted on the path. If you don't specify lax or strict, lax is the default mode.

  • strict

    Specifies that the property referenced by <json path> must be in the JSON expression. If the property isn't present, JSON_MODIFY returns an error.

  • <json path>

    Specifies the path for the property to update. For more info, see JSON Path Expressions (SQL Server).

    In SQL Server 2017 (14.x) and in Azure SQL Database, you can provide a variable as the value of path.

    JSON_MODIFY returns an error if the format of path isn't valid.

newValue

The new value for the property specified by path.

The new value must be varchar, nvarchar, or text.

In lax mode, JSON_MODIFY deletes the specified key if the new value is NULL.

JSON_MODIFY escapes all special characters in the new value if the type of the value is varchar or nvarchar. A text value isn't escaped if it's properly formatted JSON produced by FOR JSON, JSON_QUERY, or JSON_MODIFY.

Return value

Returns the updated value of expression as properly formatted JSON text.

Remarks

The JSON_MODIFY function lets you either update the value of an existing property, insert a new key:value pair, or delete a key based on a combination of modes and provided values.

The following table compares the behavior of JSON_MODIFY in lax mode and in strict mode. For more info about the optional path mode specification (lax or strict), see JSON Path Expressions (SQL Server).

New value Path exists Lax mode Strict mode
NOT NULL Yes Update the existing value. Update the existing value.
NOT NULL No Try to create a new key-value pair on the specified path.

This might fail. For example, if you specify the path $.user.setting.theme, JSON_MODIFY doesn't insert the key theme if the $.user or $.user.settings objects don't exist, or if settings is an array or a scalar value.		 Error - INVALID_PROPERTY
NULL Yes Delete the existing property. Set the existing value to null.
NULL No No action. The first argument is returned as the result. Error - INVALID_PROPERTY

In lax mode, JSON_MODIFY tries to create a new key:value pair, but in some cases it might fail.

JSON functions work the same whether the JSON document is stored in varchar, nvarchar, or the native json data type.

Examples

A. Basic operations

The following example shows basic operations that can be done with JSON text.

DECLARE @info NVARCHAR(100) = '{"name":"John","skills":["C#","SQL"]}';
PRINT @info;

-- Update name
SET @info = JSON_MODIFY(@info, '$.name', 'Mike');
PRINT @info;

-- Insert surname
SET @info = JSON_MODIFY(@info, '$.surname', 'Smith');
PRINT @info;

-- Set name NULL
SET @info = JSON_MODIFY(@info, 'strict $.name', NULL);
PRINT @info;

-- Delete name
SET @info = JSON_MODIFY(@info, '$.name', NULL);
PRINT @info;

-- Add skill
SET @info = JSON_MODIFY(@info, 'append $.skills', 'Azure');
PRINT @info;

Here's the result set.

{
    "name": "John",
    "skills": ["C#", "SQL"]
} {
    "name": "Mike",
    "skills": ["C#", "SQL"]
} {
    "name": "Mike",
    "skills": ["C#", "SQL"],
    "surname": "Smith"
} {
    "skills": ["C#", "SQL"],
    "surname": "Smith"
} {
    "skills": ["C#", "SQL", "Azure"],
    "surname": "Smith"
}

B. Multiple updates

With JSON_MODIFY, you can update only one property. If you have to do multiple updates, you can use multiple JSON_MODIFY calls.

DECLARE @info NVARCHAR(100) = '{"name":"John","skills":["C#","SQL"]}';
PRINT @info;

-- Multiple updates
SET @info = JSON_MODIFY(JSON_MODIFY(JSON_MODIFY(@info, '$.name', 'Mike'), '$.surname', 'Smith'), 'append $.skills', 'Azure');
PRINT @info;

Here's the result set.

{
    "name": "John",
    "skills": ["C#", "SQL"]
} {
    "name": "Mike",
    "skills": ["C#", "SQL", "Azure"],
    "surname": "Smith"
}

C. Rename a key

The following example shows how to rename a property in JSON text with the JSON_MODIFY function. First you can take the value of an existing property and insert it as a new key:value pair. Then you can delete the old key by setting the value of the old property to NULL.

DECLARE @product NVARCHAR(100) = '{"price":49.99}';
PRINT @product;

-- Rename property
SET @product = JSON_MODIFY(JSON_MODIFY(@product, '$.Price', CAST(JSON_VALUE(@product, '$.price') AS NUMERIC(4, 2))), '$.price', NULL);
PRINT @product;

Here's the result set.

{
    "price": 49.99
} {
    "Price": 49.99
}

If you don't cast the new value to a numeric type, JSON_MODIFY treats it as text and surrounds it with double quotes.

D. Increment a value

The following example shows how to increment the value of a property in JSON text with the JSON_MODIFY function. First you can take the value of the existing property and insert it as a new key:value pair. Then you can delete the old key by setting the value of the old property to NULL.

DECLARE @stats NVARCHAR(100) = '{"click_count": 173}';
PRINT @stats;

-- Increment value
SET @stats = JSON_MODIFY(@stats, '$.click_count', CAST(JSON_VALUE(@stats, '$.click_count') AS INT) + 1);
PRINT @stats;

Here's the result set.

{
    "click_count": 173
} {
    "click_count": 174
}

E. Modify a JSON object

JSON_MODIFY treats the newValue argument as plain text even if it contains properly formatted JSON text. As a result, the JSON output of the function is surrounded with double quotes and all special characters are escaped, as shown in the following example.

DECLARE @info NVARCHAR(100) = '{"name":"John","skills":["C#","SQL"]}';
PRINT @info;

-- Update skills array
SET @info = JSON_MODIFY(@info, '$.skills', '["C#","T-SQL","Azure"]');
PRINT @info;

Here's the result set.

{
    "name": "John",
    "skills": ["C#", "SQL"]
} {
    "name": "John",
    "skills": "[\"C#\",\"T-SQL\",\"Azure\"]"
}

To avoid automatic escaping, provide newValue by using the JSON_QUERY function. JSON_MODIFY knows that the value returned by JSON_QUERY is properly formatted JSON, so it doesn't escape the value.

DECLARE @info NVARCHAR(100) = '{"name":"John","skills":["C#","SQL"]}';
PRINT @info;

-- Update skills array
SET @info = JSON_MODIFY(@info, '$.skills', JSON_QUERY('["C#","T-SQL","Azure"]'));
PRINT @info;

Here's the result set.

{
    "name": "John",
    "skills": ["C#", "SQL"]
} {
    "name": "John",
    "skills": ["C#", "T-SQL", "Azure"]
}

F. Update a JSON column

The following example updates the value of a property in a table column that contains JSON.

UPDATE Employee
SET jsonCol = JSON_MODIFY(jsonCol, '$.info.address.town', 'London')
WHERE EmployeeID = 17;

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