How to Query Strength Value of a \'Knight\' from a Nested JSON Array in MySQL?

Querying a Nested JSON Array by Key

In MySQL, you can retrieve specific values from a nested JSON array using a combination of the JSON_TABLE() function and a WHERE clause.

Consider the following JSON array:

<code class="json">[
    {"Race": "Orc", "strength": 14},
    {"Race": "Knight", "strength": 7}
]</code>

To retrieve the strength of the Knight, you can use the following query:

<code class="sql">SELECT j.strength
FROM mytable,
JSON_TABLE(mycol, '$[*]' COLUMNS (
    race VARCHAR(10) PATH '$.Race',
    strength INT PATH '$.strength'
)) AS j
WHERE j.race = 'Knight'</code>

This query uses the JSON_TABLE() function to create a virtual table from the JSON array, with columns for each attribute. The WHERE clause is then used to filter the results based on the "Race" attribute.

Benefits and Limitations

Using JSON_TABLE() offers several benefits:

• Allows for selection and projection of specific attributes from the JSON document.
• Can be used to apply conditions to fields within the JSON data.

However, it also has some limitations:

• Requires specifying the attribute fields in the query, which may not be feasible if the data structure is unknown.
• Can result in complex queries when dealing with deeply nested or unstructured JSON documents.

Alternative Approach

If the data structure is unknown or changes frequently, an alternative approach is to use the JSON_SEARCH() function to find the path to the desired value, and then use the path operator to extract the value. However, this method does not allow for selection or projection as easily as JSON_TABLE().

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