Extracto JSON
+----+--------+-------+-------+---------------------------------+
| id | name | price | stock | attr |
+----+--------+-------+-------+---------------------------------+
| 2 | Shirt | 10.50 | 78 | {"size": 42, "colour": "white"} |
| 3 | Blouse | 17.00 | 15 | {"colour": "white"} |
+----+--------+-------+-------+---------------------------------+
SELECT name FROM clothes WHERE JSON_EXTRACT(attr, '$.size') = 42;
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