Database Management Systems
In MySQL, the JSON_KEYS() function returns keys from the top level value of a JSON object. The keys are returned as a JSON array, or, if a path argument is given, the top-level keys from the selected path.
You provide the JSON document as an argument to the function.
You can also (optionally) provide a second argument to specify where the “top-level” path starts from within the JSON document.
In MySQL, the JSON_EXTRACT() function returns data from a JSON document. The actual data returned is determined by the path you provide as an argument.
You provide the JSON document as the first argument, followed by the path of the data to return. You can also provide multiple paths to return data from multiple places in the document.
In MySQL, the JSON_CONTAINS_PATH() function tests whether or not a specified path is found in the given JSON document.
If the path is found, JSON_CONTAINS_PATH() returns 1, otherwise it returns 0.
In MySQL, the JSON_CONTAINS() function tests whether or not a specified value is found in the given JSON document or, optionally, at the specified path within the document.
If the value is found, JSON_CONTAINS() returns 1, otherwise it returns 0.
When using MySQL, you can use the JSON_VALID() function to test whether or not a string expression contains valid JSON.
If the expression contains valid JSON, JSON_VALID() returns 1, otherwise it returns 0.
In MySQL, the JSON_UNQUOTE() function “unquotes” a JSON document and returns the result as a utf8mb4 string.
You provide the JSON document as an argument, and the function will do the rest.
In MySQL, there are a number of functions to help you work with JSON documents. These include the JSON_SET(), JSON_INSERT(), and JSON_REPLACE() functions.
These three functions are related, yet they do differ slightly.
In MySQL, the JSON_SET() function inserts or updates values in a JSON document and returns the result.
You provide the JSON document as the first argument, followed by the path to insert into, followed by the value to insert. You can provide multiple path/value pairs if you need to update multiple values.
In MySQL, the JSON_REPLACE() function replaces values in a JSON document and returns the result.
You provide the JSON document as the first argument, followed by the path to replace data at, followed with the value to replace the existing value with.
You can replace data at multiple places in the document if required. To do this, simply provide multiple path/value pairs as required.
In MySQL, the JSON_REMOVE() function removes data from a JSON document and returns the result.
You provide the JSON document as the first argument, followed by the path to remove data from. You can provide multiple paths if required.