In MariaDB, JSON_LENGTH() is a built-in function that returns the length of a JSON document.
When you call this function, you provide the JSON document as an argument. You can also provide a path argument to return the length of a value within the document.
In MariaDB, JSON_KEYS() is a built-in function that returns an array of the top-level keys from a JSON document. If a path is provided, it returns the top-level keys from that path.
It excludes keys from nested sub-objects in the specified level.
Also, if the selected object is empty, an empty array is returned.
In MariaDB, JSON_SET() is a built-in function that updates or inserts data into a JSON document and returns the result.
JSON_SET() can update and insert data, whereas JSON_INSERT() can only insert data, and JSON_REPLACE() can only update data.
In MariaDB, JSON_REPLACE() is a built-in function that replaces existing values in a JSON document and returns the result.
In MariaDB, JSON_INSERT() is a built-in function that inserts data into a JSON document, and returns the result.
In MariaDB, JSON_DEPTH() is a built-in function that allows you to check the depth of a JSON document.
It accepts the JSON document as an argument, and returns the maximum depth of the document.
In MariaDB, JSON_EXISTS() is a built-in function that allows you to check whether a value exists at a specified path in the JSON document.
It accepts the JSON document as an argument, and returns 1 if the path is found, and 0 if it’s not.
The MariaDB documentation states that the function “determines whether a specified JSON value exists in the given data”. However, the function doesn’t actually appear to check for a given value. It’s probably more accurate to say that it determines whether a specified path exists, or that a value exists at the specified path.
For checking that the actual value exists, you can use the JSON_CONTAINS() function.
In MariaDB, JSON_QUERY() is a built-in function that returns an object or array from a JSON document, based on the path provided.
It’s similar to the JSON_VALUE() function, except that it returns an object or array instead of a scalar (JSON_VALUE() returns a scalar).
In MariaDB, JSON_VALUE() is a built-in function that returns a scalar value from a JSON document. More specifically, it returns the scalar specified by the path provided.
In MariaDB, JSON_MERGE_PATCH() is a built-in function that merges two or more JSON documents and returns the result.
The JSON_MERGE_PATCH() function is an RFC 7396-compliant replacement for the JSON_MERGE() function, which has been deprecated.