Looked through the docs, but didn't find an explanation of what exact purpose the $ is doing in the following lines of code:

Some code I found in our codebase:

set jsonData = JSON_ARRAY_APPEND(coalesce(jsonData, '[]'), '$',
                                 JSON_OBJECT('name', 'facility_id', 'old_value', '', 'new_value', NEW.facility_id));

and some code found in MySql docs:

mysql> SELECT JSON_ARRAY_APPEND(@j, '$[1]', 1);

Looked through the docs, but didn't find an explanation of what exact purpose the $ is doing in the following lines of code:

Some code I found in our codebase:

set jsonData = JSON_ARRAY_APPEND(coalesce(jsonData, '[]'), '$',
                                 JSON_OBJECT('name', 'facility_id', 'old_value', '', 'new_value', NEW.facility_id));

and some code found in MySql docs:

mysql> SELECT JSON_ARRAY_APPEND(@j, '$[1]', 1);

• sql
• mysql
• database

• 3 JSON Path Syntax For paths used in MySQL JSON functions, the scope is always the document being searched or otherwise operated on, represented by a leading $ character. – Akina Commented Mar 19 at 19:33

1 Answer 1

The $ symbol in MySQL JSON-related statements is used as a JSON path expression. JSON path expressions are used to specify the location of data within a JSON document. Here are the key details:

• JSON Path Expression: The $ symbol represents the root of the JSON document. It is used to navigate within the JSON structure.

  ex:

  • set jsonData = JSON_ARRAY_APPEND(coalesce(jsonData, '[]'), '$', JSON_OBJECT('name', 'facility_id', 'old_value', '', 'new_value', NEW.facility_id));, -----> the $ symbol indicates that the new JSON object should be appended to the root array of the jsonData.

  • SELECT JSON_ARRAY_APPEND(@j, '$[1]', 1);, -----> the $[1] specifies the second element in the root array of the JSON document stored in the variable @j.

    For more info : MySQL JSON Functions Documentation