SQL/JSON condition json_exists can be viewed as a special case of SQL/JSON function json_table.

Example 19-6 illustrates the equivalence: the two SELECT statements have the same effect.

In addition to perhaps helping you understand json_exists better, this equivalence is important practically, because it means that you can use either to get the same effect.

In particular, if you use json_exists more than once, or you use it in combination with json_value or json_query (which can also be expressed using json_table), to access the same data, then a single invocation of json_table presents the advantage that the data is parsed only once.

Because of this, the optimizer often automatically rewrites multiple invocations of json_exists, json_value and json_query (any combination) to fewer invocations of json_table.

SELECT select_list
  FROM table WHERE json_exists(column, 
                               json_path error_handler ON ERROR);
       
SELECT select_list
  FROM table,
       json_table(column, '$' error_handler ON ERROR
         COLUMNS ("COLUMN_ALIAS" NUMBER EXISTS PATH json_path)) AS "JT"
  WHERE jt.column_alias = 1;