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

Example 20-7 illustrates the equivalence: the two SELECT statements have the same effect.

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

In particular, if you use json_value more than once, or you use it in combination with json_exists 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 json_value(column, json_path 
                  RETURNING data_type error_hander ON ERROR)
  FROM table;

SELECT jt.column_alias
  FROM table,
       json_table(column, '$' error_handler ON ERROR
         COLUMNS ("COLUMN_ALIAS" data_type PATH json_path)) AS "JT";