1.JSON_ARRAY_APPEND(json_doc, path, val[, path, val] ...)
在指定的数组的最后附加一个值，然后返回修改后的json_doc。JSON_APPEND函数已被弃用，功能和JSON_ARRAY_APPEND一样，已在8.0版本中删除。
mysql> SET @j = '["a", ["b", "c"], "d"]';
mysql> SELECT JSON_ARRAY_APPEND(@j, '$[1]', 1);
+----------------------------------+
| JSON_ARRAY_APPEND(@j, '$[1]', 1) |
+----------------------------------+
| ["a", ["b", "c", 1], "d"] |
+----------------------------------+
mysql> SELECT JSON_ARRAY_APPEND(@j, '$[0]', 2);
+----------------------------------+
| JSON_ARRAY_APPEND(@j, '$[0]', 2) |
+----------------------------------+
| [["a", 2], ["b", "c"], "d"] |
+----------------------------------+
mysql> SELECT JSON_ARRAY_APPEND(@j, '$[1][0]', 3);
+-------------------------------------+
| JSON_ARRAY_APPEND(@j, '$[1][0]', 3) |
+-------------------------------------+
| ["a", [["b", 3], "c"], "d"] |
+-------------------------------------+
mysql> SET @j = '{"a": 1, "b": [2, 3], "c": 4}';
mysql> SELECT JSON_ARRAY_APPEND(@j, '$.b', 'x');
+------------------------------------+
| JSON_ARRAY_APPEND(@j, '$.b', 'x') |
+------------------------------------+
| {"a": 1, "b": [2, 3, "x"], "c": 4} |
+------------------------------------+
mysql> SELECT JSON_ARRAY_APPEND(@j, '$.c', 'y');
+--------------------------------------+
| JSON_ARRAY_APPEND(@j, '$.c', 'y') |
+--------------------------------------+
| {"a": 1, "b": [2, 3], "c": [4, "y"]} |
+--------------------------------------+
mysql> SET @j = '{"a": 1}';
mysql> SELECT JSON_ARRAY_APPEND(@j, '$', 'z');
+---------------------------------+
| JSON_ARRAY_APPEND(@j, '$', 'z') |
+---------------------------------+
| [{"a": 1}, "z"] |
+---------------------------------+2.JSON_ARRAY_INSERT(json_doc, path, val[, path, val] ...)
向指定的位置（path）插入值（val），返回更新后的json_doc。
mysql> SET @j = '["a", {"b": [1, 2]}, [3, 4]]';
mysql> SELECT JSON_ARRAY_INSERT(@j, '$[1]', 'x');
+------------------------------------+
| JSON_ARRAY_INSERT(@j, '$[1]', 'x') |
+------------------------------------+
| ["a", "x", {"b": [1, 2]}, [3, 4]] |
+------------------------------------+
mysql> SELECT JSON_ARRAY_INSERT(@j, '$[100]', 'x');
+--------------------------------------+
| JSON_ARRAY_INSERT(@j, '$[100]', 'x') |
+--------------------------------------+
| ["a", {"b": [1, 2]}, [3, 4], "x"] |
+--------------------------------------+
mysql> SELECT JSON_ARRAY_INSERT(@j, '$[1].b[0]', 'x');
+-----------------------------------------+
| JSON_ARRAY_INSERT(@j, '$[1].b[0]', 'x') |
+-----------------------------------------+
| ["a", {"b": ["x", 1, 2]}, [3, 4]] |
+-----------------------------------------+
mysql> SELECT JSON_ARRAY_INSERT(@j, '$[2][1]', 'y');
+---------------------------------------+
| JSON_ARRAY_INSERT(@j, '$[2][1]', 'y') |
+---------------------------------------+
| ["a", {"b": [1, 2]}, [3, "y", 4]] |
+---------------------------------------+
mysql> SELECT JSON_ARRAY_INSERT(@j, '$[0]', 'x', '$[2][1]', 'y');
+----------------------------------------------------+
| JSON_ARRAY_INSERT(@j, '$[0]', 'x', '$[2][1]', 'y') |
+----------------------------------------------------+
| ["x", "a", {"b": [1, 2]}, [3, 4]] |
+----------------------------------------------------+在最后一个sql语句中，因为执行完插入'$[0]', 'x'的操作后'$[2][1]'的路径并不存在了，所以，第二条插入并没有起到什么效果。
3.JSON_INSERT(json_doc, path, val[, path, val] ...)
如果不存在则插入新值，如果存在则不作操作。
mysql> SET @j = '{ "a": 1, "b": [2, 3]}';
mysql> SELECT JSON_INSERT(@j, '$.a', 10, '$.c', '[true, false]');
+----------------------------------------------------+
| JSON_INSERT(@j, '$.a', 10, '$.c', '[true, false]') |
+----------------------------------------------------+
| {"a": 1, "b": [2, 3], "c": "[true, false]"} |
+----------------------------------------------------+可以看到上面的结果中，c的值是个字符串而不是JSON数组，因为它被引用了。如果要变成JSON数组，要做如下修改
mysql> SELECT JSON_INSERT(@j, '$.a', 10, '$.c', CAST('[true, false]' AS JSON));
+------------------------------------------------------------------+
| JSON_INSERT(@j, '$.a', 10, '$.c', CAST('[true, false]' AS JSON)) |
+------------------------------------------------------------------+
| {"a": 1, "b": [2, 3], "c": [true, false]} |
+------------------------------------------------------------------+
1 row in set (0.00 sec)4.JSON_MERGE_PATCH(json_doc, json_doc[, json_doc] ...)
前面已经介绍过：https://www.hhfate.cn/t/617
5.JSON_MERGE_PRESERVE(json_doc, json_doc[, json_doc] ...)
该函数相较于JSON_MERGE_PATCH，不会后值不会覆盖前值，而是把相同key的值组成一个JSON数组。
mysql> SELECT JSON_MERGE_PRESERVE('[1, 2]', '[true, false]');
+------------------------------------------------+
| JSON_MERGE_PRESERVE('[1, 2]', '[true, false]') |
+------------------------------------------------+
| [1, 2, true, false] |
+------------------------------------------------+
mysql> SELECT JSON_MERGE_PRESERVE('{"name": "x"}', '{"id": 47}');
+----------------------------------------------------+
| JSON_MERGE_PRESERVE('{"name": "x"}', '{"id": 47}') |
+----------------------------------------------------+
| {"id": 47, "name": "x"} |
+----------------------------------------------------+
mysql> SELECT JSON_MERGE_PRESERVE('1', 'true');
+----------------------------------+
| JSON_MERGE_PRESERVE('1', 'true') |
+----------------------------------+
| [1, true] |
+----------------------------------+
mysql> SELECT JSON_MERGE_PRESERVE('[1, 2]', '{"id": 47}');
+---------------------------------------------+
| JSON_MERGE_PRESERVE('[1, 2]', '{"id": 47}') |
+---------------------------------------------+
| [1, 2, {"id": 47}] |
+---------------------------------------------+
mysql> SELECT JSON_MERGE_PRESERVE('{ "a": 1, "b": 2 }',
> '{ "a": 3, "c": 4 }');
+--------------------------------------------------------------+
| JSON_MERGE_PRESERVE('{ "a": 1, "b": 2 }','{ "a": 3, "c":4 }') |
+--------------------------------------------------------------+
| {"a": [1, 3], "b": 2, "c": 4} |
+--------------------------------------------------------------+
mysql> SELECT JSON_MERGE_PRESERVE('{ "a": 1, "b": 2 }','{ "a": 3, "c": 4 }',
> '{ "a": 5, "d": 6 }');
+----------------------------------------------------------------------------------+
| JSON_MERGE_PRESERVE('{ "a": 1, "b": 2 }','{ "a": 3, "c": 4 }','{ "a": 5, "d": 6 }') |
+----------------------------------------------------------------------------------+
| {"a": [1, 3, 5], "b": 2, "c": 4, "d": 6} |
+----------------------------------------------------------------------------------+6.JSON_REMOVE(json_doc, path[, path] ...)
删除节点，嗯，这个很容易理解。如果path不存在，则不作操作。
mysql> SET @j = '["a", ["b", "c"], "d"]'; mysql> SELECT JSON_REMOVE(@j, '$[1]'); +-------------------------+ | JSON_REMOVE(@j, '$[1]') | +-------------------------+ | ["a", "d"] | +-------------------------+
7.JSON_REPLACE(json_doc, path, val[, path, val] ...)
替换对应路径的值，只对存在的key有效。
mysql> SET @j = '{ "a": 1, "b": [2, 3]}';
mysql> SELECT JSON_REPLACE(@j, '$.a', 10, '$.c', '[true, false]');
+-----------------------------------------------------+
| JSON_REPLACE(@j, '$.a', 10, '$.c', '[true, false]') |
+-----------------------------------------------------+
| {"a": 10, "b": [2, 3]} |
+-----------------------------------------------------+8.JSON_SET(json_doc, path, val[, path, val] ...)
如果存在，则覆盖值；如果不存在，则新增值。
下面是 JSON_SET(), JSON_INSERT(), JSON_REPLACE()三个函数的比较：
JSON_SET() 替换现有值，添加新值
JSON_INSERT() 新加新值，不会替换现有值
JSON_REPLACE() 只替换现有值
mysql> SET @j = '{ "a": 1, "b": [2, 3]}';
mysql> SELECT JSON_SET(@j, '$.a', 10, '$.c', '[true, false]');
+-------------------------------------------------+
| JSON_SET(@j, '$.a', 10, '$.c', '[true, false]') |
+-------------------------------------------------+
| {"a": 10, "b": [2, 3], "c": "[true, false]"} |
+-------------------------------------------------+
mysql> SELECT JSON_INSERT(@j, '$.a', 10, '$.c', '[true, false]');
+----------------------------------------------------+
| JSON_INSERT(@j, '$.a', 10, '$.c', '[true, false]') |
+----------------------------------------------------+
| {"a": 1, "b": [2, 3], "c": "[true, false]"} |
+----------------------------------------------------+
mysql> SELECT JSON_REPLACE(@j, '$.a', 10, '$.c', '[true, false]');
+-----------------------------------------------------+
| JSON_REPLACE(@j, '$.a', 10, '$.c', '[true, false]') |
+-----------------------------------------------------+
| {"a": 10, "b": [2, 3]} |
+-----------------------------------------------------+9.JSON_UNQUOTE(json_val)
很简单，去掉引用（引号），返回一个utf8mb4格式的字符串。
mysql> SET @j = '"abc"'; mysql> SELECT @j, JSON_UNQUOTE(@j); +-------+------------------+ | @j | JSON_UNQUOTE(@j) | +-------+------------------+ | "abc" | abc | +-------+------------------+ mysql> SET @j = '[1, 2, 3]'; mysql> SELECT @j, JSON_UNQUOTE(@j); +-----------+------------------+ | @j | JSON_UNQUOTE(@j) | +-----------+------------------+ | [1, 2, 3] | [1, 2, 3] | +-----------+------------------+
一些转义符的处理：
| 转义符 | 反引用后的字符 |
| \" | 双引号 |
| \b | 退格符 |
| \f | 换页符 |
| \n | 换行符 |
| \r | 回车符 |
| \t | tab符 |
| \\ | 反斜杠（\） |
| \uXXXX | Unicode解码后的内容 |
mysql> SELECT @@sql_mode;
+------------+
| @@sql_mode |
+------------+
| |
+------------+
mysql> SELECT JSON_UNQUOTE('"\\t\\u0032"');
+------------------------------+
| JSON_UNQUOTE('"\\t\\u0032"') |
+------------------------------+
| 2 |
+------------------------------+
mysql> SET @@sql_mode = 'NO_BACKSLASH_ESCAPES';
mysql> SELECT JSON_UNQUOTE('"\\t\\u0032"');
+------------------------------+
| JSON_UNQUOTE('"\\t\\u0032"') |
+------------------------------+
| \t\u0032 |
+------------------------------+
mysql> SELECT JSON_UNQUOTE('"\t\u0032"');
+----------------------------+
| JSON_UNQUOTE('"\t\u0032"') |
+----------------------------+
| 2 |
+----------------------------+