MySQL處理JSON常見函數的使用

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官方文檔：JSON Functions

Name Description
JSON_APPEND() Append data to JSON document
JSON_ARRAY() Create JSON array
JSON_ARRAY_APPEND() Append data to JSON document
JSON_ARRAY_INSERT() Insert into JSON array
-> Return value from JSON column after evaluating path; equivalent to JSON_EXTRACT().
JSON_CONTAINS() Whether JSON document contains specific object at path
JSON_CONTAINS_PATH() Whether JSON document contains any data at path
JSON_DEPTH() Maximum depth of JSON document
JSON_EXTRACT() Return data from JSON document
->> Return value from JSON column after evaluating path and unquoting the result; equivalent to JSON_UNQUOTE(JSON_EXTRACT()).
JSON_INSERT() Insert data into JSON document
JSON_KEYS() Array of keys from JSON document
JSON_LENGTH() Number of elements in JSON document
JSON_MERGE() Merge JSON documents
JSON_OBJECT() Create JSON object
JSON_QUOTE() Quote JSON document
JSON_REMOVE() Remove data from JSON document
JSON_REPLACE() Replace values in JSON document
JSON_SEARCH() Path to value within JSON document
JSON_SET() Insert data into JSON document
JSON_TYPE() Type of JSON value
JSON_UNQUOTE() Unquote JSON value
JSON_VALID() Whether JSON value is valid

1. 概述

MySQL裡的json分為json array和json object。 $表示整個json對象，在索引數據時用下標(對於json array，從0開始)或鍵值(對於json object，含有特殊字符的key要用”括起來，比如$.”my name”)。

例如：[3, {“a”: [5, 6], “b”: 10}, [99, 100]]，那麼：

$[0]：3

$[1]： {“a”: [5, 6], “b”: 10}

$[2] ：[99, 100]

$[3] ： NULL

$[1].a：[5, 6]

$[1].a[1]：6

$[1].b：10

$[2][0]：99

2. 比較規則

json中的數據可以用 =, <, <=, >, >=, <>, !=, and <=> 進行比較。但json裡的數據類型可以是多樣的，那麼在不同類型之間進行比較時，就有優先級瞭，高優先級的要大於低優先級的（可以用JSON_TYPE()函數查看類型）。優先級從高到低如下：

 BLOB
BIT
OPAQUE
DATETIME
TIME
DATE
BOOLEAN
ARRAY
OBJECT
STRING
INTEGER, DOUBLE
NULL　

3. 常用函數

3.1 創建函數

3.1.1 JSON_ARRAY

JSON_ARRAY(val1,val2,val3…)

生成一個包含指定元素的json數組。

mysql> SELECT JSON_ARRAY(1, "abc", NULL, TRUE, CURTIME());
+---------------------------------------------+
| JSON_ARRAY(1, "abc", NULL, TRUE, CURTIME()) |
+---------------------------------------------+
| [1, "abc", null, true, "11:30:24.000000"]  |
+---------------------------------------------+

3.1.2 JSON_OBJECT

JSON_OBJECT(key1,val1,key2,val2…)

生成一個包含指定K-V對的json object。如果有key為NULL或參數個數為奇數，則拋錯。

mysql> SELECT JSON_OBJECT('id', 87, 'name', 'carrot');
+-----------------------------------------+
| JSON_OBJECT('id', 87, 'name', 'carrot') |
+-----------------------------------------+
| {"id": 87, "name": "carrot"}      |
+-----------------------------------------+

3.1.3 JSON_QUOTE

JSON_QUOTE(json_val)

將json_val用”號括起來。

mysql> SELECT JSON_QUOTE('null'), JSON_QUOTE('"null"');
+--------------------+----------------------+
| JSON_QUOTE('null') | JSON_QUOTE('"null"') |
+--------------------+----------------------+
| "null"       | "\"null\""      |
+--------------------+----------------------+
mysql> SELECT JSON_QUOTE('[1, 2, 3]');
+-------------------------+
| JSON_QUOTE('[1, 2, 3]') |
+-------------------------+
| "[1, 2, 3]"       |
+-------------------------+

3.1.4 CONVERT

CONVERT(json_string,JSON)

mysql> select CONVERT('{"mail": "[email protected]", "name": "Amy"}',JSON);
+----------------------------------------------------------+
| CONVERT('{"mail": "[email protected]", "name": "Amy"}',JSON) |
+----------------------------------------------------------+
| {"mail": "[email protected]", "name": "Amy"}         |
+----------------------------------------------------------+

3.2 查詢函數　　

3.2.1 JSON_CONTAINS

JSON_CONTAINS(json_doc, val[, path])

查詢json文檔是否在指定path包含指定的數據，包含則返回1，否則返回0。如果有參數為NULL或path不存在，則返回NULL。

mysql> SET @j = '{"a": 1, "b": 2, "c": {"d": 4}}';
mysql> SET @j2 = '1';
mysql> SELECT JSON_CONTAINS(@j, @j2, '$.a');
+-------------------------------+
| JSON_CONTAINS(@j, @j2, '$.a') |
+-------------------------------+
|               1 |
+-------------------------------+
mysql> SELECT JSON_CONTAINS(@j, @j2, '$.b');
+-------------------------------+
| JSON_CONTAINS(@j, @j2, '$.b') |
+-------------------------------+
|               0 |
+-------------------------------+
 
mysql> SET @j2 = '{"d": 4}';
mysql> SELECT JSON_CONTAINS(@j, @j2, '$.a');
+-------------------------------+
| JSON_CONTAINS(@j, @j2, '$.a') |
+-------------------------------+
|               0 |
+-------------------------------+
mysql> SELECT JSON_CONTAINS(@j, @j2, '$.c');
+-------------------------------+
| JSON_CONTAINS(@j, @j2, '$.c') |
+-------------------------------+
|               1 |
+-------------------------------+

3.2.2 JSON_CONTAINS_PATH

JSON_CONTAINS_PATH(json_doc, one_or_all, path[, path] …)

查詢是否存在指定路徑，存在則返回1，否則返回0。如果有參數為NULL，則返回NULL。

one_or_all隻能取值”one”或”all”，one表示隻要有一個存在即可；all表示所有的都存在才行。

mysql> SET @j = '{"a": 1, "b": 2, "c": {"d": 4}}';
mysql> SELECT JSON_CONTAINS_PATH(@j, 'one', '$.a', '$.e');
+---------------------------------------------+
| JSON_CONTAINS_PATH(@j, 'one', '$.a', '$.e') |
+---------------------------------------------+
|                      1 |
+---------------------------------------------+
mysql> SELECT JSON_CONTAINS_PATH(@j, 'all', '$.a', '$.e');
+---------------------------------------------+
| JSON_CONTAINS_PATH(@j, 'all', '$.a', '$.e') |
+---------------------------------------------+
|                      0 |
+---------------------------------------------+
mysql> SELECT JSON_CONTAINS_PATH(@j, 'one', '$.c.d');
+----------------------------------------+
| JSON_CONTAINS_PATH(@j, 'one', '$.c.d') |
+----------------------------------------+
|                   1 |
+----------------------------------------+
mysql> SELECT JSON_CONTAINS_PATH(@j, 'one', '$.a.d');
+----------------------------------------+
| JSON_CONTAINS_PATH(@j, 'one', '$.a.d') |
+----------------------------------------+
|                   0 |
+----------------------------------------+

3.2.3 JSON_EXTRACT

JSON_EXTRACT(json_doc, path[, path] …)

從json文檔裡抽取數據。如果有參數有NULL或path不存在，則返回NULL。如果抽取出多個path，則返回的數據封閉在一個json array裡。

mysql> SELECT JSON_EXTRACT('[10, 20, [30, 40]]', '$[1]');
+--------------------------------------------+
| JSON_EXTRACT('[10, 20, [30, 40]]', '$[1]') |
+--------------------------------------------+
| 20                     |
+--------------------------------------------+
mysql> SELECT JSON_EXTRACT('[10, 20, [30, 40]]', '$[1]', '$[0]');
+----------------------------------------------------+
| JSON_EXTRACT('[10, 20, [30, 40]]', '$[1]', '$[0]') |
+----------------------------------------------------+
| [20, 10]                      |
+----------------------------------------------------+
mysql> SELECT JSON_EXTRACT('[10, 20, [30, 40]]', '$[2][*]');
+-----------------------------------------------+
| JSON_EXTRACT('[10, 20, [30, 40]]', '$[2][*]') |
+-----------------------------------------------+
| [30, 40]                   |
+-----------------------------------------------+

在MySQL 5.7.9+裡可以用”->”替代。

mysql> SELECT c, JSON_EXTRACT(c, "$.id"), g
   > FROM jemp
   > WHERE JSON_EXTRACT(c, "$.id") > 1
   > ORDER BY JSON_EXTRACT(c, "$.name");
+-------------------------------+-----------+------+
| c               | c->"$.id" | g  |
+-------------------------------+-----------+------+
| {"id": "3", "name": "Barney"} | "3"    |  3 |
| {"id": "4", "name": "Betty"} | "4"    |  4 |
| {"id": "2", "name": "Wilma"} | "2"    |  2 |
+-------------------------------+-----------+------+
3 rows in set (0.00 sec)
 
mysql> SELECT c, c->"$.id", g
   > FROM jemp
   > WHERE c->"$.id" > 1
   > ORDER BY c->"$.name";
+-------------------------------+-----------+------+
| c               | c->"$.id" | g  |
+-------------------------------+-----------+------+
| {"id": "3", "name": "Barney"} | "3"    |  3 |
| {"id": "4", "name": "Betty"} | "4"    |  4 |
| {"id": "2", "name": "Wilma"} | "2"    |  2 |
+-------------------------------+-----------+------+
3 rows in set (0.00 sec)

在MySQL 5.7.13+，還可以用”->>”表示去掉抽取結果的”號，下面三種效果是一樣的：

  • JSON_UNQUOTE( JSON_EXTRACT(column, path) )
  • JSON_UNQUOTE(column -> path)
  • column->>path
mysql> SELECT * FROM jemp WHERE g > 2;
+-------------------------------+------+
| c               | g  |
+-------------------------------+------+
| {"id": "3", "name": "Barney"} |  3 |
| {"id": "4", "name": "Betty"} |  4 |
+-------------------------------+------+
2 rows in set (0.01 sec)
 
mysql> SELECT c->'$.name' AS name  
  ->   FROM jemp WHERE g > 2;
+----------+
| name   |
+----------+
| "Barney" |
| "Betty" |
+----------+
2 rows in set (0.00 sec)
 
mysql> SELECT JSON_UNQUOTE(c->'$.name') AS name
  ->   FROM jemp WHERE g > 2;
+--------+
| name  |
+--------+
| Barney |
| Betty |
+--------+
2 rows in set (0.00 sec)
 
mysql> SELECT c->>'$.name' AS name
  ->   FROM jemp WHERE g > 2;
+--------+
| name  |
+--------+
| Barney |
| Betty |
+--------+
2 rows in set (0.00 sec)

3.2.4 JSON_KEYS

JSON_KEYS(json_doc[, path])

獲取json文檔在指定路徑下的所有鍵值，返回一個json array。如果有參數為NULL或path不存在，則返回NULL。

mysql> SELECT JSON_KEYS('{"a": 1, "b": {"c": 30}}');
+---------------------------------------+
| JSON_KEYS('{"a": 1, "b": {"c": 30}}') |
+---------------------------------------+
| ["a", "b"]              |
+---------------------------------------+
mysql> SELECT JSON_KEYS('{"a": 1, "b": {"c": 30}}', '$.b');
+----------------------------------------------+
| JSON_KEYS('{"a": 1, "b": {"c": 30}}', '$.b') |
+----------------------------------------------+
| ["c"]                    |
+----------------------------------------------+

3.2.5 JSON_SEARCH

JSON_SEARCH(json_doc, one_or_all, search_str[, escape_char[, path] …])

查詢包含指定字符串的paths，並作為一個json array返回。如果有參數為NUL或path不存在，則返回NULL。

  • one_or_all：”one”表示查詢到一個即返回；”all”表示查詢所有。
  • search_str：要查詢的字符串。 可以用LIKE裡的’%’或‘_’匹配。
  • path：在指定path下查。
mysql> SET @j = '["abc", [{"k": "10"}, "def"], {"x":"abc"}, {"y":"bcd"}]';
 
mysql> SELECT JSON_SEARCH(@j, 'one', 'abc');
+-------------------------------+
| JSON_SEARCH(@j, 'one', 'abc') |
+-------------------------------+
| "$[0]"            |
+-------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', 'abc');
+-------------------------------+
| JSON_SEARCH(@j, 'all', 'abc') |
+-------------------------------+
| ["$[0]", "$[2].x"]      |
+-------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', 'ghi');
+-------------------------------+
| JSON_SEARCH(@j, 'all', 'ghi') |
+-------------------------------+
| NULL             |
+-------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '10');
+------------------------------+
| JSON_SEARCH(@j, 'all', '10') |
+------------------------------+
| "$[1][0].k"         |
+------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '10', NULL, '$');
+-----------------------------------------+
| JSON_SEARCH(@j, 'all', '10', NULL, '$') |
+-----------------------------------------+
| "$[1][0].k"               |
+-----------------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '10', NULL, '$[*]');
+--------------------------------------------+
| JSON_SEARCH(@j, 'all', '10', NULL, '$[*]') |
+--------------------------------------------+
| "$[1][0].k"                |
+--------------------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '10', NULL, '$**.k');
+---------------------------------------------+
| JSON_SEARCH(@j, 'all', '10', NULL, '$**.k') |
+---------------------------------------------+
| "$[1][0].k"                 |
+---------------------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '10', NULL, '$[*][0].k');
+-------------------------------------------------+
| JSON_SEARCH(@j, 'all', '10', NULL, '$[*][0].k') |
+-------------------------------------------------+
| "$[1][0].k"                   |
+-------------------------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '10', NULL, '$[1]');
+--------------------------------------------+
| JSON_SEARCH(@j, 'all', '10', NULL, '$[1]') |
+--------------------------------------------+
| "$[1][0].k"                |
+--------------------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '10', NULL, '$[1][0]');
+-----------------------------------------------+
| JSON_SEARCH(@j, 'all', '10', NULL, '$[1][0]') |
+-----------------------------------------------+
| "$[1][0].k"                  |
+-----------------------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', 'abc', NULL, '$[2]');
+---------------------------------------------+
| JSON_SEARCH(@j, 'all', 'abc', NULL, '$[2]') |
+---------------------------------------------+
| "$[2].x"                  |
+---------------------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '%a%');
+-------------------------------+
| JSON_SEARCH(@j, 'all', '%a%') |
+-------------------------------+
| ["$[0]", "$[2].x"]      |
+-------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '%b%');
+-------------------------------+
| JSON_SEARCH(@j, 'all', '%b%') |
+-------------------------------+
| ["$[0]", "$[2].x", "$[3].y"] |
+-------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '%b%', NULL, '$[0]');
+---------------------------------------------+
| JSON_SEARCH(@j, 'all', '%b%', NULL, '$[0]') |
+---------------------------------------------+
| "$[0]"                   |
+---------------------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '%b%', NULL, '$[2]');
+---------------------------------------------+
| JSON_SEARCH(@j, 'all', '%b%', NULL, '$[2]') |
+---------------------------------------------+
| "$[2].x"                  |
+---------------------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '%b%', NULL, '$[1]');
+---------------------------------------------+
| JSON_SEARCH(@j, 'all', '%b%', NULL, '$[1]') |
+---------------------------------------------+
| NULL                    |
+---------------------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '%b%', '', '$[1]');
+-------------------------------------------+
| JSON_SEARCH(@j, 'all', '%b%', '', '$[1]') |
+-------------------------------------------+
| NULL                   |
+-------------------------------------------+
 
mysql> SELECT JSON_SEARCH(@j, 'all', '%b%', '', '$[3]');
+-------------------------------------------+
| JSON_SEARCH(@j, 'all', '%b%', '', '$[3]') |
+-------------------------------------------+
| "$[3].y"                 |
+-------------------------------------------+

3.3 修改函數

3.3.1 JSON_APPEND/JSON_ARRAY_APPEND

JSON_ARRAY_APPEND(json_doc, path, val[, path, val] …)

在指定path的json array尾部追加val。如果指定path是一個json object，則將其封裝成一個json array再追加。如果有參數為NULL，則返回NULL。

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"]         |
+---------------------------------+

3.3.2 JSON_ARRAY_INSERT

JSON_ARRAY_INSERT(json_doc, path, val[, path, val] …)

在path指定的json array元素插入val，原位置及以右的元素順次右移。如果path指定的數據非json array元素，則略過此val；如果指定的元素下標超過json array的長度，則插入尾部。

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]]         |
+----------------------------------------------------+

3.3.3 JSON_INSERT/JSON_REPLACE/JSON_SET

JSON_INSERT(json_doc, path, val[, path, val] …)

在指定path下插入數據，如果path已存在，則忽略此val（不存在才插入）。

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]"}    |
+----------------------------------------------------+

JSON_REPLACE(json_doc, path, val[, path, val] …)

替換指定路徑的數據，如果某個路徑不存在則略過（存在才替換）。如果有參數為NULL，則返回NULL。

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]}               |
+-----------------------------------------------------+

JSON_SET(json_doc, path, val[, path, val] …)

設置指定路徑的數據（不管是否存在）。如果有參數為NULL，則返回NULL。

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]}               |
+-----------------------------------------------------+

3.3.4 JSON_MERGE

JSON_MERGE(json_doc, json_doc[, json_doc] …)

merge多個json文檔。規則如下：

  • 如果都是json array，則結果自動merge為一個json array；
  • 如果都是json object，則結果自動merge為一個json object；
  • 如果有多種類型，則將非json array的元素封裝成json array再按照規則一進行mege。
mysql> SELECT JSON_MERGE('[1, 2]', '[true, false]');
+---------------------------------------+
| JSON_MERGE('[1, 2]', '[true, false]') |
+---------------------------------------+
| [1, 2, true, false]          |
+---------------------------------------+
mysql> SELECT JSON_MERGE('{"name": "x"}', '{"id": 47}');
+-------------------------------------------+
| JSON_MERGE('{"name": "x"}', '{"id": 47}') |
+-------------------------------------------+
| {"id": 47, "name": "x"}          |
+-------------------------------------------+
mysql> SELECT JSON_MERGE('1', 'true');
+-------------------------+
| JSON_MERGE('1', 'true') |
+-------------------------+
| [1, true]        |
+-------------------------+
mysql> SELECT JSON_MERGE('[1, 2]', '{"id": 47}');
+------------------------------------+
| JSON_MERGE('[1, 2]', '{"id": 47}') |
+------------------------------------+
| [1, 2, {"id": 47}]         |
+------------------------------------+

3.3.5 JSON_REMOVE

JSON_REMOVE(json_doc, path[, path] …)

移除指定路徑的數據，如果某個路徑不存在則略過此路徑。如果有參數為NULL，則返回NULL。

mysql> SET @j = '["a", ["b", "c"], "d"]';
mysql> SELECT JSON_REMOVE(@j, '$[1]');
+-------------------------+
| JSON_REMOVE(@j, '$[1]') |
+-------------------------+
| ["a", "d"]       |
+-------------------------+

3.3.6 JSON_UNQUOTE

JSON_UNQUOTE(val)

去掉val的引號。如果val為NULL，則返回NULL。

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]    |
+-----------+------------------+

3.4 JSON特性查詢

3.4.1 JSON_DEEPTH

JSON_DEPTH(json_doc)

獲取json文檔的深度。如果參數為NULL，則返回NULL。

空的json array、json object或標量的深度為1。

mysql> SELECT JSON_DEPTH('{}'), JSON_DEPTH('[]'), JSON_DEPTH('true');
+------------------+------------------+--------------------+
| JSON_DEPTH('{}') | JSON_DEPTH('[]') | JSON_DEPTH('true') |
+------------------+------------------+--------------------+
|        1 |        1 |         1 |
+------------------+------------------+--------------------+
mysql> SELECT JSON_DEPTH('[10, 20]'), JSON_DEPTH('[[], {}]');
+------------------------+------------------------+
| JSON_DEPTH('[10, 20]') | JSON_DEPTH('[[], {}]') |
+------------------------+------------------------+
|           2 |           2 |
+------------------------+------------------------+
mysql> SELECT JSON_DEPTH('[10, {"a": 20}]');
+-------------------------------+
| JSON_DEPTH('[10, {"a": 20}]') |
+-------------------------------+
|               3 |
+-------------------------------+

3.4.2 JSON_LENGTH

JSON_LENGTH(json_doc[, path])

獲取指定路徑下的長度。如果參數為NULL，則返回NULL。　

長度的計算規則：

  • 標量的長度為1；
  • json array的長度為元素的個數；
  • json object的長度為key的個數。
mysql> SELECT JSON_LENGTH('[1, 2, {"a": 3}]');
+---------------------------------+
| JSON_LENGTH('[1, 2, {"a": 3}]') |
+---------------------------------+
|                3 |
+---------------------------------+
mysql> SELECT JSON_LENGTH('{"a": 1, "b": {"c": 30}}');
+-----------------------------------------+
| JSON_LENGTH('{"a": 1, "b": {"c": 30}}') |
+-----------------------------------------+
|                    2 |
+-----------------------------------------+
mysql> SELECT JSON_LENGTH('{"a": 1, "b": {"c": 30}}', '$.b');
+------------------------------------------------+
| JSON_LENGTH('{"a": 1, "b": {"c": 30}}', '$.b') |
+------------------------------------------------+
|                       1 |
+------------------------------------------------+

3.4.3 JSON_TYPE

JSON_TYPE(json_val)

獲取json文檔的具體類型。如果參數為NULL，則返回NULL。

3.4.4 JSON_VALID

JSON_VALID(val)

判斷val是否為有效的json格式，是為1，不是為0。如果參數為NUL，則返回NULL。

mysql> SELECT JSON_VALID('{"a": 1}');
+------------------------+
| JSON_VALID('{"a": 1}') |
+------------------------+
|           1 |
+------------------------+
mysql> SELECT JSON_VALID('hello'), JSON_VALID('"hello"');
+---------------------+-----------------------+
| JSON_VALID('hello') | JSON_VALID('"hello"') |
+---------------------+-----------------------+
|          0 |           1 |
+---------------------+-----------------------+

到此這篇關於MySQL處理JSON常見函數的使用的文章就介紹到這瞭,更多相關MySQL JSON常見函數內容請搜索WalkonNet以前的文章或繼續瀏覽下面的相關文章希望大傢以後多多支持WalkonNet！

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