从 MySQL 5.7.8 开始,MySQL 支持原生的 JSON 数据类型。

创建 JSON

类似 varchar,设置 JSON 主要将字段的 type 是 json, 不能设置长度,可以是 NULL  但不能有默认值。

mysql> CREATE TABLE lnmp (
    `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
    `category` JSON,
    `tags` JSON,
    PRIMARY KEY (`id`)
);

mysql> DESC lnmp;
+----------+------------------+------+-----+---------+----------------+
| Field    | Type             | Null | Key | Default | Extra          |
+----------+------------------+------+-----+---------+----------------+
| id       | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| category | json             | YES  |     | NULL    |                |
| tags     | json             | YES  |     | NULL    |                |
+----------+------------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)

这样 JSON 的字段就创建好了。

插入 JSON

就是插入 json 格式的字符串,可以是对象的形式,也可以是数组的形式

mysql> INSERT INTO `lnmp` (category, tags) VALUES ('{"id": 1, "name": "lnmp.cn"}', '[1, 2, 3]');
Query OK, 1 row affected (0.01 sec)

MySQL 也有专门的函数 JSON_OBJECT,JSON_ARRAY 生成 json 格式的数据

mysql> INSERT INTO `lnmp` (category, tags) VALUES (JSON_OBJECT("id", 2, "name", "php.net"), JSON_ARRAY(1, 3, 5));
Query OK, 1 row affected (0.00 sec)

查看插入的数据

mysql> SELECT * FROM lnmp;
+----+------------------------------+-----------+
| id | category                     | tags      |
+----+------------------------------+-----------+
|  1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
|  2 | {"id": 2, "name": "php.net"} | [1, 3, 5] |
+----+------------------------------+-----------+
2 rows in set (0.00 sec)

更多生成 JSON 值的函数请参考: http://dev.mysql.com/doc/refman/5.7/en/json-creation-functions.html

查询 JSON

查询 json 中的数据用 column->path 的形式,其中对象类型 path 这样表示 $.path, 而数组类型则是 $[index]

mysql> SELECT id, category->'$.id', category->'$.name', tags->'$[0]', tags->'$[2]' FROM lnmp;
+----+------------------+--------------------+--------------+--------------+
| id | category->'$.id' | category->'$.name' | tags->'$[0]' | tags->'$[2]' |
+----+------------------+--------------------+--------------+--------------+
|  1 | 1                | "lnmp.cn"          | 1            | 3            |
|  2 | 2                | "php.net"          | 1            | 5            |
+----+------------------+--------------------+--------------+--------------+
2 rows in set (0.00 sec)

可以看到对应字符串类型的 category->'$.name' 中还包含着双引号,这其实并不是想要的结果,可以用 JSON_UNQUOTE 函数将双引号去掉,从 MySQL 5.7.13 起也可以通过这个操作符 ->> 这个和 JSON_UNQUOTE 是等价的

mysql> SELECT id, category->'$.name', JSON_UNQUOTE(category->'$.name'), category->>'$.name' FROM lnmp;
+----+--------------------+----------------------------------+---------------------+
| id | category->'$.name' | JSON_UNQUOTE(category->'$.name') | category->>'$.name' |
+----+--------------------+----------------------------------+---------------------+
|  1 | "lnmp.cn"          | lnmp.cn                          | lnmp.cn             |
|  2 | "php.net"          | php.net                          | php.net             |
+----+--------------------+----------------------------------+---------------------+
2 rows in set (0.00 sec)

下面说下 JSON 作为条件进行搜索。因为 JSON 不同于字符串,所以如果用字符串和 JSON 字段比较,是不会相等的

mysql> SELECT * FROM lnmp WHERE category = '{"id": 1, "name": "lnmp.cn"}';
Empty set (0.00 sec)

这时可以通过 CAST 将字符串转成 JSON 的形式

mysql> SELECT * FROM lnmp WHERE category = CAST('{"id": 1, "name": "lnmp.cn"}' as JSON);
+----+------------------------------+-----------+
| id | category                     | tags      |
+----+------------------------------+-----------+
|  1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
+----+------------------------------+-----------+
1 row in set (0.00 sec)

通过 JSON 中的元素进行查询, 对象型的查询同样可以通过 column->path

mysql> SELECT * FROM lnmp WHERE category->'$.name' = 'lnmp.cn';
+----+------------------------------+-----------+
| id | category                     | tags      |
+----+------------------------------+-----------+
|  1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
+----+------------------------------+-----------+
1 row in set (0.00 sec)

上面有提到 column->path 形式从 select 中查询出来的字符串是包含双引号的,但作为条件这里其实没什么影响,-> 和 ->> 结果是一样的

mysql> SELECT * FROM lnmp WHERE category->>'$.name' = 'lnmp.cn';
+----+------------------------------+-----------+
| id | category                     | tags      |
+----+------------------------------+-----------+
|  1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
+----+------------------------------+-----------+
1 row in set (0.00 sec)

要特别注意的是,JSON 中的元素搜索是严格区分变量类型的,比如说整型和字符串是严格区分的

mysql> SELECT * FROM lnmp WHERE category->'$.id' = '1';
Empty set (0.00 sec)

mysql> SELECT * FROM lnmp WHERE category->'$.id' = 1;
+----+------------------------------+-----------+
| id | category                     | tags      |
+----+------------------------------+-----------+
|  1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
+----+------------------------------+-----------+
1 row in set (0.00 sec)

可以看到搜索字符串 1 和整型 1 的结果是不一样的。

除了用 column->path 的形式搜索,还可以用JSON_CONTAINS 函数,但和 column->path 的形式有点相反的是,JSON_CONTAINS 第二个参数是不接受整数的,无论 json 元素是整型还是字符串,否则会出现这个错误

mysql> SELECT * FROM lnmp WHERE JSON_CONTAINS(category, 1, '$.id');
ERROR 3146 (22032): Invalid data type for JSON data in argument 2 to function json_contains; a JSON string or JSON type is required.

这里必须是要字符串 1

mysql> SELECT * FROM lnmp WHERE JSON_CONTAINS(category, '1', '$.id');
+----+------------------------------+-----------+
| id | category                     | tags      |
+----+------------------------------+-----------+
|  1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
+----+------------------------------+-----------+
1 row in set (0.01 sec)

对于数组类型的 JSON 的查询,比如说 tags 中包含有 2 的数据,同样要用 JSON_CONTAINS 函数,同样第二个参数也需要是字符串

mysql> SELECT * FROM lnmp WHERE JSON_CONTAINS(tags, '2');
+----+------------------------------+-----------+
| id | category                     | tags      |
+----+------------------------------+-----------+
|  1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
+----+------------------------------+-----------+
1 row in set (0.00 sec)

更多搜索 JSON 值的函数请参考:http://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html

更新 JSON

如果是整个 json 更新的话,和插入时类似的。

mysql> UPDATE lnmp SET tags = '[1, 3, 4]' WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT * FROM lnmp;
+----+------------------------------+-----------+ 
| id | category                     | tags      | 
+----+------------------------------+-----------+ 
| 1  | {"id": 1, "name": "lnmp.cn"} | [1, 3, 4] | 
| 2  | {"id": 2, "name": "php.net"} | [1, 3, 5] |
+----+------------------------------+-----------+
2 rows in set (0.00 sec)

但如果要更新 JSON 下的元素,MySQL 并不支持 column->path 的形式

mysql> UPDATE lnmp SET category->'$.name' = 'lnmp', tags->'$[0]' = 2 WHERE id = 1;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '->'$.name' = 'lnmp', tags->'$[0]' = 2 WHERE id = 1' at line 1

则可能要用到以下几个函数

JSON_INSERT() 插入新值,但不会覆盖已经存在的值

mysql> UPDATE lnmp SET category = JSON_INSERT(category, '$.name', 'lnmp', '$.url', 'www.lnmp.cn') WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT * FROM lnmp;
+----+----------------------------------------------------+-----------+
| id | category                                           | tags      |
+----+----------------------------------------------------+-----------+
|  1 | {"id": 1, "url": "www.lnmp.cn", "name": "lnmp.cn"} | [1, 3, 4] |
|  2 | {"id": 2, "name": "php.net"}                       | [1, 3, 5] |
+----+----------------------------------------------------+-----------+
2 rows in set (0.00 sec)

可以看到 name 没有被修改,但新元素 url 已经添加进去

JSON_SET() 插入新值,并覆盖已经存在的值

mysql> UPDATE lnmp SET category = JSON_SET(category, '$.host', 'www.lnmp.cn', '$.url', 'http://www.lnmp.cn') WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT * FROM lnmp;
+----+----------------------------------------------------------------------------------+-----------+
| id | category                                                                         | tags      |
+----+----------------------------------------------------------------------------------+-----------+
|  1 | {"id": 1, "url": "http://www.lnmp.cn", "host": "www.lnmp.cn", "name": "lnmp.cn"} | [1, 3, 4] |
|  2 | {"id": 2, "name": "php.net"}                                                     | [1, 3, 5] |
+----+----------------------------------------------------------------------------------+-----------+
2 rows in set (0.00 sec)

可以看到 host 已经插入,url 已经被修改

JSON_REPLACE() 只替换存在的值

mysql> UPDATE lnmp SET category = JSON_REPLACE(category, '$.name', 'php', '$.url', 'http://www.php.net') WHERE id = 2;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT * FROM lnmp;
+----+----------------------------------------------------------------------------------+-----------+
| id | category                                                                         | tags      |
+----+----------------------------------------------------------------------------------+-----------+
|  1 | {"id": 1, "url": "http://www.lnmp.cn", "host": "www.lnmp.cn", "name": "lnmp.cn"} | [1, 3, 4] |
|  2 | {"id": 2, "name": "php"}                                                         | [1, 3, 5] |
+----+----------------------------------------------------------------------------------+-----------+
2 rows in set (0.00 sec)

可以看到 name 已经被替换,url 不存在被忽略。

JSON_REMOVE() 删除 JSON 元素

mysql> UPDATE lnmp SET category = JSON_REMOVE(category, '$.url', '$.host') WHERE id = 1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT * FROM lnmp;
+----+------------------------------+-----------+
| id | category                     | tags      |
+----+------------------------------+-----------+
|  1 | {"id": 1, "name": "lnmp.cn"} | [1, 3, 4] |
|  2 | {"id": 2, "name": "php"}     | [1, 3, 5] |
+----+------------------------------+-----------+
2 rows in set (0.00 sec)

更多函数请参考:http://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html

MySQL JSON 在 PHP 中的表现

虽然在 MySQL 是个JSON 类型,但实际在 PHP 应用中返回的是 JSON 格式的字符串

array(2) {
  [0]=>
  array(3) {
    ["id"]=>
    string(1) "1"
    ["category"]=>
    string(28) "{"id": 1, "name": "lnmp.cn"}"
    ["tags"]=>
    string(9) "[1, 3, 4]"
  }
  [1]=>
  array(3) {
    ["id"]=>
    string(1) "2"
    ["category"]=>
    string(24) "{"id": 2, "name": "php"}"
    ["tags"]=>
    string(9) "[1, 3, 5]"
  }
}
posted on 2018-06-14 20:37  lshan  阅读(196)  评论(0编辑  收藏  举报