MySQL 5.7 新特性之 JSON

时间 2019-11-08

标签 mysql 5.7 特性 json 栏目 MySQL 繁體版

原文原文链接

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

建立 JSON

相似 varchar，设置 JSON 主要将字段的 type 是 json, 不能设置长度，能够是 NULL 但不能有默认值。mysql

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

mysql> DESC tb_json_test;
+----------+------------------+------+-----+---------+----------------+
| 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 的字段就建立好了。json

插入 JSON

就是插入 json 格式的字符串，能够是对象的形式，也能够是数组的形式数组

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

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

mysql> INSERT INTO `tb_json_test` (category, tags) VALUES (JSON_OBJECT("id", 2, "name", "banana"), JSON_ARRAY(1, 3, 5));
Query OK, 1 row affected (0.00 sec)ui

查看插入的数据url

mysql> SELECT * FROM tb_json_test;
+----+------------------------------+-----------+
| id | category                     | tags      |
+----+------------------------------+-----------+
|  1 | {"id": 1, "name": "apple"}   | [1, 2, 3] |
|  2 | {"id": 2, "name": "banana"}  | [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.htmlspa

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 tb_json_test;
+----+------------------+--------------------+--------------+--------------+
| id | category->'$.id' | category->'$.name' | tags->'$[0]' | tags->'$[2]' |
+----+------------------+--------------------+--------------+--------------+
|  1 | 1                | "apple"            | 1            | 3            |
|  2 | 2                | "banana"           | 1            | 5            |
+----+------------------+--------------------+--------------+--------------+
2 rows in set (0.00 sec)

能够看到对应字符串类型的 category->'$.name' 中还包含着双引号，这其实并非想要的结果，能够用 JSON_UNQUOTE 函数将双引号去掉，从 MySQL 5.7.13 起也能够经过这个操做符 ->> 这个和 JSON_UNQUOTE 是等价的

mysql> SELECT id, category->'$.name', JSON_UNQUOTE(category->'$.name'), category->>'$.name' FROM tb_json_test;
+----+--------------------+----------------------------------+---------------------+
| id | category->'$.name' | JSON_UNQUOTE(category->'$.name') | category->>'$.name' |
+----+--------------------+----------------------------------+---------------------+
|  1 | "apple"            | apple                            | apple               |
|  2 | "banana"           | banana                           | banana              |
+----+--------------------+----------------------------------+---------------------+
2 rows in set (0.00 sec)

下面说下 JSON 做为条件进行搜索。由于 JSON 不一样于字符串，因此若是用字符串和 JSON 字段比较，是不会相等的

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

这时能够经过 CAST 将字符串转成 JSON 的形式

mysql> SELECT * FROM tb_json_test 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)

经过 JSON 中的元素进行查询, 对象型的查询一样能够经过 column->path

mysql> SELECT * FROM tb_json_test WHERE category->'$.name' = 'apple';
+----+------------------------------+-----------+
| id | category                     | tags      |
+----+------------------------------+-----------+
|  1 | {"id": 1, "name": "apple"}   | [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，但做为条件这里其实没什么影响，-> 和 ->> 结果是同样的

mysql> SELECT * FROM tb_json_test WHERE category->>'$.name' = 'apple';
+----+------------------------------+-----------+
| id | category                     | tags      |
+----+------------------------------+-----------+
|  1 | {"id": 1, "name": "apple"}   | [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，好比说整型和字符串是严格区分的

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

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

能够看到搜索字符串 1 和整型 1 的结果是不同的。

除了用 column->path 的形式搜索，还能够用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，不管 json 元素是整型仍是字符串，不然会出现这个错误

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

对于数组类型的 JSON 的查询，好比说 tags 中包含有 2 的数据，一样要用 JSON_CONTAINS 函数，一样第二个参数也须要是字符串

mysql> SELECT * FROM tb_json_test WHERE JSON_CONTAINS(tags, '2');
+----+------------------------------+-----------+
| id | category                     | tags      |
+----+------------------------------+-----------+
|  1 | {"id": 1, "name": "apple"}   | [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

若是是整个 json 更新的话，和插入时相似的。

mysql> UPDATE tb_json_test 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 tb_json_test ;
+----+------------------------------+-----------+ 
| id | category                     | tags      | 
+----+------------------------------+-----------+ 
| 1  | {"id": 1, "name": "apple"}   | [1, 3, 4] | 
| 2  | {"id": 2, "name": "banana"}  | [1, 3, 5] |
+----+------------------------------+-----------+
2 rows in set (0.00 sec)

但若是要更新 JSON 下的元素，MySQL 并不支持 column->path 的形式

mysql> UPDATE lnmp SET category->'$.name' = 'pear', tags->'$[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 '->'$.name' = 'pear', tags->'$[0]' = 2 WHERE id = 1' at line 1

则可能要用到如下几个函数

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, '$.name', 'pear', '$.weight', '100') WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

mysql> SELECT * FROM tb_json_test;
+----+----------------------------------------------------+-----------+
| id | category                                           | tags      |
+----+----------------------------------------------------+-----------+
|  1 | {"id": 1, "weight": "100", "name": "apple"}        | [1, 3, 4] |
|  2 | {"id": 2, "name": "banana"}                        | [1, 3, 5] |
+----+----------------------------------------------------+-----------+
2 rows in set (0.00 sec)

能够看到 name 没有被修改，但新元素 weight 已经添加进去

JSON_SET() 插入新值，并覆盖已经存在的值

mysql> UPDATE tb_json_test SET category = JSON_SET(category, '$.color', 'yellow', '$.weight', '200') WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

mysql> SELECT * FROM tb_json_test;
+----+----------------------------------------------------------------------------------+-----------+
| id | category                                                                         | tags      |
+----+----------------------------------------------------------------------------------+-----------+
|  1 | {"id": 1, "weight": "200", "color": "yellow", "name": "apple"}                   | [1, 3, 4] |
|  2 | {"id": 2, "name": "banana"}                                                      | [1, 3, 5] |
+----+----------------------------------------------------------------------------------+-----------+
2 rows in set (0.00 sec)

能够看到 color已经插入，weight已经被修改

JSON_REPLACE() 只替换存在的值

mysql> UPDATE tb_json_test SET category = JSON_REPLACE(category, '$.name', 'orange', '$.weight', '150') 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": "orange"}                                                         | [1, 3, 5] |
+----+----------------------------------------------------------------------------------+-----------+
2 rows in set (0.00 sec)

能够看到 name 已经被替换，weight 不存在被忽略。

JSON_REMOVE() 删除 JSON 元素

mysql> UPDATE tb_json_test SET category = JSON_REMOVE(category, '$.weight', '$.color') 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": "apple"}   | [1, 3, 4] |
|  2 | {"id": 2, "name": "banana"}  | [1, 3, 5] |
+----+------------------------------+-----------+
2 rows in set (0.00 sec)