mysql5.7新特性JSON數據類型解析
一、json結構
創建測試表
CREATE TABLE `article` ( `id` int(11) unsigned NOT NULL AUTO_INCREMENT, `category` json NOT NULL, `tags` json NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8
分析：article表中的字段category與tags均為json類型
填寫測試數據
INSERT INTO `article` VALUES
(1,'{\"id\": 1, \"name\": \"php\"}','[\"php\", \"mysql\", \"linux\", \"nginx\", \"redis\", \"memcache\", \"mongodb\"]'),
(2,'{\"id\": 2, \"name\": \"java\"}','[\"java\", \"mysql\", \"oracel\", \"linux\", \"nginx\", \"redis\", \"memcache\", \"mongodb\"]'),
(3,'{\"id\": \"3\", \"name\": \"c#\"}','[\"c\", \"c++\", \"OS\", \"linux\", \"unix\", \"IBM\"]');總體預覽
待完善
二、json查詢
select id,json_extract(category,'$.name') as name from test.article;#提取json字段裏面的信息
# column->path形式 訪問json中的元素 category->'$.name'
select id,category->'$.name' as name from test.article;#提取json字段裏面的信息(訪問json中的元素 category->'$.name')
select id,json_unquote(json_extract(category,'$.name')) as name from test.article;#提取json字段裏面的信息,json_unqoute去雙引號
select id,category->>'$.name' as name from test.article;
select * from test.article where category='{"id": 1, "name": "php"}'; #json不同於字符串，不能當作字符串做比較
select * from test.article where category=cast('{"id": 1, "name": "php"}' as JSON); #通過CAST將字符串轉換成JSON形式
select * from test.article where category->'$.name'='java';
select * from test.article where category->>'$.name'='java';
#JSON 中的元素搜索是嚴格區分變量類型的，比如說整型和字符串是嚴格區分的
select * from test.article where category->'$.id'='2';#字符號串
select * from test.article where category->'$.id'=2;#整形
select * from test.article where category->'$.id'='3';#字符號串
select * from test.article where json_extract(category,'$.id')='3';#字符號串
select * from test.article where json_contains(category,'2','$.id');#整數
select * from test.article where json_contains(category,'"3"','$.id');#字符號串
select * from test.article where json_contains(tags,'"linux"');#字符號串
2、查詢json格式的字段
mysql> select jsn_extract(data, '.name′),jsnextract(data,′.address') from user;
+-----------------------------+-------------------------------+
| jsn_extract(data, '.name′)|jsnextract(data,′.address') |
+-----------------------------+-------------------------------+
| "David" | "Shangahai" |
| "Amy" | NULL |
+-----------------------------+-------------------------------+
2 rows in set (0.00 sec)
3、給json格式的某個鍵字段創建索引。首先創建虛擬列，之後在改虛擬列上創建索引。
mysql> ALTER TABLE user ADD user_name varchar(128)
-> GENERATED ALWAYS AS (jsn_extract(data,'$.name')) VIRTUAL;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> select user_name from user;
+-----------+
| user_name |
+-----------+
| "Amy" |
| "David" |
+-----------+
2 rows in set (0.00 sec)
mysql> alter table user add index idx_username (user_name);
Query OK, 2 rows affected (0.01 sec)
Records: 2 Duplicates: 0 Warnings: 0
4、之後通過虛擬列名對json特定列進行索引查詢：
mysql> explain select * from user where user_name='"Amy"'\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: user
partitions: NULL
type: ref
possible_keys: idx_username
key: idx_username
key_len: 131
ref: const
rows: 1
filtered: 100.00
Extra: NULL
1 row in set, 1 warning (0.00 sec)
三、json更新
更新 JSON
如果是整個 json 更新的話，和插入時類似的。
mysql> UPDATE lnmp SET tags = '[1, 3, 4]' WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> SELECT * FROM lnmp;
+----+------------------------------+-----------+
| id | category | tags |
+----+------------------------------+-----------+
| 1 | {"id": 1, "name": "lnmp.cn"} | [1, 3, 4] |
| 2 | {"id": 2, "name": "php.net"} | [1, 3, 5] |
+----+------------------------------+-----------+
2 rows in set (0.00 sec)但如果要更新 JSON 下的元素，MySQL 並不支持 column->path 的形式
mysql> UPDATE lnmp SET category->'$.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->'$[0]' = 2 WHERE id = 1' at line 1
則可能要用到以下幾個函數
JSON_INSERT() 插入新值，但不會覆蓋已經存在的值
mysql> UPDATE lnmp SET category = JSON_INSERT(category, '$.name', 'lnmp', '$.url', 'www.lnmp.cn') WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> SELECT * FROM lnmp;
+----+----------------------------------------------------+-----------+
| id | category | tags |
+----+----------------------------------------------------+-----------+
| 1 | {"id": 1, "url": "www.lnmp.cn", "name": "lnmp.cn"} | [1, 3, 4] |
| 2 | {"id": 2, "name": "php.net"} | [1, 3, 5] |
+----+----------------------------------------------------+-----------+
2 rows in set (0.00 sec)可以看到 name 沒有被修改，但新元素 url 已經添加進去
JSON_SET() 插入新值，並覆蓋已經存在的值
mysql> UPDATE lnmp SET category = JSON_SET(category, '$.host', 'www.lnmp.cn', '$.url', 'http://www.lnmp.cn') WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> SELECT * FROM lnmp;
+----+----------------------------------------------------------------------------------+-----------+
| id | category | tags |
+----+----------------------------------------------------------------------------------+-----------+
| 1 | {"id": 1, "url": "http://www.lnmp.cn", "host": "www.lnmp.cn", "name": "lnmp.cn"} | [1, 3, 4] |
| 2 | {"id": 2, "name": "php.net"} | [1, 3, 5] |
+----+----------------------------------------------------------------------------------+-----------+
2 rows in set (0.00 sec)可以看到 host 已經插入，url 已經被修改
JSON_REPLACE() 只替換存在的值
mysql> UPDATE lnmp SET category = JSON_REPLACE(category, '$.name', 'php', '$.url', 'http://www.php.net') WHERE id = 2;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> SELECT * FROM lnmp;
+----+----------------------------------------------------------------------------------+-----------+
| id | category | tags |
+----+----------------------------------------------------------------------------------+-----------+
| 1 | {"id": 1, "url": "http://www.lnmp.cn", "host": "www.lnmp.cn", "name": "lnmp.cn"} | [1, 3, 4] |
| 2 | {"id": 2, "name": "php"} | [1, 3, 5] |
+----+----------------------------------------------------------------------------------+-----------+
2 rows in set (0.00 sec)可以看到 name 已經被替換，url 不存在被忽略。
JSON_REMOVE() 刪除 JSON 元素
mysql> UPDATE lnmp SET category = JSON_REMOVE(category, '$.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)更多函數請參考：http://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html
MySQL JSON 在 PHP 中的表現
雖然在 MySQL 是個JSON 類型，但實際在 PHP 應用中返回的是 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]"
}
}mysql5.7新特性JSON數據類型解析