MySQL 5.7 新特性 JSON 的建立,插入,查詢,更新
從 MySQL 5.7.8 開始,MySQL 支援原生的 JSON 資料型別。
建立 JSON
類似 varchar,設定 JSON 主要將欄位的 type 是 json, 不能設定長度,可以是 NULL 但不能有預設值。
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)</pre>
這樣 JSON 的欄位就建立好了。
插入 JSON
就是插入 json 格式的字串,可以是物件的形式,也可以是陣列的形式
mysql> INSERT INTO `lnmp` (category, tags) VALUES ('{"id": 1, "name": "lnmp.cn"}', '[1, 2, 3]');
Query OK, 1 row affected (0.01 sec)
MySQL 也有專門的函式 JSON_OBJECT,JSON_ARRAY 生成 json 格式的資料
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)
檢視插入的資料
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)</pre>
查詢 JSON
查詢 json 中的資料用 *column->path *的形式,其中物件型別 path 這樣表示 [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)</pre>
可以看到對應字串型別的 category->’$.name’ 中還包含著雙引號,這其實並不是想要的結果,可以用 JSON_UNQUOTE 函式將雙引號去掉,從 MySQL 5.7.13 起也可以通過這個操作符 *->> *這個和 JSON_UNQUOTE 是等價的
mysql> SELECT id, category->'$.name', JSON_UNQUOTE(category->'$.name'), category->>'$.name' FROM lnmp;
+----+--------------------+----------------------------------+---------------------+
| id | category->'$.name' | JSON_UNQUOTE(category-'$.name') | category->>'$.name' |
+----+--------------------+----------------------------------+---------------------+
| 1 | "lnmp.cn" | lnmp.cn | lnmp.cn |
| 2 | "php.net" | php.net | php.net |
+----+--------------------+----------------------------------+---------------------+
2 rows in set (0.00 sec)</pre>
下面說下 JSON 作為條件進行搜尋。因為 JSON 不同於字串,所以如果用字串和 JSON 欄位比較,是不會相等的
mysql> SELECT * FROM lnmp WHERE category = '{"id": 1, "name": "lnmp.cn"}';
Empty set (0.00 sec)
這時可以通過 CAST 將字串轉成 JSON 的形式
mysql> SELECT * FROM lnmp WHERE category = CAST('{"id": 1, "name": "lnmp.cn"}' as JSON);
+----+------------------------------+-----------+
| id | category | tags |
+----+------------------------------+-----------+
| 1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
+----+------------------------------+-----------+
1 row in set (0.00 sec)</pre>
通過 JSON 中的元素進行查詢, 物件型的查詢同樣可以通過 column->path
mysql> SELECT * FROM lnmp WHERE category->'$.name' = 'lnmp.cn';
+----+------------------------------+-----------+
| id | category | tags |
+----+------------------------------+-----------+
| 1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
+----+------------------------------+-----------+
1 row in set (0.00 sec)</pre>
上面有提到 *column->path *形式從 select 中查詢出來的字串是包含雙引號的,但作為條件這裡其實沒什麼影響,-> 和 ->> 結果是一樣的
mysql> SELECT * FROM lnmp WHERE category->>'$.name' = 'lnmp.cn';
+----+------------------------------+-----------+
| id | category | tags |
+----+------------------------------+-----------+
| 1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
+----+------------------------------+-----------+
1 row in set (0.00 sec)
要特別注意的是,JSON 中的元素搜尋是嚴格區分變數型別的,比如說整型和字串是嚴格區分的
mysql> SELECT * FROM lnmp WHERE category->'$.id' = '1';
Empty set (0.00 sec)
mysql> SELECT * FROM lnmp WHERE category->'$.id' = 1;
+----+------------------------------+-----------+
| id | category | tags |
+----+------------------------------+-----------+
| 1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
+----+------------------------------+-----------+
1 row in set (0.00 sec)</pre>
可以看到搜尋字串 1 和整型 1 的結果是不一樣的。
除了用 *column->path *的形式搜尋,還可以用JSON_CONTAINS 函式,但和 *column->path *的形式有點相反的是,JSON_CONTAINS 第二個引數是不接受整數的,無論 json 元素是整型還是字串,否則會出現這個錯誤
mysql> SELECT * FROM lnmp WHERE JSON_CONTAINS(category, 1, '$.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.
這裡必須是要字串 1
mysql> SELECT * FROM lnmp WHERE JSON_CONTAINS(category, '1', '$.id');
+----+------------------------------+-----------+
| id | category | tags |
+----+------------------------------+-----------+
| 1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
+----+------------------------------+-----------+
1 row in set (0.01 sec)
對於陣列型別的 JSON 的查詢,比如說 tags 中包含有 2 的資料,同樣要用 JSON_CONTAINS 函式,同樣第二個引數也需要是字串
mysql> SELECT * FROM lnmp WHERE JSON_CONTAINS(tags, '2');
+----+------------------------------+-----------+
| id | category | tags |
+----+------------------------------+-----------+
| 1 | {"id": 1, "name": "lnmp.cn"} | [1, 2, 3] |
+----+------------------------------+-----------+
1 row in set (0.00 sec)</pre>
更新 JSON
如果是整個 json 更新的話,和插入時類似的。
mysql> UPDATE lnmp SET tags = '[1, 3, 4]' WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> SELECT * FROM lnmp;
+----+------------------------------+-----------+
| id | category | tags |
+----+------------------------------+-----------+
| 1 | {"id": 1, "name": "lnmp.cn"} | [1, 3, 4] |
| 2 | {"id": 2, "name": "php.net"} | [1, 3, 5] |
+----+------------------------------+-----------+
2 rows in set (0.00 sec)
但如果要更新 JSON 下的元素,MySQL 並不支援 *column->path *的形式
mysql> UPDATE lnmp SET category->'$.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->'$[0]' = 2 WHERE id = 1' at line 1
則可能要用到以下幾個函式
JSON_INSERT() 插入新值,但不會覆蓋已經存在的值
mysql> UPDATE lnmp SET category = JSON_INSERT(category, '$.name', 'lnmp', '$.url', 'www.lnmp.cn') WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> SELECT * FROM lnmp;
+----+----------------------------------------------------+-----------+
| id | category | tags |
+----+----------------------------------------------------+-----------+
| 1 | {"id": 1, "url": "www.lnmp.cn", "name": "lnmp.cn"} | [1, 3, 4] |
| 2 | {"id": 2, "name": "php.net"} | [1, 3, 5] |
+----+----------------------------------------------------+-----------+
2 rows in set (0.00 sec)</pre>
可以看到 name 沒有被修改,但新元素 url 已經新增進去
JSON_SET() 插入新值,並覆蓋已經存在的值
mysql> UPDATE lnmp SET category = JSON_SET(category, '$.host', 'www.lnmp.cn', '$.url', 'http://www.lnmp.cn') WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> SELECT * FROM lnmp;
+----+----------------------------------------------------------------------------------+-----------+
| id | category | tags |
+----+----------------------------------------------------------------------------------+-----------+
| 1 | {"id": 1, "url": "http://www.lnmp.cn", "host": "www.lnmp.cn", "name": "lnmp.cn"} | [1, 3, 4] |
| 2 | {"id": 2, "name": "php.net"} | [1, 3, 5] |
+----+----------------------------------------------------------------------------------+-----------+
2 rows in set (0.00 sec)</pre>
可以看到 host 已經插入,url 已經被修改
JSON_REPLACE() 只替換存在的值
mysql> UPDATE lnmp SET category = JSON_REPLACE(category, '$.name', 'php', '$.url', 'http://www.php.net') WHERE id = 2;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> SELECT * FROM lnmp;
+----+----------------------------------------------------------------------------------+-----------+
| id | category | tags |
+----+----------------------------------------------------------------------------------+-----------+
| 1 | {"id": 1, "url": "http://www.lnmp.cn", "host": "www.lnmp.cn", "name": "lnmp.cn"} | [1, 3, 4] |
| 2 | {"id": 2, "name": "php"} | [1, 3, 5] |
+----+----------------------------------------------------------------------------------+-----------+
2 rows in set (0.00 sec)</pre>
可以看到 name 已經被替換,url 不存在被忽略。
JSON_REMOVE() 刪除 JSON 元素
mysql> UPDATE lnmp SET category = JSON_REMOVE(category, '$.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)</pre>
MySQL JSON 在 PHP 中的表現
雖然在 MySQL 是個JSON 型別,但實際在 PHP 應用中返回的是 JSON 格式的字串
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]"
}
}