MySQL中json欄位的操作方法

阿新 • • 發佈：2020-11-10

MySQL5.7.8中引入了json欄位，這種型別的欄位使用的頻率比較低，但是在實際操作中，有些業務仍然在用，我們以此為例，介紹下json欄位的操作方法：

還是從例子看起：

mysql> create table test1(id int,info json);
Query OK,0 rows affected (0.02 sec)

mysql> insert into test1 values (1,'{"name":"yeyz","age":26}'),(2,'{"name":"zhangsan","age":30}'),(3,'{"name":"lisi","age":35}');
Query OK,3 rows affected (0.02 sec)
Records: 3 Duplicates: 0 Warnings: 0

mysql> select * from test1;
+------+---------------------------------+
| id  | info              |
+------+---------------------------------+
|  1 | {"age": 26,"name": "yeyz"}   |
|  2 | {"age": 30,"name": "zhangsan"} |
|  3 | {"age": 35,"name": "lisi"}   |
+------+---------------------------------+
3 rows in set (0.00 sec)

首先我們建立了一個表test1，其中id是int欄位，info是json欄位，插入了三條資料，如上：

mysql> select * from test1 where json_extract(info,"$.age")>=30;
+------+---------------------------------+
| id  | info              |
+------+---------------------------------+
|  2 | {"age": 30,"name": "lisi"}   |
+------+---------------------------------+
2 rows in set (0.00 sec)

我們可以通過json_extract的方法得到json中的內容。其中：

1、$符號代表的是json的根目錄，

2、我們使用$.age相當於取出來了json中的age欄位，

3、當然，在函式最前面，應該寫上欄位名字info

下面來看json中常用的函式：

a、json_valid判斷是否是json欄位，如果是，返回1，如果不是，返回0

mysql> select json_valid(2);
+---------------+
| json_valid(2) |
+---------------+
|       0 |
+---------------+
1 row in set (0.01 sec)
mysql> select json_valid('{"num":2}');
+-------------------------+
| json_valid('{"num":2}') |
+-------------------------+
|            1 |
+-------------------------+
1 row in set (0.00 sec)

mysql> select json_valid('2');
+-----------------+
| json_valid('2') |
+-----------------+
|        1 |
+-----------------+
1 row in set (0.00 sec)
mysql> select json_valid('name');
+--------------------+
| json_valid('name') |
+--------------------+
|         0 |
+--------------------+
1 row in set (0.00 sec)

這裡需要注意的是，如果傳入了字串2，那麼，返回結果是1

b、json_keys傳回執行json欄位最上一層的key值

mysql> select json_keys('{"name":"yeyz","score":100}');
+------------------------------------------+
| json_keys('{"name":"yeyz","score":100}') |
+------------------------------------------+
| ["name","score"]            |
+------------------------------------------+
1 row in set (0.01 sec)
mysql> select json_keys('{"name":"yeyz","score":{"math":100,"English":95}}');
+----------------------------------------------------------------+
| json_keys('{"name":"yeyz","English":95}}') |
+----------------------------------------------------------------+
| ["name","score"]                       |
+----------------------------------------------------------------+
1 row in set (0.00 sec)
#如果有多層，可以在最後面使用$的方法，拿到其中的某一層的目錄
mysql> select json_keys('{"name":"yeyz","English":95}}','$.score');
+--------------------------------------------------------------------------+
| json_keys('{"name":"yeyz",'$.score') |
+--------------------------------------------------------------------------+
| ["math","English"]                           |
+--------------------------------------------------------------------------+
1 row in set (0.00 sec)

c、json_length函式，返回最上一層的key個數，如果想取到中間的某一層，則可以使用$的方法，如下：

mysql> select json_length('{"name":"yeyz","English":95},"age":26}');
+---------------------------------------------------------------------------+
| json_length('{"name":"yeyz","age":26}') |
+---------------------------------------------------------------------------+
|                                     3 |
+---------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> select json_length('{"name":"yeyz","age":26}','$.score');
+-------------------------------------------------------------------------------------+
| json_length('{"name":"yeyz",'$.score') |
+-------------------------------------------------------------------------------------+
|                                          2 |
+-------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

d、json_depth函式，json檔案的深度，測試例子如下：

mysql> select json_depth('{"aaa":1}'),json_depth('{}');
+-------------------------+------------------+
| json_depth('{"aaa":1}') | json_depth('{}') |
+-------------------------+------------------+
|            2 |        1 |
+-------------------------+------------------+
1 row in set (0.00 sec)

mysql> select json_depth('{"name":"yeyz","age":26}');
+--------------------------------------------------------------------------+
| json_depth('{"name":"yeyz","age":26}') |
+--------------------------------------------------------------------------+
|                                    3 |
+--------------------------------------------------------------------------+
1 row in set (0.00 sec)

這裡需要注意的是，形如{'aa':1}這種形式的json，其深度是2

e、json_contains_path函式檢索json中是否有一個或者多個成員。

mysql> set @j='{"a":1,"b":2,"c":{"d":4}}';
Query OK,0 rows affected (0.00 sec)
#one的意思是隻要包含一個成員，就返回1
mysql> select json_contains_path(@j,'one','$.a','$.e');
+------------------------------------------+
| json_contains_path(@j,'$.e') |
+------------------------------------------+
|                    1 |
+------------------------------------------+
1 row in set (0.00 sec)
#all的意思是所有的成員都包含，才返回1
mysql> select json_contains_path(@j,'all','$.e') |
+------------------------------------------+
|                    0 |
+------------------------------------------+
1 row in set (0.01 sec)

mysql> select json_contains_path(@j,'$.c.d');
+--------------------------------------+
| json_contains_path(@j,'$.c.d') |
+--------------------------------------+
|                  1 |
+--------------------------------------+
1 row in set (0.00 sec)

mysql> select json_contains_path(@j,'$.a.d');
+--------------------------------------+
| json_contains_path(@j,'$.a.d') |
+--------------------------------------+
|                  0 |
+--------------------------------------+
1 row in set (0.00 sec)

f、json_type函式，判斷json中的成員的型別，需要和json_extract結合起來使用。

mysql> select * from test1;
+------+---------------------------------+
| id  | info              |
+------+---------------------------------+
|  1 | {"age": 26,"name": "lisi"}   |
+------+---------------------------------+
3 rows in set (0.00 sec)
#判斷name的型別
mysql> select json_type(json_extract(info,"$.name")) from test1;
+----------------------------------------+
| json_type(json_extract(info,"$.name")) |
+----------------------------------------+
| STRING                 |
| STRING                 |
| STRING                 |
+----------------------------------------+
3 rows in set (0.00 sec)
#判斷age的型別
mysql> select json_type(json_extract(info,"$.age")) from test1;
+---------------------------------------+
| json_type(json_extract(info,"$.age")) |
+---------------------------------------+
| INTEGER                |
| INTEGER                |
| INTEGER                |
+---------------------------------------+
3 rows in set (0.00 sec)
#判斷name和age組合起來的型別，可以看到是array
mysql> select json_type(json_extract(info,"$.name","$.age")) from test1;
+------------------------------------------------+
| json_type(json_extract(info,"$.age")) |
+------------------------------------------------+
| ARRAY                     |
| ARRAY                     |
| ARRAY                     |
+------------------------------------------------+
3 rows in set (0.00 sec)

g、*的作用，所有的值,看下面的例子。

{
 "a":1,"c":
   {
    "d":4
   }
 "e":
   {
   "d":
     {
     "ddd":
     "5"
     }
   }
}
mysql> set @j='{"a":1,"c":{"d":4},"e":{"d":{"ddd":"5"}}}';
Query OK,0 rows affected (0.00 sec)
#所有成員
mysql> select json_extract(@j,'$.*');
+---------------------------------------+
| json_extract(@j,'$.*')        |
+---------------------------------------+
| [1,2,{"d": 4},{"d": {"ddd": "5"}}] |
+---------------------------------------+
1 row in set (0.00 sec)
#所有成員中的d成員
mysql> select json_extract(@j,'$.*.d');
+--------------------------+
| json_extract(@j,'$.*.d') |
+--------------------------+
| [4,{"ddd": "5"}]    |
+--------------------------+
1 row in set (0.00 sec)

以上就是MySQL中json欄位的操作方法的詳細內容，更多關於MySQL json欄位的資料請關注我們其它相關文章！