需求描述:

今天看mysql中的json數據類型,涉及到一些使用,使用到了函數json_extract來

獲取json字段中某個key的值,在此記錄下.

操作過程:

1.查看包含json字段的表信息

mysql> desc tab_json;

+-------+------------+------+-----+---------+----------------+

| Field | Type?????? | Null | Key | Default | Extra????????? |

+-------+------------+------+-----+---------+----------------+

| id??? | bigint(20) | NO?? | PRI | NULL??? | auto_increment |

| data? | json?????? | YES? |???? | NULL??? |??????????????? |

+-------+------------+------+-----+---------+----------------+

2 rows in set (0.00 sec)

mysql> show create table tab_json;

+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

| Table??? | Create Table??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? |

+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

| tab_json | CREATE TABLE `tab_json` (

`id` bigint(20) NOT NULL AUTO_INCREMENT,

`data` json DEFAULT NULL,

PRIMARY KEY (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8 |

+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

1 row in set (0.00 sec)

mysql> select * from tab_json;

+----+----------------------------------------------------------------+

| id | data?????????????????????????????????????????????????????????? |

+----+----------------------------------------------------------------+

|? 1 | {"Tel": "132223232444", "name": "david", "address": "Beijing"} |

|? 2 | {"Tel": "13390989765", "name": "Mike", "address": "Guangzhou"} |

+----+----------------------------------------------------------------+

2 rows in set (0.00 sec)

備注:data字段就是json的數據類型,由鍵值對組成.

2.json_extract函數的使用

mysql> select json_extract('{"name":"Zhaim","tel":"13240133388"}',"$.tel");

+--------------------------------------------------------------+

| json_extract('{"name":"Zhaim","tel":"13240133388"}',"$.tel") |

+--------------------------------------------------------------+

| "13240133388" |

+--------------------------------------------------------------+

1 row in set (0.00 sec)

mysql> select json_extract('{"name":"Zhaim","tel":"13240133388"}',"$.name");

+---------------------------------------------------------------+

| json_extract('{"name":"Zhaim","tel":"13240133388"}',"$.name") |

+---------------------------------------------------------------+

| "Zhaim" |

+---------------------------------------------------------------+

1 row in set (0.00 sec)

備注:這個查詢時直接對json對象進行操作.

3.對tab_json表使用json_extract函數

mysql> select json_extract(data,'$.name') from tab_json;

+-----------------------------+

| json_extract(data,'$.name') |

+-----------------------------+

| "david" |

| "Mike" |

+-----------------------------+

2 rows in set (0.00 sec)

mysql> select json_extract(data,'$.name'),json_extract(data,'$.tel') from tab_json; #如果查詢沒有的key,那么是可以查詢,不過返回的是NULL.

+-----------------------------+----------------------------+

| json_extract(data,'$.name') | json_extract(data,'$.tel') |

+-----------------------------+----------------------------+

| "david" | NULL |

| "Mike" | NULL |

+-----------------------------+----------------------------+

2 rows in set (0.00 sec)

mysql> select json_extract(data,'$.name'),json_extract(data,'$.address') from tab_json;

+-----------------------------+--------------------------------+

| json_extract(data,'$.name') | json_extract(data,'$.address') |

+-----------------------------+--------------------------------+

| "david" | "Beijing" |

| "Mike" | "Guangzhou" |

+-----------------------------+--------------------------------+

2 rows in set (0.00 sec)

備注:通過json_extract函數,獲取到了json對象的特定key的值.

文檔創建時間:2018年6月5日14:25:41

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