mysql中json_extract函数的使用?作用是什么?

http://www.cnblogs.com/chuanzhang053/p/9139624.html

需求描述:

　　今天看mysql中的json数据类型,涉及到一些使用,使用到了函数json_extract来

　　获取json字段中某个key的值,在此记录下.

操作过程:

|  2 | {"Tel": "13390989765", "name": "Mike", "address": "Guangzhou"} |
+----+----------------------------------------------------------------+
2 rows in set (0.00 sec)

备注:data字段就是json的数据类型,由键值对组成.

备注:这个查询时直接对json对象进行操作.

3.对tab_json表使用json_extract函数

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;  #如果查询没有的key,那么是可以查询,不过返回的是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)

备注:通过json_extract函数,获取到了json对象的特定key的值.