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需求描述:

　　在mysql数据库中,创建包含json数据类型的表.记录下,在创建的过程中,需要注意的问题.

操作过程:

1.通过以下的语句,创建包含json数据类型的表

mysql> create table tab_json(id bigint not null auto_increment,data json,primary key(id));
Query OK, 0 rows affected (0.09 sec)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)

创建json数据类型的表,json字段不能包含默认值:

mysql> create table tab_json_01(id bigint not null auto_increment,data json default '{"name":"Dear"}',primary key(id));
ERROR 1101 (42000): BLOB, TEXT, GEOMETRY or JSON column 'data' can't have a default value

备注:json数据类型的列不能有默认值.

2.向json数据类型中插入数据

mysql> insert into tab_json values (null,'{"name":"david","address":"Beijing","Tel":"132223232444"}');
Query OK, 1 row affected (0.08 sec)mysql> insert into tab_json values (null,'{"name":"Mike","address":"Guangzhou","Tel":"13390989765"}');
Query OK, 1 row affected (0.01 sec)
mysql> insert into tab_json values (null,'Jack');
ERROR 3140 (22032): Invalid JSON text: "Invalid value." at position 0 in value for column 'tab_json.data'

mysql> insert into tab_json values (null,'{"names":"Smith","names":"Nancy"}');  #插入的时候有多个names这个key
Query OK, 1 row affected (0.00 sec)

备注:auto_increment字段通过插入null值,就能实现值的自动增长.json数据类型的类有自动检查插入的值是否是json类型的,如果插入的是json类型以外的,就会报错,也就是说,必须要插入json类型的值.

3.查询json表中的内容

mysql> select * from tab_json;
+----+----------------------------------------------------------------+
| id | data                                                           |
+----+----------------------------------------------------------------+
|  1 | {"Tel": "132223232444", "name": "david", "address": "Beijing"} |
|  2 | {"Tel": "13390989765", "name": "Mike", "address": "Guangzhou"} |
|  3 | {"names": "Smith"}                                             |  #在向json列插入值的时候同样执行标准化,即会将重复的key只保留第一个,即多个names的时候,也只是第一个被保留
+----+----------------------------------------------------------------+
3 rows in set (0.00 sec)

备注:查询到data字段的值是json对象的值.

4.获取json数据类型中某个字段的值

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"                    |
| NULL                        | NULL                           |
+-----------------------------+--------------------------------+
3 rows in set (0.00 sec)

备注:查询出来的就是key,name和address的对应的value.

 

文档创建:2018年6月5日14:07:57

文档更新-1:增加插入数据标准化的内容,标准化指的是,插入的时候,多个重复的key只保留第一个  -- 2018年6月6日16:57:54