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.
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.
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
+----+----------------------------------------------------------------+
备注:查询到data字段的值是json对象的值.
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????? | +-----------------------------+--------------------------------+
备注:查询出来的就是key,name和address的对应的value.
以上就是土嘎嘎小编为大家整理的mysql中_创建包含json数据类型的表?创建json表时候的注意事项?查询json字段中某个key的值?相关主题介绍,如果您觉得小编更新的文章只要能对粉丝们有用,就是我们最大的鼓励和动力,不要忘记讲本站分享给您身边的朋友哦！！