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来自 计算机教程 2020-04-18 04:08 的文章
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MySQL5.7 JSON类型使用详解

我们进一步来演示把authors 这个KEY对应的所有对象删掉。

JSON的格式非常简单:名称/键值。之前MySQL版本里面要实现这样的存储,要么用VARCHAR要么用TEXT大文本。 MySQL5.7发布后,专门设计了JSON数据类型以及关于这种类型的检索以及其他函数解析。 我们先看看MySQL老版本的JSON存取。

ALTER TABLE json_test MODIFY person_desc json; 

总结

NSERT INTO json_test VALUES (1,'{ "programmers": [{ "firstName": "Brett", "lastName": "McLaughlin", "email": "aaaa" }, { "firstName": "Jason", "lastName": "Hunter", "email": "bbbb" }, { "firstName": "Elliotte", "lastName": "Harold", "email": "cccc" }], "authors": [{ "firstName": "Isaac", "lastName": "Asimov", "genre": "sciencefiction" }, { "firstName": "Tad", "lastName": "Williams", "genre": "fantasy" }, { "firstName": "Frank", "lastName": "Peretti", "genre": "christianfiction" }], "musicians": [{ "firstName": "Eric", "lastName": "Clapton", "instrument": "guitar" }, { "firstName": "Sergei", "lastName": "Rachmaninoff", "instrument": "piano" }] }'); 
mysql SELECT json_contains_path(person_desc,'all','$.authors') as authors_exist s FROM json_testG *************************** 1. row *************************** authors_exists: 0 row in set (0.00 sec) 

现在到了MySQL5.7,我们重新修改下表结构:

查找下对应的KEY,发现已经被删除掉了。

先看看插入的这行JSON数据有哪些KEY:

以上所述是小编给大家介绍的MySQL5.7 JSON类型使用详解,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。在此也非常感谢大家对脚本之家网站的支持!

mysql SELECT id,json_keys(person_desc) as "keys" FROM json_testG *************************** 1. row *************************** id: 1 keys: ["authors", "musicians", "programmers"] row in set (0.00 sec) 

现在来把详细的值罗列出来:

总结下, 虽然MySQL5.7 开始支持JSON数据类型,但是我建议如果要使用的话,最好是把这样的值取出来,然后在应用程序段来计算,毕竟数据库是用来处理简单数据的。

我们可以看到,里面有三个KEY,分别为authors,musicians,programmers。那现在找一个KEY把对应的值拿出来:

我们来插入一条记录:

示例表结构:

mysql SELECT json_extract(AUTHORS,'$.lastName[0]') AS 'name', AUTHORS FROM - ( - SELECT id,json_extract(person_desc,'$.authors[0][0]') AS "authors" FROM json_test - UNION ALL - SELECT id,json_extract(person_desc,'$.authors[1][0]') AS "authors" FROM json_test - UNION ALL - SELECT id,json_extract(person_desc,'$.authors[2][0]') AS "authors" FROM json_test - ) AS T1 - ORDER BY NAME DESCG *************************** 1. row *************************** name: "Williams" AUTHORS: {"genre": "fantasy", "lastName": "Williams", "firstName": "Tad"} *************************** 2. row *************************** name: "Peretti" AUTHORS: {"genre": "christianfiction", "lastName": "Peretti", "firstName": "Frank"} *************************** 3. row *************************** name: "Asimov" AUTHORS: {"genre": "sciencefiction", "lastName": "Asimov", "firstName": "Isaac"} 3 rows in set (0.00 sec) 

那一般我们遇到这样来存储JSON格式的话,只能把这条记录取出来交个应用程序,有应用程序来解析。

mysql UPDATE json_test - SET person_desc = json_remove(person_desc,'$.authors')G Query OK, 1 row affected (0.01 sec) Rows matched: 1 Changed: 1 Warnings: 0 
CREATE TABLE json_test( id INT, person_desc TEXT )ENGINE INNODB; 
mysql SELECT - json_extract(AUTHORS,'$.firstName[0]') AS "firstname", - json_extract(AUTHORS,'$.lastName[0]') AS "lastname", - json_extract(AUTHORS,'$.genre[0]') AS "genre" - FROM - ( - SELECT id,json_extract(person_desc,'$.authors[0]') AS "authors" FROM json _test - ) AS TG *************************** 1. row *************************** firstname: "Isaac" lastname: "Asimov" genre: "sciencefiction" row in set (0.00 sec) 

JSON是一种轻量级的数据交换格式,采用了独立于语言的文本格式,类似XML,但是比XML简单,易读并且易编写。对机器来说易于解析和生成,并且会减少网络带宽的传输。

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