MySQL5.7 JSON类型使用介绍

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转载：http://blog.csdn.net/yueliangdao0608/article/details/49760213

            &nbsp; &nbsp; 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。<br>&nbsp; &nbsp; 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。<br><br><br>示例表结构：<br><br><div class="dp-highlighter bg_sql"><div class="bar"><div class="tools"><b>[sql]</b> <a href="#" class="ViewSource" title="view plain" onclick="dp.sh.Toolbar.Command('ViewSource',this);return false;">view plain</a><span class="tracking-ad" data-mod="popu_168"> <a href="#" class="CopyToClipboard" title="copy" onclick="dp.sh.Toolbar.Command('CopyToClipboard',this);return false;">copy</a><div style="position: absolute; left: 289px; top: 489px; width: 16px; height: 16px; z-index: 99;"><embed id="ZeroClipboardMovie_1" src="http://static.blog.csdn.net/scripts/ZeroClipboard/ZeroClipboard.swf" loop="false" menu="false" quality="best" bgcolor="#ffffff" name="ZeroClipboardMovie_1" allowscriptaccess="always" allowfullscreen="false" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer" flashvars="id=1&amp;width=16&amp;height=16" wmode="transparent" width="16" height="16" align="middle"></div></span><span class="tracking-ad" data-mod="popu_169"> <a href="#" class="PrintSource" title="print" onclick="dp.sh.Toolbar.Command('PrintSource',this);return false;">print</a></span><a href="#" class="About" title="?" onclick="dp.sh.Toolbar.Command('About',this);return false;">?</a></div></div><ol start="1" class="dp-sql"><li class="alt"><span><span class="keyword">CREATE</span><span>&nbsp;</span><span class="keyword">TABLE</span><span>&nbsp;json_test(&nbsp;&nbsp;</span></span></li><li class=""><span>id&nbsp;<span class="keyword">INT</span><span>,&nbsp;&nbsp;</span></span></li><li class="alt"><span>person_desc&nbsp;TEXT&nbsp;&nbsp;</span></li><li class=""><span>)ENGINE&nbsp;INNODB;&nbsp;&nbsp;</span></li></ol><div class="save_code tracking-ad" data-mod="popu_249" style="display: none;"><a href="javascript:;"><img src="http://static.blog.csdn.net/images/save_snippets.png"></a></div></div><pre name="code" class="sql" style="display: none;">CREATE TABLE json_test(

id INT,
person_desc TEXT
)ENGINE INNODB;

我们来插入一条记录：
I

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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”
}]
}’);

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" 
    }] 
}');

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。

现在到了MySQL5.7，我们重新修改下表结构：

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ALTER TABLE json_test MODIFY person_desc json;

ALTER TABLE json_test MODIFY person_desc json;

先看看插入的这行JSON数据有哪些KEY：

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mysql> SELECT id,json_keys(person_desc) as “keys” FROM json_test\G
***************** 1. row *****************
id: 1
keys: [”authors”, “musicians”, “programmers”]
1 row in set (0.00 sec)

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

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：

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mysql> SELECT json_extract(AUTHORS,‘.lastName[0]') AS 'name', AUTHORS FROM  </li><li class="">    -> (  </li><li class="alt">    -> 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  </li><li class="">    -> UNION ALL  </li><li class="alt">    -> SELECT id,json_extract(person_desc,'.authors[2][0]’) AS “authors” FROM json_test
-> ) AS T1
-> ORDER BY NAME DESC\G
***************** 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)

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 DESC\G 
***************** 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)

现在来把详细的值罗列出来：

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mysql> SELECT
-> json_extract(AUTHORS,’.firstName[0]') AS "firstname",  </li><li class="alt">    -> json_extract(AUTHORS,'.lastName[0]’) AS “lastname”,
-> json_extract(AUTHORS,’.genre[0]') AS "genre"  </li><li class="alt">    -> FROM  </li><li class="">    -> (  </li><li class="alt">    -> SELECT id,json_extract(person_desc,'.authors[0]’) AS “authors” FROM json
_test
-> ) AS T\G
***************** 1. row *****************
firstname: ”Isaac”
lastname: ”Asimov”
genre: ”sciencefiction”
1 row in set (0.00 sec)

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 T\G 
***************** 1. row ***************** 
firstname: "Isaac" 
 lastname: "Asimov" 
    genre: "sciencefiction" 
1 row in set (0.00 sec)

我们进一步来演示把authors 这个KEY对应的所有对象删掉。

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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

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

查找下对应的KEY，发现已经被删除掉了。

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mysql> SELECT json_contains_path(person_desc,‘all’,’.authors') as authors_exist  </li><li class="">s FROM json_test\G  </li><li class="alt">*************************** 1. row ***************************  </li><li class="">authors_exists: 0  </li><li class="alt">1 row in set (0.00 sec)  </li></ol><div class="save_code tracking-ad" data-mod="popu_249" style="display: none;"><a href="javascript:;"><img src="http://static.blog.csdn.net/images/save_snippets.png"></a></div></div><pre name="code" class="sql" style="display: none;">mysql> SELECT json_contains_path(person_desc,'all','.authors’) as authors_exist
s FROM json_test\G
***************** 1. row *****************
authors_exists: 0
1 row in set (0.00 sec)

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。

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