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MySQL + JSON = King fried
2022-07-01 17:43:00 【End code life】
Relational structured storage has some disadvantages , Because it needs to define all columns and their corresponding types in advance . But the business is developing , You may need to extend the description function of a single column , At this time , If you can use it well JSON data type , Then we can get through the boundary between the storage of relational and non relational data , Provide better architecture choices for business .
Of course , Many students are using JSON Various problems will be encountered in data types , One of the most common mistakes is to type JSON Simply understood as string type . But when you finish reading this article , Will really realize JSON The power of data types , So as to better store unstructured data in practical work .
1、JSON data type
JSON（JavaScript Object Notation） It is mainly used for data exchange between Internet application services .MySQL Support RFC 7159 Defined JSON standard , There are mainly JSON object and JSON Array Two types of . The following is JSON object , It is mainly used to store relevant information of pictures ：
{
"Image": {
"Width": 800,
"Height": 600,
"Title": "View from 15th Floor",
"Thumbnail": {
"Url": "http://www.example.com/image/xx9943",
"Height": 125,
"Width": 100
},
"IDs": [116, 943, 234, 38793]
}
}
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You can see from it that , JSON Type can well describe the relevant content of data , For example, the width of this picture 、 Height 、 Title, etc. （ The types used here are integers 、 String type ）.
JSON Object in addition to supporting strings 、 integer 、 The date type ,JSON Embedded fields also support array types , As in the code above IDs Field .
Another kind JSON The data type is array type , Such as ：
[
{
"precision": "zip",
"Latitude": 37.7668,
"Longitude": -122.3959,
"Address": "",
"City": "SAN FRANCISCO",
"State": "CA",
"Zip": "94107",
"Country": "US"
},
{
"precision": "zip",
"Latitude": 37.371991,
"Longitude": -122.026020,
"Address": "",
"City": "SUNNYVALE",
"State": "CA",
"Zip": "94085",
"Country": "US"
}
]
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The above example demonstrates a JSON Array , Among them is 2 individual JSON object .
up to now , Maybe many students will put JSON As a large field string type , On the surface , No mistake. . But essentially ,JSON It's a new type , Has its own storage format , You can also create an index on each corresponding field , Do specific optimization , This cannot be achieved by traditional field strings .JSON Another benefit of types is that there is no need to predefine fields , Fields can be expanded indefinitely . The columns of traditional relational database need to be defined in advance , If you want to expand, you need to execute ALTER TABLE … ADD COLUMN … Such a heavy operation .
It's important to note that ,JSON Type is from MySQL 5.7 Version starts to support features , and 8.0 Version solves the problem of updating JSON Log performance bottleneck . If you want to use it in a production environment JSON data type , Highly recommended MySQL 8.0 edition .
So far , You have to JSON The basic concept of type has been understood , Next , We entered the actual combat link ： How to make good use of JSON type ？
2、 Business table structure design practice
User login design
In the database ,JSON Type is more suitable for storing some less modified 、 Relatively static data , For example, the storage of user login information is as follows ：
DROP TABLE IF EXISTS UserLogin;
CREATE TABLE UserLogin (
userId BIGINT NOT NULL,
loginInfo JSON,
PRIMARY KEY(userId)
);
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Due to the more and more diversified login methods of current business , As the same account supports mobile phones 、 WeChat 、QQ To login , So you can use JSON Type stores login information .
next , Insert the data below ：
SET @a = '
{
"cellphone" : "1",
"wxchat" : " Code the agriculture ",
"77" : "1"
}
';
INSERT INTO UserLogin VALUES (1,@a);
SET @b = '
{
"cellphone" : "1188"
}
';
INSERT INTO UserLogin VALUES (2,@b);
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As you can see from the example above , user 1 There are three ways to log in ： Mobile phone verification code login 、 Wechat login 、QQ Sign in , And users 2 Only the mobile phone verification code can log in .
And if you don't use JSON data type , You need to use the following method to create a table ：
SELECT
userId,
JSON_UNQUOTE(JSON_EXTRACT(loginInfo,"$.cellphone")) cellphone,
JSON_UNQUOTE(JSON_EXTRACT(loginInfo,"$.wxchat")) wxchat
FROM UserLogin;
+--------+-------------+--------------+
| userId | cellphone | wxchat |
+--------+-------------+--------------+
| 1 | 11| Code the agriculture |
| 2 | 11| NULL |
+--------+-------------+--------------+
2 rows in set (0.01 sec)
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Yes, of course , Every time JSON_EXTRACT、JSON_UNQUOTE Very trouble ,MySQL It also provides ->> expression , And above SQL The effect is exactly the same ：
SELECT
userId,
loginInfo->>"$.cellphone" cellphone,
loginInfo->>"$.wxchat" wxchat
FROM UserLogin;
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When JSON Very large amount of data , Users want to know more about JSON When data is effectively retrieved , You can use MySQL Of Function index Functional pair JSON Index a field in .
For example, in the user login example above , Suppose that the user must bind a unique mobile phone number , And hope to use mobile phone number for user retrieval in the future , You can create the following index ：
ALTER TABLE UserLogin ADD COLUMN cellphone VARCHAR(255) AS (loginInfo->>"$.cellphone");
ALTER TABLE UserLogin ADD UNIQUE INDEX idx_cellphone(cellphone);
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Above SQL First, create a virtual column cellphone, This column is made up of functions loginInfo->>"$.cellphone" Calculated . Then create a unique index on this virtual column idx_cellphone. At this time, through the virtual column cellphone The query , You can see that the optimizer will use the newly created idx_cellphone Indexes ：
EXPLAIN SELECT * FROM UserLogin
WHERE cellphone = '11'\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: UserLogin
partitions: NULL
type: const
possible_keys: idx_cellphone
key: idx_cellphone
key_len: 1023
ref: const
rows: 1
filtered: 100.00
Extra: NULL
1 row in set, 1 warning (0.00 sec)
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Of course , We can start by creating tables , Complete the creation of virtual columns and functional indexes . The columns created in the following table cellphone The corresponding is JSON The content in , It's a virtual column ;uk_idx_cellphone Is in the virtual column cellphone Index created on .
CREATE TABLE UserLogin (
userId BIGINT,
loginInfo JSON,
cellphone VARCHAR(255) AS (loginInfo->>"$.cellphone"),
PRIMARY KEY(userId),
UNIQUE KEY uk_idx_cellphone(cellphone)
);
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User portrait design
Some businesses need user portraits （ That is to label users ）, Then according to the user's label , Through data mining technology , Make corresponding product recommendations . such as ：
- In the e-commerce industry , According to the user's dressing preferences , Recommend corresponding products ;
- In the music industry , According to the music style users like and the singers they often listen to , Recommend the corresponding song ;
- In the financial industry , According to the user's risk preference and investment experience , Recommend corresponding financial products .
Here , I strongly recommend that you use JSON Type stores user portrait information in the database , And combine JSON The characteristics of array type and multivalued index are used for efficient query . Suppose there is a picture definition table ：
CREATE TABLE Tags (
tagId bigint auto_increment,
tagName varchar(255) NOT NULL,
primary key(tagId)
);
SELECT * FROM Tags;
+-------+--------------+
| tagId | tagName |
+-------+--------------+
| 1 | 70 after |
| 2 | 80 after |
| 3 | 90 after |
| 4 | 00 after |
| 5 | Love sports |
| 6 | Highly educated |
| 7 | Small endowment |
| 8 | A house |
| 9 | A car |
| 10 | I often go to the cinema |
| 11 | Love online shopping |
| 12 | Love takeout |
+-------+--------------+
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You can see , surface Tags It's a picture definition table , Used to describe how many tags are currently defined , Then label each user , Such as user David, His label is 80 after 、 Highly educated 、 Small endowment 、 A house 、 I often go to the cinema ; user Tom,90 after 、 I often go to the cinema 、 Love takeout .
If not JSON Data type for label storage , The user tag is usually passed through a string , How to add a delimiter , Access all user tags in one field ：
+-------+---------------------------------------+
| user | label |
+-------+---------------------------------------+
|David |80 after ; Highly educated ; Small endowment ; A house ; I often go to the cinema |
|Tom |90 after ; I often go to the cinema ; Love takeout |
+-------+---------------------------------------
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The disadvantage of doing so is ： Users who are not good at searching for specific portraits , In addition, the separator is also a self convention , In fact, other data can be stored arbitrarily in the database , Finally, dirty data is generated .
use JSON Data type can solve this problem well ：
DROP TABLE IF EXISTS UserTag;
CREATE TABLE UserTag (
userId bigint NOT NULL,
userTags JSON,
PRIMARY KEY (userId)
);
INSERT INTO UserTag VALUES (1,'[2,6,8,10]');
INSERT INTO UserTag VALUES (2,'[3,10,12]');
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among ,userTags The stored tag is the table Tags Those tag values that have been defined , Just use JSON Array type for storage .
MySQL 8.0.17 Version starting support Multi-Valued Indexes, Used in JSON Create index on array , And through the function member of、json_contains、json_overlaps To quickly retrieve index data . So you can watch UserTag To create a Multi-Valued Indexes：
ALTER TABLE UserTag
ADD INDEX idx_user_tags ((cast((userTags->"$") as unsigned array)));
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If you want to query the user portrait, it is a user who often watches movies , You can use functions MEMBER OF：
EXPLAIN SELECT * FROM UserTag
WHERE 10 MEMBER OF(userTags->"$")\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: UserTag
partitions: NULL
type: ref
possible_keys: idx_user_tags
key: idx_user_tags
key_len: 9
ref: const
rows: 1
filtered: 100.00
Extra: Using where
1 row in set, 1 warning (0.00 sec)
SELECT * FROM UserTag
WHERE 10 MEMBER OF(userTags->"$");
+--------+---------------+
| userId | userTags |
+--------+---------------+
| 1 | [2, 6, 8, 10] |
| 2 | [3, 10, 12] |
+--------+---------------+
2 rows in set (0.00 sec)
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If you want to query the portrait 80 after , Users who often watch movies , You can use functions
JSON_CONTAINS：
EXPLAIN SELECT * FROM UserTag
WHERE JSON_CONTAINS(userTags->"$", '[2,10]')\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: UserTag
partitions: NULL
type: range
possible_keys: idx_user_tags
key: idx_user_tags
key_len: 9
ref: NULL
rows: 3
filtered: 100.00
Extra: Using where
1 row in set, 1 warning (0.00 sec)
SELECT * FROM UserTag
WHERE JSON_CONTAINS(userTags->"$", '[2,10]');
+--------+---------------+
| userId | userTags |
+--------+---------------+
| 1 | [2, 6, 8, 10] |
+--------+---------------+
1 row in set (0.00 sec)
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If you want to query the portrait 80 after 、90 after , Users who often watch movies , You can use the function
JSON_OVERLAP：
EXPLAIN SELECT * FROM UserTag
WHERE JSON_OVERLAPS(userTags->"$", '[2,3,10]')\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: UserTag
partitions: NULL
type: range
possible_keys: idx_user_tags
key: idx_user_tags
key_len: 9
ref: NULL
rows: 4
filtered: 100.00
Extra: Using where
1 row in set, 1 warning (0.00 sec)
SELECT * FROM UserTag
WHERE JSON_OVERLAPS(userTags->"$", '[2,3,10]');
+--------+---------------+
| userId | userTags |
+--------+---------------+
| 1 | [2, 6, 8, 10] |
| 2 | [3, 10, 12] |
+--------+---------------+
2 rows in set (0.01 sec)
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JSON The type is MySQL 5.7 New data type in version , The use of good JSON Data type can effectively solve many practical problems in business . Last , Let me summarize today's highlights ：
Use JSON data type , Recommend to use MySQL 8.0.17 Version above , Better performance , It also supports Multi-Valued Indexes
JSON The advantage of data types is that there is no need to define columns in advance , The data itself is well descriptive ;
Don't use data with obvious relationship JSON Storage , Such as user balance 、 User name 、 User ID card, etc , These are the data that every user must include ;
JSON The data type is recommended for static data storage that is not updated frequently .
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