Combination of Oracle and JSON

A lot of people JSON No stranger ,JSON(JavaScript Object Notation) Is a lightweight data exchange format , He was based on ECMAScript(European Computer Manufacturers Association, Developed by the European Computer Association js standard ) A subset of , Use text format completely independent of programming language to store and represent data . A simple and clear hierarchy makes JSON Become the ideal data exchange language . Easy to read and write , At the same time, it is also easy for machine analysis and generation , And effectively improve the network transmission efficiency .

In short ,JSON Is a syntax for storing and exchanging data .JSON The essence is string ,JSON Data is used in language , Whether it's Java、C#, still js, You can use JSON.

JSON Is a set of key value pairs of data objects , stay JavaScript It's inside JavaScript The object of , stay Java The middle is Java Of JSON object ( class /VO).JSON Write the data as the name / It's worth it , name / The value consists of the field name , Followed by a colon and a value , General format , As shown below ,

name={name01：“test1”,name02={ name02：“test2”,name021：“test3”} }

stay JSON in , The value must be one of the following data types ,

• character string

• Numbers
  

• object (JSON object )

• Array
  

• Boolean
  

• Null
  

JSON The value of cannot be one of the following data types ,

• function
  

• date

• undefined

Friends with development experience may have used it before XML As a format for data transmission , Here is a XML Examples of data formats ,

This is the use of JSON Show examples of the same data ,

You can see ,JSON Simple grammar format and clear hierarchy are obviously better than XML Easy to read , And in terms of data exchange , because JSON The characters used are more than XML much less , It can greatly save the bandwidth occupied by data transmission , Transmission efficiency , Will be higher than XML.

Oracle from 12c Support from the beginning JSON Storage and retrieval of , Relevant functions have been enhanced in each version , For example, some JSON The limitation of , The allowed length and other features will be improved , for example 12c Description of ,JSON search index Support 64 byte ,

https://docs.oracle.com/en/database/oracle/oracle-database/12.2/adjsn/oracle-json-restrictions.html#GUID-1DB81125-54A7-4CB6-864B-78E0E7E407C9

19c Description of ,JSON search index Has been able to support 255 byte ,

https://docs.oracle.com/en/database/oracle/oracle-database/19/adjsn/oracle-json-restrictions.html#GUID-1DB81125-54A7-4CB6-864B-78E0E7E407C9

So when we use these features , We need to pay attention to the support differences of different versions .

Oracle We can use json_object() Function to convert the search result into JSON, As shown below ,

You can also customize it key,

You can store the search results as a list ,

It also supports sorting ,

Use only json_object(), Each record is a separate json, If you want to generate one for all records json, Can combine json_arrayagg Together with , As shown below ,

But this error is likely to occur , There are many returned record data , Prompt maximum 4000,

This is because json_arrayagg() There are two types of returns ,varchar2 and clob, If you don't explicitly specify , It's used varchar2, If the limit is exceeded , You can use clob type , More content will be output ,

https://docs.oracle.com/en/database/oracle/oracle-database/19/sqlrf/JSON_ARRAYAGG.html#GUID-6D56077D-78DE-4CC0-9498-225DDC42E054

increase returning clob Clause , You can show ,

and JSON There are many related functions , If you need to know ,

For some basic JSON Operational requirements ,Oracle It can still be satisfied , This avoids going through procedures or SQL Splicing JSON The operation of , In terms of convenience , There is some help .

Reference material ,

https://baike.baidu.com/item/JSON/2462549?fr=aladdin

https://blog.csdn.net/weixin_44600235/article/details/107630279

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