Re: [GENERAL] json select question

[FarjadFarid(ChkNet)]

 

This is probably the start of your quest into this project. No doubt you’ll 
need to handle other queries. 

 

So my suggestion is first to rationalise the data storage before digging any 
deeper. 

 

 

 

From: pgsql-general-ow...@postgresql.org 
[mailto:pgsql-general-ow...@postgresql.org] On Behalf Of CS DBA
Sent: 22 September 2016 00:54
To: pgsql-general <pgsql-general@postgresql.org>
Subject: [GENERAL] json select question

 

All;

 

I'm working with a client running postgres 9.2, they have a table with a 
"json_data_string" column of type json

 

the data looks something like this with lots of rows for each (i.e. lots of 
json_data_string->book_name rows, lots of json_data_string->catalog_name rows, 
etc:

'{ "book_name": "Book the Fourth", "author": { "first_name": "Charles", 
"last_name": "Davis" } }'
'{ "catalog_name": "Catalog the Fourth", "author": { "first_name": "Charles", 
"last_name": "Davis" } }'
'{ "magazine_name": "mag4", "author": { "first_name": "Charles", "last_name": 
"Davis" } }'
'{ "category_name": "region", "author": { "first_name": "Charles", "last_name": 
"Davis" } }'
 
 
How can i pull a unique list of all json column names? such as book_name, 
catalog_name, etc
 
Thanks in advance

Re: [GENERAL] json select question

[John R Pierce]

On 9/21/2016 4:54 PM, CS DBA wrote:

How can i pull a unique list of all json column names? such as book_name, 
catalog_name, etc


try json_object_keys() ... 
https://www.postgresql.org/docs/current/static/functions-json.html


but this will only pull the top level keys, like (from the first row of 
your example) , book_name, author... it won't pull out any second level 
fields like first_name, last_name.


you'll likely need to run this on all rows, and do a group by to get 
what you need.


thats a pretty messy way of storing data, btw, and not very relational, 
having a key name indicate a record type, and tossing all the record 
types into the same table.



--
john r pierce, recycling bits in santa cruz

[GENERAL] json select question

[CS DBA]

All;


I'm working with a client running postgres 9.2, they have a table with a 
"json_data_string" column of type json



the data looks something like this with lots of rows for each (i.e. lots 
of json_data_string->book_name rows, lots of 
json_data_string->catalog_name rows, etc:


|'{ "book_name": "Book the Fourth", "author": { "first_name": "Charles", 
"last_name": "Davis" } }' ||'{ "catalog_name": "Catalog the Fourth", "author": { "first_name": 
"Charles", "last_name": "Davis" } }'|
|'{ "magazine_name": "mag4", "author": { "first_name": "Charles", 
"last_name": "Davis" } }' |||'{ "category_name": "region", "author": { "first_name": "Charles", 
"last_name": "Davis" } }'||



How can i pull a unique list of all json column names? such as book_name, 
catalog_name, etc

Thanks in advance