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Convert a cursor into JSON?

Mike KutzApr 15 2022

Database: 21c ATP Free Tier
I'm looking for the JSON version of this (LiveSQL PL/SQL code for converting cursor to XML)
So, if I give a cursor like:

open cur for
    select column_name, data_type
    from user_tab_cols
    where table_name = 'EMP';

The function should return JSON (or json_object_t) that matches something like:

{ "ROWSET":[
        { "COLUMN_NAME":"EMPNO", "DATA_TYPE":"NUMBER" },
        { "COLUMN_NAME":"DEPTNO", "DATA_TYPE":"NUMBER" },
        { "COLUMN_NAME":"HIRE_DATE", "DATA_TYPE":"DATE" },
        ...
    ]
}

Thanks,
MK
This post has been answered by Stew Ashton on Apr 16 2022
Jump to Answer

Comments

mathguy

It seems to me that you want something like I show below. I am creating a JSON document from a random table (I chose one with a small number of columns, and I limited the row count to 4 to keep the output to a manageable size). The key name ROWSET is hardcoded, but the rest is automatic. Note the use of the wildcard * to stand for "all columns". This can also be used on a view rather than on a table. How you use it on a "cursor" (assuming you need one) I will let you figure out.
Check the documentation for the specific way in which Oracle converts data types from SQL to JSON.
Tested on Oracle 19 on LiveSQL.oracle.com; I only have 12.2 on my machine (on which this obviously fails).

select json_object(key 'ROWSET' value json_arrayagg(json_object(t.*))) as json_str
from   hr.countries t
where  rownum <= 4
;


JSON_STR
---------------------------------
{
"ROWSET" : [
{
"COUNTRY_ID" : "AR",
"COUNTRY_NAME" : "Argentina",
"REGION_ID" : 2
},
{
"COUNTRY_ID" : "AU",
"COUNTRY_NAME" : "Australia",
"REGION_ID" : 3
},
{
"COUNTRY_ID" : "BE",
"COUNTRY_NAME" : "Belgium",
"REGION_ID" : 1
},
{
"COUNTRY_ID" : "BR",
"COUNTRY_NAME" : "Brazil",
"REGION_ID" : 2
}
]
}
1 person found this helpful
Stew Ashton

I don't understand the question. The LiveSQL example produces output with data, whereas you seem to be asking for output that describes the columns. Which is it?

Stew Ashton
Answer

A similar question was asked here:
Is it possible to use JSON SQL functions on a weak ref cursor rather than a table - Ask TOM (0 Bytes)There were two answers:

  1. APEX_JSON
  2. Use native JSON support in Oracle SQL, which requires changing the REF CURSOR itself, or else replacing the REF CURSOR by a named subquery and using a SQL table macro.
    Another approach would be to roll your own generic function: convert the REF CURSOR to a DBMS_SQL cursor, then generate whatever JSON you want.
Marked as Answer by Mike Kutz · Apr 16 2022
1 person found this helpful
Mike Kutz

It looks like APEX_JSON is the tool I'm looking for.
Thanks to both of you.

Mike Kutz

Oh ... Interesting find:
The APEX_JSON trick works on LONG data types (read Data Dictionary)

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Added on Apr 15 2022
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