HANA DB 中 json_object 的等效函数

Question

I would like to return the query results into json format in HANA DB.

There is a json_object function in oracle to achieve this requirement, but I am not seeing any function in HANA. Does anyone knows if this kind of function exists in HANA For example:

Table Author contains non-json data as follows:

---------------------------------------------
|  firstName        |   lastName            |
---------------------------------------------
|  Paulo            |   Coelho              |
|  George           |   Orwell              |
---------------------------------------------

write a select statement to return result as json. In Oracle it can be returned using query:

SELECT json_object(
  KEY 'firstName' VALUE author.first_name, 
  KEY 'lastName'  VALUE author.last_name
)
FROM author

Output looks like this:

---------------------------------------------
| json_array                                 |
---------------------------------------------
| {"firstName":"Paulo","lastName":"Coelho"}  | 
| {"firstName":"George","lastName":"Orwell"} |
----------------------------------------------

Does anyone knows query or function in HANA to achieve the same result?

Answer 1

you can use the already mentioned function in SAP HANA too

JSON_QUERY (
 <JSON_API_common_syntax>
 [ <JSON_output_clause> ]
 [ <JSON_query_wrapper_behavior> ]
 [ <JSON_query_empty_behavior> ON EMPTY ]
 [ <JSON_query_error_behavior> ON ERROR ]
  )

research

Answer 2

For 2.0 SP04 and above there's a for json addition to the select statement . As documentation says, it is only permitted in subqueries, so you need to select individual columns in subselect (if you need a result set of JSON objects) of generate a JSON array as a single scalar result. Column names are inherited from subquery aliases.

Case 1:

with a as (
  select 'AAA' as field1, 'Value 1' as val from dummy union all
  select 'BBB' as field1, 'Value 2' as val from dummy
)
select
  /*Use correlated subquery with single row*/
  json_value((select a.field1, a.val from dummy for json), '$[0]') as res
from a

Or more effort to type-in, but less structure-dependent:

with a as (
  select 'AAA' as field1, 'Value 1' as val from dummy union all
  select 'BBB' as field1, 'Value 2' as val from dummy
)
, json_source as (
  /*Intermediate query to use as correlation source in JSON_TABLE*/
  select (select * from a for json) as tmp_json
  from dummy
)
select json_parsed.*
from json_source,
  json_table(
  json_source.tmp_json
  /*Access individual items*/
  , '$[*]'
  columns (
    res nvarchar(1000) format json path '$'
  )
) as json_parsed

Both return:

RES
{"FIELD1":"AAA","VAL":"Value 1"}
{"FIELD1":"BBB","VAL":"Value 2"}

Or as a scalar query returning JSON array (Case 2):

with a as (
  select 'AAA' as field1, 'Value 1' as val from dummy union all
  select 'BBB' as field1, 'Value 2' as val from dummy
)
select *
from (select * from a for json)

JSONRESULT
[{"FIELD1":"AAA","VAL":"Value 1"},{"FIELD1":"BBB","VAL":"Value 2"}]

Answer 3

That's great to retrieve JSON data from SAP HANA queries.

I was wondering if there is a similar solution for a table header + items structure:

HEADER:
--------------------------------------
|  ID        |   Name                |
--------------------------------------
|  1         |   Coelho              |
|  2         |   Orwell              |
--------------------------------------

ITEMS:
---------------------------------------------------
|  ID        |   LineID         |   Quantity      |
---------------------------------------------------
|  1         |   1              |   4             |
|  1         |   2              |   3             |
|  2         |   1              |   5             |
---------------------------------------------------

---------------------------------------------------
| OUTPUT (single data row)                        |
---------------------------------------------------
[{"ID": 1, "Name": "Coelho", "Items": [{ "LineID": 1, "Quantity": 4}, { "LineID": 2, "Quantity": 3}]}, {"ID": 2, "Name": "Orwell", "Items": [{ "LineID": 1, "Quantity": 5}]}]  
---------------------------------------------------

I know I can write a SQLScript to achieve same results but is not so simple...

Any suggestion?