How to create a json column from multiple columns?

Question

The table which needs to be converted to a json field.

ID,  product, line_item, createdDate

123,  valA,    valB,    '2019-02-02'

The JSON table would be like.

ID,  json_column

123, { valA : 
             {valB : '2019-02-02'}}

Now, I'm not sure what kind of parse_json function can be used to create this column. When I use the column name, it errors out - 'Invalid Identifier'

Query used.

select ID, parse_json( {product : { line_item : createdDate }};

Answer 1

First of all, always try to provide a fully reproducible example

Here's one for your question based on what you wrote

create or replace table x(id int, 
                          product varchar, 
                          line_item varchar, 
                          createdDate varchar) 
as select * from values
    (123,'valA','valB','2019-02-02');

select * from x;
-----+---------+-----------+-------------+
 ID  | PRODUCT | LINE_ITEM | CREATEDDATE |
-----+---------+-----------+-------------+
 123 | valA    | valB      | 2019-02-02  |
-----+---------+-----------+-------------+

Now, to get the result you want you can use the OBJECT_CONSTRUCT function, like this:

select id, object_construct(product, object_construct(line_item, createddate)) from x;
-----+---------------------------------------------------------------------+
 ID  | OBJECT_CONSTRUCT(PRODUCT, OBJECT_CONSTRUCT(LINE_ITEM, CREATEDDATE)) |
-----+---------------------------------------------------------------------+
 123 | {                                                                   |
     |   "valA": {                                                         |
     |     "valB": "2019-02-02"                                            |
     |   }                                                                 |
     | }                                                                   |
-----+---------------------------------------------------------------------+

You might also need OBJECT_AGG if you want to group multiple line items together.