Oracle: JSON object members inside CASE expression? - json

Question

I'm trying to assemble a JSON document with mixed types like [["array"],{"data":"object"},"string"] from a conditional expression.
If I put only JSON types inside, Oracle somehow surmises that I'm composing them inside the outer document:
with t as (
select 'array' data from dual union ALL
select 'object' from dual union all
select 'string' from dual
)
select json_arrayagg(
case data
when 'array' then json_array(data)
when 'object' then json_object('key' value data)
end json
)
from t
/
JSON
------------------------------------------------
[["array"],{"data":"object"}]
As soon as I add a string to the mix, the results of the CASE expression are all treated as strings and encoded accordingly:
with t as (
select 'array' data from dual union ALL
select 'object' from dual union all
select 'string' from dual
)
select json_arrayagg(
case data
when 'array' then json_array(data)
when 'object' then json_object('key' value data)
else data
end
)
from t
/
JSON
------------------------------------------------
["[\"array\"]","{\"data\":\"object\"}","string"]
But if I tell json_arrayagg to treat it as JSON, the last string member is not handled, resulting in an invalid document:
with t as (
select 'array' data from dual union ALL
select 'object' from dual union all
select 'string' from dual
)
select json_arrayagg(
case data
when 'array' then json_array(data)
when 'object' then json_object('data' value data)
else data
end FORMAT JSON
) json
from t
JSON
------------------------------------------------
[["array"],{"data":"object"},string]
I can't find any function like json_string to JSONify varchar2, and I'd prefer not to do it by hand.
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Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
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