How to INSERT JSON objects in an array in MySQL? - mysql

Question

I am currently assigned to a task to transform our active non-normalized table to a normalized one. We decided to use database triggers to facilitate the bulk migration and succeeding data changes until we discontinue the old table.
Below are the structure and sample of our old table:
SELECT * FROM TabHmIds;
ID EntitlementID TabId HmId
1 101 201 301
2 102 202 302
The required structure and sample of our new table should look like:
SELECT * FROM tab_integration;
id tab_id integration_id metadata
1 201 1 { "paid_id": {"entitlement_id": 101, "id": 301} }
2 202 1 { "paid_id": {"entitlement_id": 202, "id": 302} }
The following is what I have done in my INSERT trigger so far:
CREATE TRIGGER tab_integration_after_insert AFTER INSERT ON `TabHmIds`
FOR EACH ROW
BEGIN
DECLARE var_metadata JSON;
DECLARE var_new_metadata JSON;
DECLARE var_hm_metadata JSON;
DECLARE var_integration_id INT(11);
SELECT
metadata,
integration_id INTO var_metadata,
var_integration_id
FROM
`go`.`tab_integration` gti
WHERE
gti.`tab_id` = NEW.`TabId`;
SET var_hm_metadata = JSON_OBJECT('entitlement_id', NEW.`EntitlementId`, 'id', NEW.`HmId`);
IF var_integration_id = 1 THEN
IF var_metadata IS NULL THEN
SET var_new_metadata = JSON_OBJECT('paid_id', var_hm_metadata);
ELSE
SET #paid_id = JSON_UNQUOTE(JSON_EXTRACT(var_metadata, '$.paid_id'));
SET var_new_metadata = JSON_ARRAY_APPEND(var_metadata, '$.paid_id', var_hm_metadata);
END IF;
END IF;
UPDATE `tab_integration` gti SET `metadata` = var_new_metadata WHERE `tab_id` = NEW.`TabId`;
END
However, what I get is this:
SELECT * FROM tab_integration;
id tab_id integration_id metadata
1 201 1 { "paid_id": "{\"entitlement_id\": 101, \"id\": 301}" }
2 202 1 { "paid_id": "{\"entitlement_id\": 202, \"id\": 302}" }
From the table above, the JSON object is parsed into STRING. I am aware that the JSON_OBJECT parses the passed value to a string. SO I used the JSON_UNQUOTE(JSON_EXTRACT(…)) to convert the paid_id path value to JSON, but it does not get parsed into JSON. I also tried JSON_MERGE_PRESERVE to put the JSON object under the paid_id path but I end up getting:
{“paid_id”: [], “entitlement_id”: 101, “id”: 301 }
I also tried to put the JSON array into a temporary table using JSON_TABLE and modify the values in the temporary and convert that temporary table to JSON using JSONARRAYAGG. But Workbench keeps saying I have an error in my syntax even though I directly copied examples from the web.
I also tried CASTing a well-formed string to JSON, but Workbench also throws a syntax error.
I have spent a week into resolving this data structure in MySQL.
Database scripting is not my strong suit and I am new to the JSON functions in MySQL. Thank you in advance to those who will reply.
If in case needed, my MySQL Workbench is version 10.4.13-MariaDB. But the script should work in MySQL 5.7.

Answer 1

I found the answer to my problem.
Before inserting the new JSON data, I parsed it to CHAR and REPLACEd the characters making it a string. I did the following and it worked!
# After performing the needed JSON manipulations, cleanse the JSON string to JSON.
SET var_new_metadata = CAST(var_new_metadata AS CHAR);
SELECT REPLACE(REPLACE(REPLACE(var_new_metadata, '\\', ''), '\"\{', '{'), '\}\"', '}') INTO var_new_metadata;
After cleansing the data, the UPDATE call still worked and tried to do some JSON manipulations after and, yes, still works!