How to convert a JSON array to comma separated string in MySQL?

Question

I've a JSON column from where I'm extracting values. All goes good, except I'm not able to convert an array inside the JSON Object to a comma separated string. Below is the structure similar to what I have.

id	name	data
...	...	...
234	AAA	{ "..." "options": [ "Option A", "Option B", "Option C" ], "..." }
...	...	...

Now I'm extracting the data like this:

SELECT
    `id`,
    `name`,
    JSON_UNQUOTE( JSON_EXTRACT( `data`, '$.options' ) ) AS `options`
FROM `my_table`;

Result I'm getting:

id	name	data
...	...	...
234	AAA	["Option A", "Option B", "Option C"]
...	...	...

Result I want:

id	name	data
...	...	...
234	AAA	"Option A", "Option B", "Option C"
...	...	...

How can I do this in MySQL? It's like implode function in php.

I've seen some answers that uses nested REPLACE but remember that the value itself may contain square brackets.

Answer 1

Assuming you are using mysql 8.0 then you can use JSON_TABLE with CROSS JOIN and GROUP_CONCAT to achieve this:

Try below query:

select t1.id,t1.name, group_concat(t2.data_ )
from test t1 
cross join 
json_table(t1.data->'$.options', '$[*]' columns(data_ varchar(10) path '$'))t2
group by 1,2

If you want to surround all the values in quotes then replace group_concat(t2.data_ ) with group_concat(concat('"',t2.data_,'"' )) in above query

Explanation

In your question you want to get the values of options array of the JSON in to comma separated string. So the steps of the solution is:

Step 1. Get the array data from JSON: Here by using -> operator we are able to fetch the data from data field. data->'$.options' will return the array in JSON format.

Step 2. Unnest all the elements of the array: Here JSON_TABLE ( Reference ) will do the things for us. see below example

select * from json_table(
'["Option A","Option B","Option C"]', 
'$[*]' columns(data_ varchar(10) path '$'))t

Result:

data_
Option A
Option B
Option C

Step 3. Cross join the unnest records: After unnest the array CROSS JOIN it with main table, which will return one row against each records returns by JSON_TABLE . In below example you will get 3 rows against id 234 because there are 3 elements in array.

select t1.id,t1.name,t2.data_
from test t1 
cross join 
json_table(t1.data->'$.options', '$[*]' columns(data_ varchar(10) path '$'))t2

Result:

id    name      data_
234   AAA       Option A
234   AAA       Option B
234   AAA       Option C

Step 4. Group the results: In final step use GROUP_CONCAT ( Reference ) to group all the records by id , name etc. to get the desired output.

DEMO