UPDATE: This is now possible in MySQL 8 via the JSON_TABLE function: https://dev.mysql.com/doc/refman/8.0/en/json-table-functions.html
I'm loving the new JSON functions in MySQL 5.7, but running into a block trying to merge values from JSON into a normal table structure.
Grabbing JSON, manipulating and extracting arrays from it etc. is simple. JSON_EXTRACT all the way. But what about the inverse, going from a JSON array to rows? Perhaps I am dense on the existing MySQL JSON functionality, but I haven't been able to figure that one out.
For example, say I have a JSON array and want to insert a row for each element in the array with its value? The only way I have found is to write a bunch of JSON_EXTRACT(... '$[0]') JSON_EXTRACT(... '$[1]') etc and union them together.
Or, say I have a JSON array and want to GROUP_CONCAT() it to a single comma separated string?
In other words, I know I can do this:
SET @j = '[1, 2, 3]';
SELECT GROUP_CONCAT(JSON_EXTRACT(@j, CONCAT('$[', x.n, ']'))) AS val
FROM
(
SELECT 0 AS n
UNION
SELECT 1 AS n
UNION
SELECT 2 AS n
UNION
SELECT 3 AS n
UNION
SELECT 4 AS n
UNION
SELECT 5 AS n
) x
WHERE x.n < JSON_LENGTH(@j);
But that hurts my eyes. And my heart.
How can I do something like:
SET @j = '[1, 2, 3]';
SELECT GROUP_CONCAT(JSON_EXTRACT(@j, '$[ * ]'))
... and have it concatenate together the values in the array vs. the JSON array itself?
I guess what I'm looking for here is some sort of JSON_SPLIT along the lines of:
SET @j = '[1, 2, 3]';
SELECT GROUP_CONCAT(val)
FROM
JSON_SPLIT(JSON_EXTRACT(@j, '$[ * ]'), '$')
If MySQL had a proper STRING_SPLIT(val, 'separator') table returning function, I could hack it (escaping be damned), but that's not available either.
Here's how to do this with JSON_TABLE in MySQL 8+:
SELECT *
FROM
JSON_TABLE(
'[5, 6, 7]',
"$[*]"
COLUMNS(
Value INT PATH "$"
)
) data;
You can also use this as a general string split function which MySQL otherwise lacks (similar to PG's regexp_split_to_table or MSSQL's STRING_SPLIT) by taking a delimited string and turning it into a JSON string:
set @delimited = 'a,b,c';
SELECT *
FROM
JSON_TABLE(
CONCAT('["', REPLACE(@delimited, ',', '", "'), '"]'),
"$[*]"
COLUMNS(
Value varchar(50) PATH "$"
)
) data;