I need to get the counts of all elements from a JSON made through a MySQL query.
In this case, 6 elements.

You could change your SQL query to return the number of results:

SELECT COUNT(1)
FROM leads
WHERE (UNIX…

You could create a Function node directly behind this node, and populate it with the following code:

var length = items.length;
result = [ { "json" : { "length": length } } ];
return result;