How to merge two tables into one using mongify - mysql

Question

I am planning to migrate my application database from Mysql to Mongo with low schema changes. In my new schema I merged two Mysql tables into one Mongo collection. I want to use mongify (https://github.com/anlek/mongify) gem to populate my existing Mysql data into Mongo with newer schema.
How to do this? Is there a way in mongify to merge two Mysql tables into one?
Mysql tables
user
id
name
nickname
type
user_role
id
role
alias
user_id
I merged the above two tables into single collection in Mongo
user
id
name
type
role
alias

Answer 1

Try Left Join: (Tables will be merged)
SELECT column_name(s)
FROM table1
LEFT JOIN table2
ON table1.column_name=table2.column_name;
Export that data to sql format and upload it to mongodb
SELECT country INTO customerCountry
FROM customers
WHERE customerNumber = p_customerNumber;
CASE customerCountry -- Here you have to see if that alias data is set
WHEN 'USA' THEN
SET p_shiping = '2-day Shipping'; -- here you have to write Update Query
ELSE
SET p_shiping = '5-day Shipping';
END CASE;
I think it might help you

Answer 2

Fetch the data using JOIN from MySQL and load that data into MongoDB:
Try this:
SELECT U.id, U.name, U.type, UR.role
FROM USER U
INNER JOIN user_role UR ON U.id = UR.user_id;

Answer 3

An alternative if its difficult to merge two tables ad-hoc then run a mongo shell script post-hoc; they are very easy to program (couple o' lines of js) and simple to execute. plus one can apply any needed conversion, such as into json/bson arrays permitted in mongo but not the mysql.
assuming a user and user_role collection (or table) in mongo.
db.user_role.find({}).forEach(function(doc) {
var roles = doc.roles;
// convert mysql format here if needed.
//var roles_array = JSON.parse(roles) // or whatever?
//var alias = doc.alias;
// if alias is null empty or ??
// dont upsert to avoid orphaned user_role records
db.user.update({"_id": doc.user_id}, {"roles": roles, "alias", doc.alias }, {upsert: false, multi: false});
}
Then execute using the mongo shell
mongo localhost:27017/test myjsfile.js