将数据库数据从mssql迁移到mysql

mssql database has the data and I want to move it to mysql database. the tables that the data are coming from are not the same as the tables that i will be putting the data into. what i am thinking of is doing a select then putting the data in a json then inserting it to mysql. this way i know which data is going to which table and to which column. but i am thinking this would be very hard because the data is very big. there is a back up data and it is more than 1gb. so i dont think my solution would be appropriate.mssql database has the data and I want to move