I have two databases in MySQL that already have data. they have exactly the same schema. I would like to merge those two databases into one only. I tried:
mysqldump -u root -p --databases database1 database2 database3 > database1_database2_da
However, when I try to open database1_database2_da, I only end up with data from one of the database, but not all of them. I also want to mention that the two databases have their records starting at 1, since they are automatically generated. Do you think there is a way to merge those two databases without losing data from any of them?
Run mysqldump on each database with the --no-create-info option to avoid writing schema information. Then run once on one database with the --no-data option. If you load all of these files sequentially into the same target database, this should work, barring any differences in schema between the two databases or duplicate primary keys.
mysqldump -u root -p --no-create-info database1 > database1.sql
mysqldump -u root -p --no-create-info database2 > database2.sql
mysqldump -u root -p --no-data database1 > schema.sql
After creating a new database, run
mysql -uroot -p -Ddatabase3 < schema.sql
mysql -uroot -p -Ddatabase3 < database1.sql
mysql -uroot -p -Ddatabase3 < database2.sql
This may also work. Don't have a Windows box to test on ATM
type schema.sql database1.sql database2.sql | mysql -uroot -p -Ddatabase3
SQL-Hub (http://sql-hub.com) will let you merge multiple databases with the same schema in to a single database. There is a free licence that will let you do this from the UI though you might need to pay for a license if you want to schedule the process to run automatically. For a one off task with 2 databases you should just be able to do this with the free licence.
来源：https://stackoverflow.com/questions/6526824/can-i-merge-two-databases-into-one-in-mysql-if-they-both-have-the-same-schema