These steps assume that binary logging is enabled on the source
      (which is the default), the replica is using
      TABLE based replication applier metadata
      repositories (which is the default in MySQL 9.0), and
      that you have enabled a replication user and noted the current
      binary log file name and position.
    
      Use a CHANGE REPLICATION SOURCE TO
      statement to configure a replication channel for each source on
      the replica (see Section 19.2.2, “Replication Channels”). The
      FOR CHANNEL clause is used to specify the
      channel. For example, to add source1 and
      source2 as sources to the replica, use the
      mysql client to issue the statement twice on
      the replica, like this:
    
mysql> CHANGE REPLICATION SOURCE TO SOURCE_HOST="source1", SOURCE_USER="ted", SOURCE_PASSWORD="password", \
SOURCE_LOG_FILE='source1-bin.000006', SOURCE_LOG_POS=628 FOR CHANNEL "source_1";
mysql> CHANGE REPLICATION SOURCE TO SOURCE_HOST="source2", SOURCE_USER="ted", SOURCE_PASSWORD="password", \
SOURCE_LOG_FILE='source2-bin.000018', SOURCE_LOG_POS=104 FOR CHANNEL "source_2";
      To make the replica replicate only database db1
      from source1, and only database
      db2 from source2, use the
      mysql client to issue the
      CHANGE REPLICATION FILTER statement
      for each channel, like this:
    
mysql> CHANGE REPLICATION FILTER REPLICATE_WILD_DO_TABLE = ('db1.%') FOR CHANNEL "source_1";
mysql> CHANGE REPLICATION FILTER REPLICATE_WILD_DO_TABLE = ('db2.%') FOR CHANNEL "source_2";
      For the full syntax of the CHANGE REPLICATION
      FILTER statement and other available options, see
      Section 15.4.2.1, “CHANGE REPLICATION FILTER Statement”.