MySQL Router balances client connections between the available nodes in a MySQL InnoDB Cluster, ensuring that client requests are routed to healthy nodes and maintaining high availability even during node failures.

The InnoDB Storage Engine ensures data integrity by providing transaction support and crash recovery features. It uses transaction logs to recover data in case of a crash and ensures ACID compliance for data integrity.

An INNER JOIN returns only the rows that have matching values in both tables. If no match is found, the row is excluded from the result set.

MySQL Router routes traffic to available and healthy nodes in a MySQL InnoDB Cluster, ensuring high availability by distributing client connections to functioning servers.

In MySQL Group Replication, if the primary server fails, the group automatically selects a new primary server, ensuring continuous availability without manual intervention.