Couchbase and Oracle have different approaches to database management, with Couchbase utilizing buckets as its core data structure, whereas Oracle uses tables. In Couchbase, documents serve multiple purposes similar to rows in RDBMS, while in Oracle, each row belongs to a single domain. Couchbase's JSON document format allows for flexible schema evolution without the need for explicit column definitions, unlike Oracle. Additionally, Couchbase does not support triggers or sequences, but instead relies on expiry settings and unique constraints to enforce data integrity. Indexing is also handled differently between the two systems, with Couchbase providing a more detailed index mechanism. Overall, these differences highlight distinct design philosophies between the two databases.