Oracle SQL relies heavily on keys to maintain data integrity and facilitate efficient data retrieval. A primary key uniquely identifies each record, while candidate keys are potential alternatives that meet uniqueness and non-null requirements. Foreign keys establish relationships between tables, ensuring referential integrity. Composite keys consist of multiple columns, used when a single column is insufficient for unique identification. Unique keys ensure distinct values, allowing one null value, while surrogate keys substitute for natural primary keys. Understanding these key types is essential for designing robust database schemas.

Source: https://dev.to/mrcaption49/keys-in-sql-1e2b