Excel spreadsheets can be stored as BLOB data.
Store Excel spreadsheets in DB2 BLOB
Store Excel spreadsheets in Oracle BLOB
Store Excel spreadsheets in SQL Server VARBINARY
Store Excel spreadsheets in MySQL BLOB
Store Excel spreadsheets in PostgreSQL BYTEA
Store Excel spreadsheets in SQLite BLOB
DBBlobEditor can help you to store Excel spreadsheets as BLOB data.