if a table contains a primary key there can be no duplicate records in a table
Table (database) In terms of the relational model of databases, a table can be considered a convenient representation of a relation, but the two are not strictly equivalent. For instance, an SQL table can potentially contain duplicate rows, whereas a true relation cannot contain duplicate tuples. Similarly, representation as a table implies a particular ordering to the rows and columns, whereas a relation is explicitly unordered. However, the database system does not guarantee any ordering of the rows unless an ORDER BY clause is specified in the SELECT statement that queries the table.
Guinness World Records The book itself holds a world record, as the best-selling copyrighted book of all time. As of the 2017 edition, it is now in its 62nd year of publication, published in 100 countries and 23 languages. The international franchise has extended beyond print to include television series and museums. The popularity of the franchise has resulted in Guinness World Records becoming the primary international authority on the cataloguing and verification of a huge number of world records; the organisation employs official record adjudicators authorised to verify the authenticity of the setting and breaking of records.[2]