## Inversion List

An inversion list is part of an index. An inversion list consists of a secondary key and the related primary key(s).

A table contains the names of all customers in a hotel. You have defined the primary key for this table as the customer number cno.

cno | surname | firstname
2003 | Miller | Frank
2011 | Griffith | Mary
2078 | Miller | Jane
2104 | Miller | Susan
2295 | Miller | Sally

Now define an index for the surname column. The surname column now becomes an indexed column (also known as an inverted column).

The index contains the following inversion lists:

¡ an inversion list with the secondary key Griffith and the primary key 2011 (the surname Griffith only appears once in the table)

¡ a further inversion list with the secondary key Miller and the primary keys 2003, 2078, 2104, and 2295 (the surname Miller appears four times in the table)