chap indexing secondary key primary key jones aa smith ab zukowski ab ff ax ax zx zq figure illustration of an inverted list each secondary key value is stored in the secondary key list each secondary key value on the list has pointer to list of the primary keys whose associated records have that secondary key value secondary key index primary key next jones aa smith ax zukowski zx zq ab ab ax ff figure an inverted list implemented as an array of secondary keys and combined lists of primary keys each record in the secondary key array contains pointer to record in the primary key array the next field of the primary key array indicates the next record with that secondary key value