Ordered Indices In an ordered index,index entries are stored sorted on the search key value. Clustering index:in a sequentially ordered file,the index whose search key specifies the sequential order of the file. Also called primary index The search key of a primary index is usually but not necessarily the primary key. Secondary index:an index whose search key specifies an order different from the sequential order of the file.Also called nonclustering index. ■ Index-sequential file:sequential file ordered on a search key,with a clustering index on the search key. Database System Concepts-7th Edition 14.5 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 14.5 ©Silberschatz, Korth and Sudarshan th Edition Ordered Indices ▪ In an ordered index, index entries are stored sorted on the search key value. ▪ Clustering index: in a sequentially ordered file, the index whose search key specifies the sequential order of the file. • Also called primary index • The search key of a primary index is usually but not necessarily the primary key. ▪ Secondary index: an index whose search key specifies an order different from the sequential order of the file. Also called nonclustering index. ▪ Index-sequential file: sequential file ordered on a search key, with a clustering index on the search key