Bitmap Indices (Cont.) In its simplest form a bitmap index on an attribute has a bitmap for each value of the attribute Bitmap has as many bits as records In a bitmap for value v,the bit for a record is 1 if the record has the value v for the attribute,and is 0 otherwise Bitmaps for gender Bitmaps for record income level m 10010 number ID gender income level L1 10100 0 76766 m L1 01101 1 22222 f L2 L2 01000 12121 L1 L3 00001 3 15151 m L4 L4 00010 4 58583 f L3 L5 00000 Database System Concepts-7th Edition 24.12 @Silberschatz,Korth and SudarshanDatabase System Concepts - 7 24.12 ©Silberschatz, Korth and Sudarshan th Edition Bitmap Indices (Cont.) ▪ In its simplest form a bitmap index on an attribute has a bitmap for each value of the attribute • Bitmap has as many bits as records • In a bitmap for value v, the bit for a record is 1 if the record has the value v for the attribute, and is 0 otherwise