Index Classification (Contd.)

• Composite Search Keys: Search on a combination of fields.

  • Equality query: Every field value is equal to a constant value. E.g. wrt <sal,age> index:
    • age=20 and sal =75
  • Range query: Some field value is not a constant. E.g.:
    • age =20; or age=20 and sal > 10

sue

13

75

bob

cal

joe

12

10

20

80

11

12

name

age

sal

<sal, age>

<age, sal>

<age>

<sal>

12,20

12,10

11,80

13,75

20,12

10,12

75,13

80,11

11

12

12

13

10

20

75

80

Data records

sorted by name

Data entries in index

sorted by <sal,age>

Data entries

sorted by <sal>

Examples of composite key

indexes using lexicographic order.

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