Types of Indices
- Ordered Indices: Search keys are stored in sorted order
- Hash indices: Search keys are distributed uniformly across buckets using a hash function.
Ordered Indices
Primary Index
- In a sequentially ordered fine, the index whose search key specifies a sequential order of the file.
- also known as clustering index
Secondary Index
- an index whose search key specifies an order different from the sequential order of the file
- also known as non-clustering index
Index-Sequential File
ordered sequential file with a primary index
Dense Index
Index record appears for every search-key value in the file
Sparse Index
- Contains index records for only some search key values. (applicable Only when records are sequentially ordered on search key)
- less space and maintenance overhead
- slower than dense index for locating records
Multilevel Index