douts

Question

If only one record satisfies the search condition, then, on the average, a program will read into memory and search half the file blocks before it finds the record. For a file of b blocks, this requires searching (b/2) blocks, on average. If no records or several records satisfy the search condition, the program must read and search all b blocks in the file.

 

anyone can explain the highlighted text with example i can't understand how B/2 block is required to search If only one record satisfies the search condition?

Comments

Data doesn't in the order===> searching means only linear search possible

applying linear search, Best=1,worst=n and average=$\frac{n}{2}$

if your data doesn't have duplicates then average case of linear search ===> $\frac{n}{2}$

if it have duplicates, then you have to search whole ===> n

if it doesn't hve the value, then you have to search whole ===> n

---

You have to study the topic of indexing IN DBMS.
a set of records will reside in the memory block. If you study how indexing work then you will understand