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Language: Visual FoxPro
Expertise: Beginner

Apr 4, 2000

Question:
What is an index and what is a sort?

Answer:
Here is a table that I will refer to during my answer:

RecNo  cName      nAge
-----  -----      ----
1      Rick       34
2      Dan        30
3      Chris      33

An index is a logical reorganization of the data in a table. The record numbers do not change; the index just allows the table to be viewed in an order other than record number order. If I create an index on the cName field in the table above, here are the results:

RecNo  cName      nAge
-----  -----      ----
3      Chris      33
2      Dan        30
1      Rick       34

Notice that even though Rick appears as the last record, it is still the first record in the table (Recno=1).

A sort is a physical reorganization of the records in a DBF. If I sort the table above by cName, I get the following table:

RecNo  cName      nAge
-----  -----      ----
1      Chris      33
2      Dan        30
3      Rick       34

Notice that the records in the table have been reorganized: record 1 is no longer "Rick."