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Indexed file Vs Sorted file
- Indexed files use a primary key field to identify the records of an original file in a database. A primary key field is a unique field. An indexed file consists of actual records sorted based on the primary key field value
- An indexed file also consists of alternate keys, which build the alternate index. Unlike primary keys, the alternate keys in an indexed file do not have actual records.
- The advantage of primary key field values is that because of the indexing of actual records, you require only one input-output operation to access records in an indexed file
- Sorting is like placing records either in ascending or descending order based on KEY
- For example, sorting payroll-file with an employee identification number in ascending order is called Soring. Here, employee identification is KEY.
- Sorting is possible to do on multiple keys like ID and Department
- When you sort a sequential file, its records are stored on the hard disk and you can only access them serially. It is not possible to access all the records of a file simultaneously.