Operation on Files
- 1. RDBMS THEORY UNIT – 1 Operation on Files Mr.S.Viswanathan 30-07-2021 Mr.S.Viswanathan, Assistant Professor, Department of Information Technology
- 2. Operation on Files • There are mainly two kinds of file operations 1) Retrieval 2) Update 1) Retrieval – It doen’t change the content of the file. 2) Update - It change the file by, * Modifying the records * deleting the records * Inserting new records. 30-07-2021 Mr.S.Viswanathan, Assistant Professor, Department of Information Technology
- 3. Cont… • There are several operations are available. They are, 1) Find (Locate) 2) Read 3) ReadNext (Or) GetNext 4) Modify 5) Insert 6) Delete 30-07-2021 Mr.S.Viswanathan, Assistant Professor, Department of Information Technology
- 4. Find (Locate) • This operation is to locate the record. • First the records transferred to main memory and records are searched. • The search continues until the end of the file. 30-07-2021 Mr.S.Viswanathan, Assistant Professor, Department of Information Technology
- 5. Read • It is also referred as “GET”. • The records are copied from the memory to a program variable. • In some cases the pointer to next record is used in the “result set”. 30-07-2021 Mr.S.Viswanathan, Assistant Professor, Department of Information Technology
- 6. ReadNext (Or) GetNext • It Searched for the next record. • When matches the selection condition, the record are copied to the program variable. 30-07-2021 Mr.S.Viswanathan, Assistant Professor, Department of Information Technology
- 7. Modify • It is also known as Update. • It modifies the field values of the current record. • Then it modifies the record back to disk. 30-07-2021 Mr.S.Viswanathan, Assistant Professor, Department of Information Technology
- 8. Insert • It inserts as new record to file. • It involves many processes like, 1) Finding a place to insert. 2) Writing the new record to disk. 3) Updating the index entries. 4) Updating the record headers. 30-07-2021 Mr.S.Viswanathan, Assistant Professor, Department of Information Technology
- 9. Delete • It deletes the current record. • Updates the file on the disk to reflect the deletion 30-07-2021 Mr.S.Viswanathan, Assistant Professor, Department of Information Technology
- 10. **********************Thank You********************* 30-07-2021 Mr.S.Viswanathan, Assistant Professor, Department of Information Technology