Set - 7

Question 6 :

What is the difference between deleting and truncating of tables

Answer :

Deleting a table will not remove the rows from the table but entry is there in the database dictionary and it can be retrieved But truncating a table deletes it completely and it cannot be retrieved.


Question 7 :

What are mutating tables

Answer :

When a table is in state of transition it is said to be mutating. eg :: If a row has been deleted then the table is said to be mutating and no operations can be done on the table except select.


Question 8 :

What are Codd Rules

Answer :

Codd Rules describe the ideal nature of a RDBMS. No RDBMS satisfies all the 12 codd rules and Oracle Satisfies 11 of the 12 rules and is the only Rdbms to satisfy the maximum number of rules.


Question 9 :

What is Normalisation

Answer :

Normalisation is the process of organising the tables to remove the redundancy.There are mainly 5 Normalisation rules.
a) 1 Normal Form :: A table is said to be in 1st Normal Form when the attributes are atomic
b) 2 Normal Form :: A table is said to be in 2nd Normal Form when all the candidate keys are dependant on the primary key
c) 3rd Normal Form :: A table is said to be third Normal form when it is not dependant transitively


Question 10 :

What is the Difference between a post query and a pre query

Answer :

A post query will fire for every row that is fetched but the pre query will fire only once.