Chapter 9 Give three criteria for when a column should be indexed. Describe refe
ID: 3837692 • Letter: C
Question
Chapter 9
Give three criteria for when a column should be indexed.
Describe referential integrity.
Explain how Oracle uses declarative referential integrity to prevent deletion, insertion, and update problems.
Explain how normalizing a database to the third normal form affects database performance.
Chapter 10
Describe how each of these types of constraints restricts the values that can be stored in a table: not null, unique, primary key, foreign key, and check.
Describe the difference between a column-level constraint and a table-level constraint.
Explanation / Answer
constraints:
if we put constratints they will restricts the data which is to be inserted
notnull constraint:
if we put notnull constraint then we cannot insert null values in to the coloumns
unique:
if we have unique constraint then there should nott be similar values in that colomn
primary key :
if we have primary key constraints then it identifies the record uniquely and cannot contain
NULL values
forgien key:
it will shows the relation between one table to another table primary key
check:
the check constraint is used to restrict limit or range of the values that should be inserted
chapter 10:
difference between column-level constratint and table level constraint
1)these coloumns level constraints will applied to the specified coloumn but table level constraint are
applied to entire table
2)any column constraints can be expressed in table level but we cannot do similar in table level
constraint