Database Interview Questions and Answers
Question - 81 : - Define database model.
Answer - 81 : -
A data model determining fundamentally how data can be stored, manipulated and organised and the structure of the database logically is called database model.
Question - 82 : - Define Normalization.
Answer - 82 : -
Organized data void of inconsistent dependency and redundancy within a database is called normalization.
Question - 83 : - Enlist the advantages of normalizing database.
Answer - 83 : -
Advantages of normalizing database are:
- No duplicate entries
- Saves storage space
- Boasts the query performances.
Question - 84 : - Define Denormalization.
Answer - 84 : -
Boosting up database performance, adding of redundant data which in turn helps rid of complex data is called denormalization.
Question - 85 : - Enlist some commands of DDL.
Answer - 85 : -
They are:
CREATE:
Create is used in the CREATE TABLE statement. Syntax is:
CREATE TABLE [column name] ( [column definitions] ) [ table parameters]
ALTER:
It helps in modification of an existing object of database. Its syntax is:
ALTER objecttype objectname parameters.
DROP:
It destroys an existing database, index, table or view. Its syntax is:
DROP objecttype objectname.
Question - 86 : - Define Union All operator and Union.
Answer - 86 : -
Full recordings of two tables is Union All operator.A distinct recording of two tables is Union.
Question - 87 : - Define cursor.
Answer - 87 : -
A database object which helps in manipulating data row by row representing a result set is called cursor.
Question - 88 : - Enlist the cursor types.
Answer - 88 : -
They are:
- Dynamic: it reflects changes while scrolling.
- Static: doesn’t reflect changes while scrolling and works on recording of snapshot.
- Keyset: data modification without reflection of new data is seen.
Question - 89 : - Define sub-query.
Answer - 89 : -
A query contained by a query is called Sub-query.
Question - 90 : - Why is group-clause used?
Answer - 90 : -
Group-clause uses aggregate values to be derived by collecting similar data.