SQLs DML And DDL

Question 1

How do we insert data in SQL?

Answer 1

INSERT
Add list of attributes to relation name
Can insert entire result of query into relation

Question 2

How do we delete data in SQL?

Answer 2

DELETE

Deletes tuples satisfying condition or deletes all

Question 3

How do we update data in SQL?

Answer 3

UPDATE

Change certain attributes in certain tuples

Question 4

How does the DDL of SQL work?

Answer 4

Database schema comprises declarations for relations of database

Question 5

What are the elements of the table declaration in DDL for SQL?

Answer 5

Integer
Float
Char
Varchar

Question 6

How do we view data in SQL?

Answer 6

View = virtual table = relation defined in terms of other tables

Question 7

What is a base table?

Answer 7

Relation whose value is really stored in the database

Question 8

How do you use a VIEW?

Answer 8

Interprets query as if base table

Definition of VIEWS used by a query are replaced by algebra

Question 9

What is DMBS optimisation?

Answer 9

Optimises algebraic expression
Pushes selections down tree
Eliminates unnecessary projections