Correct Answer - Option 3 : Compute the certesian product between the STUDENT and COURSE relations
Concept
Cartesian Product
It is also an operator that works on two sets. It is sometimes called the CROSS PRODUCT or CROSS JOIN. It combines the tuples of one relation with all the tuples of the other relation.
Syntax
table_name1 × table_name2
Example
Table 1
Table 2
Cartesian Product = Table1 × Table2
| A |
1 |
A |
1 |
| A |
1 |
B |
2 |
| A |
1 |
C |
3 |
| B |
2 |
A |
1 |
| B |
2 |
B |
2 |
| B |
2 |
C |
3 |
| C |
3 |
A |
1 |
| C |
3 |
B |
2 |
| C |
3 |
C |
3 |
Important Points
Natural Join
It is also known as equijoin. Such joins result in two attributes in the resulting relation having exactly the same value. A `natural join' will remove the duplicate attribute(s). the natural join will require that the attributes have the same name to identify the attribute(s) to be used in the join.
Outer Joins
An outer join retains the information that would have been lost from the tables, replacing missing data with nulls.
There are three forms of the outer join, depending on which data is to be kept.
- LEFT OUTER JOIN - keep data from the left-hand table
- RIGHT OUTER JOIN - keep data from the right-hand table
- FULL OUTER JOIN - keep data from both tables
