Correct Answer - Option 2 : Join
Symbol
|
Name
|
Example
|
σ
|
selection
|
σA = 500(R) → Return rows whose A attribute is equal to 500 and no duplicates are allowed
|
∏
|
Projection
|
∏B(R) → Output the column B and no duplicate are allowed
|
⋈
|
natural join
|
R ⋈ S → Output pairs of rows from the two input relations that have the same value on all attributes that have the same value
|
×
|
cartesian product
|
R × S → Output all pairs of rows from the two input relations
|
Conclusions:
Select and project is applied to one table.
cartesian product requires two tables but need not have common attributes
Join or natural join or full outer join operations requires two tables as input having at least one common column