SQL allows duplicate tuples in relations, and correspondingly defines the multiplicity of tuples in the result of joins. Which one of the following queries always gives the same answer as the nested query shown below:

Select * from R where a in (select S.a from S)

Consider a join (relation algebra) between relations r(R)and s(S) using the nested loop method. There are 3 buffers each of size equal to disk block size, out of which one buffer is reserved for intermediate results. Assuming size(r(R)) < size(s(S)), the join will have fewer number of disk block accesses if

Consider the following schedule S of transactions T1, T2, T3, T4:

Given an instance of the STUDENTS relation as shown below:

For (StudentName, StudentAge) to be a key for this instance, the value $$X$$ should NOT be equal to ________.