Write the following queries in relational algebra, using the university schema.
3. Find the names of all students who have taken at least one Comp. Sci. course.
b. Find the IDs and names of all students who have not taken any course offering bef
When is it preferable to use a dense index rather than a sparse index?
Explain your answer.
It is preferable to use a dense index instead of a sparse index when the file is not sorted on the indexed
eld (such as when the index is a sec
Explain the distinctions among the terms primary key, candidate key. and superkey.
A superkey is a set of one or more attributes that, taken collectively, allows us to identify uniquely an entity
in the entity set. A superkey may conta
Consider the bank database of Figure 2.15.
a. What are the appropriate primary keys?
b. Given your choice of primary keys, identify appropriate foreign keys.
Reference Figure 2.15:
branch(branch.name, branchxity, assets)
For the database of Figure 4.11, write a query to find those employees with no manager. Note that an
employee may simply have no manager listed or may have a null manager. Write your query using an outer
join and then write it again using no out
List four applications you have used that most likely employed database system to store persistent data
- Banking: For account information, transfer of funds, banking transactions.
. Universities: For student information, online assignm