Databases & SQL worksheet with answers

Which rows does WHERE price BETWEEN 10 AND 20 select?

1. ARows with price outside the range 10 to 20
2. BRows with price equal to 10 or 20 only
3. CRows with price above 10 and below 20, excluding 10 and 20
4. DRows with price from 10 to 20, including 10 and 20

Which SQL keyword removes duplicate rows from a result?

1. ASINGLE
2. BDISTINCT
3. CUNIQUE
4. DDIFFERENT

Which SQL statement retrieves data from a table?

1. AUPDATE
2. BCREATE
3. CINSERT
4. DSELECT

Why can a table have only one clustered index?

1. AThe SQL standard forbids more than one index on a table
2. BClustered indexes use too much memory
3. CThe rows can be stored physically in only one order
4. DClustered indexes can only be on the primary key

What does GRANT SELECT ON employees TO alice do?

1. ACopies the employees table to alice
2. BAllows alice to update and delete rows in the employees table
3. CMakes alice the owner of the database
4. DAllows the user alice to read the employees table

Third normal form (3NF) removes:

1. AComposite keys
2. BTransitive dependencies between non-key attributes
3. CAtomic values
4. DRedundant indexes on columns that are not part of a key

Why might a query with WHERE YEAR(order_date) = 2025 not use an index on order_date?

1. AApplying a function to the column prevents a simple index range lookup
2. BIndexes never work with dates
3. CYEAR is not valid SQL
4. DAn index on order_date is only used for ORDER BY clauses, never for WHERE

Which isolation level prevents dirty reads but still allows non-repeatable reads?

1. ARepeatable read
2. BRead committed
3. CSerializable
4. DRead uncommitted