Databases & SQL worksheet with answers

Which SQL statement retrieves data from a table?

1. AINSERT
2. BUPDATE
3. CSELECT
4. DCREATE

What does a CROSS JOIN return?

1. AOnly rows that do not match
2. BThe rows of the first table only
3. COnly the rows that match on a shared key column
4. DEvery combination of rows from the two tables

What does COMMIT do in a transaction?

1. AStarts a new table
2. BUndoes all changes made since the transaction began
3. CLocks the whole database
4. DMakes all changes of the transaction permanent

What is SQL injection?

1. AA database backup technique
2. BA technique for inserting many rows quickly with a single INSERT statement
3. CA way to add indexes
4. DAn attack where user input changes the structure of a SQL query

First normal form (1NF) requires that:

1. AEvery table has exactly one column
2. BEach column contains atomic values and there are no repeating groups
3. CEvery non-key column depends on the whole key and on nothing but the key
4. DThere are no foreign keys

Which ACID property guarantees that committed changes survive a system crash?

1. AAtomicity
2. BIsolation
3. CConsistency
4. DDurability

Table employee(emp_id, dept_id, dept_name) has the key emp_id, and dept_id → dept_name. Which statement is correct?

1. AIt is not in 1NF
2. BIt is in BCNF and therefore in 3NF
3. CIt is in 2NF but not in 3NF
4. DIt is not in 2NF

With multiversion concurrency control (MVCC), how can readers avoid blocking writers?

1. AReaders see a consistent snapshot of committed row versions while writers create new versions
2. BReaders always wait until all writers have committed
3. CWriters are not allowed while any reader is active
4. DReaders read uncommitted data directly