Database Redesign(Database ) Questions and Answers

Question 1. What SQL command can be used to delete columns from a table?
  1.    MODIFY TABLE TableName DROP COLUMN ColumnName
  2.    MODIFY TABLE TableName DROP ColumnName
  3.    ALTER TABLE TableName DROP COLUMN ColumnName
  4.    ALTER TABLE TableName DROP ColumnName
Explanation:-
Answer: Option C. -> ALTER TABLE TableName DROP COLUMN ColumnName
Question 2. Which of the following SQL statements are helpful in database redesign?
  1.    Correlated subqueries only
  2.    EXISTS/NOT EXISTS expressions only
  3.    Both of the above are helpful
  4.    None of the above are helpful
Explanation:-
Answer: Option C. -> Both of the above are helpful
Question 3. Which SQL-92 standard SQL command can be used to change a table name?
  1.    RENAME TABLE
  2.    CHANGE TABLE
  3.    ALTER TABLE
  4.    None of the above is correct
Explanation:-
Answer: Option D. -> None of the above is correct
Question 4. The process of reading a database schema and producing a data model from that schema is known as:
  1.    data modeling.
  2.    database design.
  3.    reverse engineering.
  4.    None of the above is correct.
Explanation:-
Answer: Option C. -> reverse engineering.
Question 5. Database redesign is not terribly difficult if the:
  1.    database is structured.
  2.    database is well-designed.
  3.    database has no data.
  4.    database is relatively small.
Explanation:-
Answer: Option C. -> database has no data.
Question 6. The NOT EXISTS keyword will be true if:
  1.    any row in the subquery meets the condition.
  2.    all rows in the subquery fail the condition.
  3.    both of these two conditions are met.
  4.    neither of these two conditions is met.
Explanation:-
Answer: Option B. -> all rows in the subquery fail the condition.
Question 7. The EXISTS keyword will be true if:
  1.    any row in the subquery meets the condition only.
  2.    all rows in the subquery fail the condition only.
  3.    both of these two conditions are met.
  4.    neither of these two conditions is met.
Explanation:-
Answer: Option A. -> any row in the subquery meets the condition only.
Question 8. Changing cardinalities in a database is:
  1.    a common database design task.
  2.    a rare database design task, but does occur.
  3.    a database design task that never occurs.
  4.    is impossible to do, so a new database must be constructed and the data moved into it.
Explanation:-
Answer: Option A. -> a common database design task.
Question 9. To drop a column that is used as a foreign key, first:
  1.    drop the primary key.
  2.    drop the table containing the foreign key.
  3.    drop the foreign key constraint.
  4.    All of the above must be done.
Explanation:-
Answer: Option C. -> drop the foreign key constraint.
Question 10. The data model that is produced from reverse engineering is:
  1.    a conceptual model.
  2.    an internal model.
  3.    a logical model.
  4.    None of the above is correct.
Explanation:-
Answer: Option D. -> None of the above is correct.
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