Database Redesign(Computer Science > Database ) Questions and Answers

Question 1. 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 2. 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 3. 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 4. 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 5. 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 6. Before any changes to database structure are attempted one should first:
  1.    clearly understand the current structure and contents of the database only.
  2.    test any changes on a test database only.
  3.    create a complete backup of the operational database only.
  4.    All of the above should be done.
Explanation:-
Answer: Option D. -> All of the above should be done.
Question 7. How can you find rows that do not match some specified condition?
  1.    EXISTS
  2.    Double use of NOT EXISTS
  3.    NOT EXISTS
  4.    None of the above is correct
Explanation:-
Answer: Option B. -> Double use of NOT EXISTS
Question 8. Which of the following modifications may not succeed?
  1.    Changing a column data type from char to date
  2.    Changing a column data type from numeric to char
  3.    Both of the above actions should succeed
  4.    Neither of the above actions will succeed
Explanation:-
Answer: Option A. -> Changing a column data type from char to date
Question 9. A regular subquery can be processed:
  1.    from the top down.
  2.    from the bottom up.
  3.    by nesting.
  4.    None of the above is correct.
Explanation:-
Answer: Option B. -> from the bottom up.
Question 10. What SQL command can be used to add columns to a table?
  1.    MODIFY TABLE TableName ADD COLUMN ColumnName
  2.    MODIFY TABLE TableName ADD ColumnName
  3.    ALTER TABLE TableName ADD COLUMN ColumnName
  4.    ALTER TABLE TableName ADD ColumnName
Explanation:-
Answer: Option D. -> ALTER TABLE TableName ADD ColumnName
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