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databases Online Quiz - 115

Description: databases Online Quiz - 115
Number of Questions: 20
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Tags: databases
Attempted 0/20 Correct 0 Score 0
  1. The right table will return ALL rows.

  2. The right table will return NULL.

  3. Both tables will return NULL.

  4. The left table will return ALL rows.

  5. The left table will return NULL.


Correct Option: D
  1. Structure

  2. Design issue

  3. Data source

  4. Storage issue

  5. Operational process


Correct Option: B

Which one of the following is NOT a characteristic of metadata?

  1. Data about data

  2. Describes a data dictionary

  3. Self-describing

  4. Includes user data

  5. Supports its own structure


Correct Option: D
  1. Encryption key management

  2. Graphical User Interface Widgets

  3. Thread creation, execution, & coordination

  4. Network socket creation/operation

  5. If/Then, for, do/while statements


Correct Option: E

What can a mandatory one to one relationship indicate?

  1. More entities are needed.

  2. The model should be denormalized.

  3. The tables are not properly indexed.

  4. The model cannot be implemented physically.

  5. More attributes are needed.


Correct Option: E

AI Explanation

To answer this question, we need to understand the concept of a mandatory one-to-one relationship in database modeling.

A mandatory one-to-one relationship indicates that each entity in one table must be associated with exactly one entity in another table, and vice versa. In other words, it means that every record in one table must have a corresponding record in the other table, and vice versa.

Let's go through each option to determine which one is correct:

Option A) More entities are needed - This option is incorrect. A mandatory one-to-one relationship does not imply that more entities are needed. It simply means that each entity in one table must have a corresponding entity in another table.

Option B) The model should be denormalized - This option is incorrect. A mandatory one-to-one relationship does not necessarily indicate that the model should be denormalized. Denormalization is a technique used to improve performance in certain situations, but it is not directly related to the presence of a mandatory one-to-one relationship.

Option C) The tables are not properly indexed - This option is incorrect. The presence of a mandatory one-to-one relationship does not necessarily indicate that the tables are not properly indexed. Indexing is a separate concept that is used to improve the performance of database queries.

Option D) The model cannot be implemented physically - This option is incorrect. A mandatory one-to-one relationship does not imply that the model cannot be implemented physically. It simply means that there is a requirement for a one-to-one relationship between entities in two tables.

Option E) More attributes are needed - This option is correct. A mandatory one-to-one relationship can indicate that more attributes are needed in either of the tables involved in the relationship. Since each entity in one table must be associated with exactly one entity in the other table, it may require additional attributes to properly capture the relationship.

Therefore, the correct answer is option E) More attributes are needed. This option is correct because a mandatory one-to-one relationship can indicate that additional attributes are needed in either of the tables involved in the relationship.

You are running a query against a relational database. Referring to the scenario above, what clause or command do you use in the query to help avoid a costly tablescan?

  1. GROUP BY clause

  2. INDEX command

  3. HAVING clause

  4. FROM clause

  5. WHERE clause [/quote]


Correct Option: B

AI Explanation

To answer this question, you need to understand how to optimize query performance in a relational database.

The correct answer is B) INDEX command.

The INDEX command is used to create an index on one or more columns of a table, which helps improve query performance by allowing the database to quickly locate the rows that satisfy a certain condition. When an index is created, the database creates a separate data structure that stores the indexed column(s) in a sorted order, making it faster to search for specific values.

The other options are incorrect:

A) GROUP BY clause - The GROUP BY clause is used to group rows that have the same values in specific columns. While it can help organize the data for aggregation functions, it does not directly optimize query performance.

C) HAVING clause - The HAVING clause is used to filter the results of a query based on a condition applied to the grouped data. Similar to the GROUP BY clause, it is used for data manipulation rather than optimization.

D) FROM clause - The FROM clause is used to specify the table(s) from which you want to retrieve data in a query. It does not directly optimize query performance.

E) WHERE clause - The WHERE clause is used to specify the conditions that must be met for a row to be included in the result set. While it can help filter the data, it does not directly optimize query performance.

Therefore, the correct answer is B) INDEX command because it is specifically used to improve query performance by creating an index on one or more columns of a table.

The query performance increases by using NOT operator.

  1. True

  2. False


Correct Option: B

NULL values are ingnored for all SQ: 2008 aggregate functions.

  1. True

  2. False


Correct Option: A

The query performance increases by using NOT operator.

  1. True

  2. False


Correct Option: B

NULL values are ingnored for all SQL: 2008 aggregate functions.

  1. True

  2. False


Correct Option: A
  1. STDDEV

  2. VARIANCE

  3. ROUND

  4. COUNT


Correct Option: C

which of this Operator Precedence is correct??

    • , + (Unary operators, negation)
    • , / (Multiplication, division)
  1. +, - , || (Addition, subtraction, concatenation)

  2. NONE of these


Correct Option: A,B,C
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