Tag: databases

Questions Related to databases

Which of the following is NOT a benefit of indexes?
technology databases

  1. Faster operation during INSERT commands

  2. Faster operation during UPDATE commands

  3. Faster operation during SELECT commands

  4. Faster operation during DELETE commands

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Correct Option: D

Which of the following commands will rename a table?
technology databases

  1. RENAME table_name new_table_name;

  2. RENAME table_name TO new_table_name;

  3. RENAME TABLE table_name new_table_name;

  4. RENAME TABLE table_name TO new_table_name;

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Correct Option: B

Which command lets you put data into more than one table using a single command?
technology databases

  1. MERGE

  2. INSERT INTO MANY

  3. MULTIADD

  4. INSERT ALL INTO

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Correct Option: D

Examine the SQL statement that creates ORDERS table: CREATE TABLE orders (SER_NO NUMBER UNIQUE, ORDER_ID NUMBER, ORDER_DATE DATE NOT NULL, STATUS VARCHAR2(10) CHECK (status IN ('CREDIT', 'CASH')), PROD_ID NUMBER REFERENCES PRODUCTS(PRODUCT_ID), ORD_TOTAL NUMBER, PRIMARY KEY (order_id, order_date)); For which columns would an index be automatically created when you execute the above SQL statement?
technology databases

  1. SER_NO

  2. ORDER_ID

  3. STATUS

  4. PROD_ID

  5. ORD_TOTAL

  6. composite index on ORDER_ID and ORDER_DATE

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Correct Option: A,F

Which three are DATETIME data types that can be used when specifying column definitions? (Choose three.)

technology databases

  1. TIMESTAMP

  2. INTERVAL MONTH TO DAY

  3. INTERVAL DAY TO SECOND

  4. INTERVAL YEAR TO MONTH

  5. TIMESTAMP WITH DATABASE TIMEZONE

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Correct Option: A,C,D

Evaluate the SQL statement: TRUNCATE TABLE DEPT; Which three are true about the SQL statement? (Choose three.) A. It releases the storage space used by the table. B. It does not release the storage space used by the table. C. You can roll back the deletion of rows after the statement executes. D. You can NOT roll back the deletion of rows after the statement executes. E. An attempt to use DESCRIBE on the DEPT table after the TRUNCATE statement executes will display an error. F. You must be the owner of the table or have DELETE ANY TABLE system privileges to truncate the DEPT table.
technology databases

  1. A

  2. B

  3. C

  4. D

  5. E

  6. F

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Correct Option: A,D,F

Which two statements about sequences are true? (Choose two.) A. You use a NEXTVAL pseudo column to look at the next possible value that would be generated from a sequence, without actually retrieving the value. B. You use a CURRVAL pseudo column to look at the current value just generated from a sequence, without affecting the further values to be generated from the sequence. C. You use a NEXTVAL pseudo column to obtain the next possible value from a sequence by actually retrieving the value from the sequence. D. You use a CURRVAL pseudo column to generate a value from a sequence that would be used for a specified database column. E. If a sequence starting from a value 100 and incremented by 1 is used by more than one application, then all of these applications could have a value of 105 assigned to their column whose value is being generated by the sequence. F. You use a REUSE clause when creating a sequence to restart the sequence once it generates the maximum value defined for the sequence.
technology databases

  1. A

  2. B

  3. C

  4. D

  5. E

  6. F

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Correct Option: B,C

Which SQL statement generates the alias Annual Salary for the calculated column SALARY*12? A. SELECT ename, salary*12 'Annual Salary' FROM employees; B. SELECT ename, salary*12 "Annual Salary" FROM employees; C. SELECT ename, salary*12 AS Annual Salary FROM employees; D. SELECT ename, salary*12 AS INITCAP("ANNUAL SALARY") FROM employees
technology databases

  1. A

  2. B

  3. C

  4. D

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Correct Option: B

Which SQL statement accepts user input for the columns to be displayed, the table name, and the WHERE condition? A. SELECT &1, "&2" FROM &3 WHERE last_name = '&4'; B. SELECT &1, '&2' FROM &3 WHERE '&last_name = '&4''; C. SELECT &1, &2 FROM &3 WHERE last_name = '&4'; D. SELECT &1, '&2' FROM EMP WHERE last_name = '&4';
technology databases

  1. A

  2. B

  3. C

  4. D

Show answer
Correct Option: C

In which scenario would an index be most useful? A. The indexed column is declared as NOT NULL. B. The indexed columns are used in the FROM clause. C. The indexed columns are part of an expression. D. The indexed column contains a wide range of values.

technology databases

  1. A

  2. B

  3. C

  4. D

Show answer
Correct Option: D

AI Explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) The indexed column is declared as NOT NULL - This option is incorrect because declaring a column as NOT NULL does not necessarily make an index more useful. A NOT NULL constraint ensures that the column cannot have null values, but it does not directly affect the usefulness of an index.

Option B) The indexed columns are used in the FROM clause - This option is incorrect because using indexed columns in the FROM clause does not necessarily make an index more useful. The FROM clause is used to specify the tables from which to retrieve data, and while indexes can be used to optimize the retrieval of data, using indexed columns in the FROM clause alone does not guarantee the usefulness of an index.

Option C) The indexed columns are part of an expression - This option is incorrect because having indexed columns as part of an expression does not necessarily make an index more useful. While indexes can be used to optimize the evaluation of expressions, having indexed columns as part of an expression alone does not guarantee the usefulness of an index.

Option D) The indexed column contains a wide range of values - This option is correct because when the indexed column contains a wide range of values, an index can be more useful. Indexes are particularly effective when the indexed column has a large number of distinct values. A wide range of values in the indexed column allows for better selectivity, meaning that the index can filter out a larger portion of the data, resulting in improved query performance.

The correct answer is D. The indexed column contains a wide range of values. This option is correct because having a wide range of values in the indexed column makes an index more useful.