Tag: databases

Questions Related to databases

Examine the description of the EMPLOYEES table: EMP_ID NUMBER(4) NOT NULL LAST_NAME VARCHAR2(30) NOT NULL FIRST_NAME VARCHAR2(30) DEPT_ID NUMBER(2) JOB_CAT VARCHARD2(30) SALARY NUMBER(8,2) Which statement shows the maximum salary paid in each job category of each department?
technology databases

  1. SELECT dept_id, job_cat, MAX(salary) FROM employees WHERE salary > MAX(salary);

  2. SELECT dept_id, job_cat, MAX(salary) FROM employees GROUP BY dept_id, job_cat;

  3. SELECT dept_id, job_cat, MAX(salary) FROM employees;

  4. SELECT dept_id, job_cat, MAX(salary) FROM employees GROUP BY dept_id;

Show answer
Correct Option: B

Examine the description of the STUDENTS table: STD_ID NUMBER(4) COURSE_ID VARCHARD2(10) START_DATE DATE END_DATE DATE Which two aggregate functions are valid on the START_DATE column? (Choose two)

technology databases

  1. SUM(start_date)

  2. COUNT(start_date)

  3. AVG(start_date, end_date)

  4. MIN(start_date)

Show answer
Correct Option: B,D

AI Explanation

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

Option A) SUM(start_date) - This option is incorrect because the SUM function is used to calculate the sum of numeric values. The START_DATE column is of the DATE data type, which is not a numeric data type.

Option B) COUNT(start_date) - This option is correct. The COUNT function is used to count the number of rows in a column. It can be used on any data type, including the DATE data type.

Option C) AVG(start_date, end_date) - This option is incorrect because the AVG function is used to calculate the average of numeric values. It cannot be used with multiple columns.

Option D) MIN(start_date) - This option is correct. The MIN function is used to find the minimum value in a column. It can be used on the DATE data type.

Therefore, the two valid aggregate functions on the START_DATE column are COUNT(start_date) and MIN(start_date).

The correct answer is B,D.

In a SELECT statement that includes a WHERE clause, where is the GROUP BY clause placed in the SELECT statement?

technology databases

  1. Immediately after the SELECT clause

  2. After the ORDER BY clause

  3. After the WHERE clause

  4. Before the WHERE clause

Show answer
Correct Option: C

AI Explanation

To answer this question, you need to understand the order in which clauses are typically placed in a SQL SELECT statement.

The correct answer is C) After the WHERE clause.

In a SELECT statement, the WHERE clause is used to filter the rows returned by the query based on a specific condition. The GROUP BY clause, on the other hand, is used to group the rows based on one or more columns.

The typical order of clauses in a SELECT statement is as follows:

  1. SELECT clause
  2. FROM clause
  3. WHERE clause
  4. GROUP BY clause
  5. HAVING clause
  6. ORDER BY clause

Therefore, the GROUP BY clause is placed after the WHERE clause in the SELECT statement. It is used to group the rows after filtering them based on the conditions specified in the WHERE clause.

Which SELECT statement will the result ‘ello world’ from the string ‘Hello World’?

technology databases

  1. SELECT SUBSTR( ‘Hello World’,1) FROM dual;

  2. SELECT INITCAP(TRIM (‘Hello World’, 1,1)) FROM dual;

  3. SELECT LOWER(TRIM (‘H’ FROM ‘Hello World’)) FROM dual;

  4. SELECT LOWER(SUBSTR(‘Hello World’, 2, 1) FROM dual;

Show answer
Correct Option: C
Explanation:

To solve this question, the user needs to know the basic SQL functions and how they can be applied to strings. The user must evaluate each option and determine which one will result in the desired output of 'ello world' from the given string 'Hello World'.

Now, let's go through each option and explain why it is right or wrong:

A. SELECT SUBSTR( ‘Hello World’,1) FROM dual;

This option selects a substring from the given string starting at the first character. Since the starting point is at the first character, the entire string 'Hello World' will be returned. Therefore, this option is incorrect.

B. SELECT INITCAP(TRIM (‘Hello World’, 1,1)) FROM dual;

This option capitalizes the first letter of the given string and removes any leading or trailing spaces. However, the second and third parameters of the TRIM function are invalid and will cause an error. Therefore, this option is also incorrect.

C. SELECT LOWER(TRIM (‘H’ FROM ‘Hello World’)) FROM dual;

This option removes the letter 'H' from the given string, converts it to lowercase, and removes any leading or trailing spaces. The resulting string will be 'ello world', which is the desired output. Therefore, this option is correct.

D. SELECT LOWER(SUBSTR(‘Hello World’, 2, 1) FROM dual;

This option selects a substring from the given string starting at the second character and ending after one character. The resulting substring will be 'e'. This substring is then converted to lowercase. Therefore, this option is incorrect.

The Answer is: C. SELECT LOWER(TRIM (‘H’ FROM ‘Hello World’)) FROM dual;

Which SQL statement generates the alias Annual Salary for the calculated column SALARY*12?
technology databases

  1. SELECT ename, salary*12 ‘Annual Salary’ FROM employees;

  2. SELECT ename, salary*12 “Annual Salary” FROM employees;

  3. SELECT ename, salary*12 AS Annual Salary FROM employees;

  4. SELECT ename, salary*12 AS INITCAP(“ANNUAL SALARY”) FROM employees

Show answer
Correct Option: B

Which clause would you use in a SELECT statement to limit the display to those employees whose salary is greater than 5000?
technology databases

  1. ORDER BY SALARY > 5000

  2. GROUP BY SALARY > 5000

  3. HAVING SALARY > 5000

  4. WHERE SALARY > 5000

Show answer
Correct Option: D

You need to calculate the total of all salaries in the accounting department. Which group function should you use?
technology databases

  1. MAX

  2. MIN

  3. SUM

  4. TOTAL

Show answer
Correct Option: C

Which SELECT statement should you use to extract the year from the system date and display it in the format "1998"?
technology databases

  1. SELECT TO_CHAR(SYSDATE,'yyyy') FROM dual;

  2. SELECT TO_DATE(SYSDATE,'yyyy') FROM dual;

  3. SELECT DECODE(SUBSTR(SYSDATE, 8), 'YYYY') FROM dual;

  4. SELECT DECODE(SUBSTR(SYSDATE, 8), 'year') FROM dual;

Show answer
Correct Option: A
Explanation:

To solve this question, the user needs to know the SQL syntax for extracting specific parts of a date and formatting date values. The user must use the correct function to extract the year from the system date and format it as "1998".

Option A is correct. This option uses the TO_CHAR function to convert the system date to a character string in the format specified by the second argument ('yyyy' in this case). This function extracts the year from the system date and formats it as a 4-digit string. The output will be "1998".

Option B is incorrect. This option uses the TO_DATE function, which is used to convert a character string to a date value. In this case, the first argument is already a date value, so using TO_DATE is unnecessary. Also, the second argument ('yyyy') specifies the format of the output, not the input.

Option C is incorrect. This option uses the DECODE function to extract the year from the system date. However, the syntax is incorrect. DECODE requires at least three arguments: the first is the value to be compared, the second is the comparison value, and the third is the result if the comparison is true. In this case, the first argument (SUBSTR(SYSDATE, 8)) is missing a second argument to compare it to.

Option D is incorrect. This option also uses the DECODE function, but the syntax is incorrect. The SUBSTR function extracts a substring from the system date starting at position 8, which is the day of the month. There is no 'year' substring in this position, so the output will not be correct.

The Answer is: A. SELECT TO_CHAR(SYSDATE,'yyyy') FROM dual;

In which scenario would TOP N analysis be the best solution?
technology databases

  1. You want to identify the most senior employee in the company.

  2. You want to find the manager supervising the largest number of employees

  3. You want to identify the person who makes the highest salary for all employees.

  4. You want to rank the top three sales representatives who have sold the maximum

Show answer
Correct Option: D
Explanation:

To determine the best solution for TOP N analysis, the user must understand what TOP N analysis is and the context in which it can be applied. TOP N analysis is a method of ranking data by selecting the top N items based on a specific criterion. The user should choose option D because it requires identifying the top three sales representatives who have sold the maximum, which is a typical use case for TOP N analysis.

Now, let's go through each option and explain why it is right or wrong:

A. You want to identify the most senior employee in the company. This option is wrong because identifying the most senior employee does not require ranking or selecting the top N employees based on a specific criterion. It only involves identifying one employee based on their seniority level.

B. You want to find the manager supervising the largest number of employees. This option is wrong because finding the manager supervising the largest number of employees does not require ranking or selecting the top N employees based on a specific criterion. It only involves identifying one manager based on the number of employees they supervise.

C. You want to identify the person who makes the highest salary for all employees. This option is wrong because identifying the person who makes the highest salary does not require ranking or selecting the top N employees based on a specific criterion. It only involves identifying one employee based on their salary level.

D. You want to rank the top three sales representatives who have sold the maximum. This option is correct because identifying the top three sales representatives who have sold the maximum requires ranking and selecting the top N employees based on a specific criterion (sales revenue), which is a typical use case for TOP N analysis.

Therefore, the answer is: D.

Evaluate the SQL statement: SELECT ROUND(45.953, -1), TRUNC(45.936, 2) FROM dual; Which values are displayed?
technology databases

  1. 46 and 45

  2. 46 and 45.93

  3. 50 and 45.93

  4. 50 and 45.9

Show answer
Correct Option: C