MySQL Multiple Choice Questions on “The group by & having Clause”.
1. What is the meaning of “GROUP BY” clause in Mysql?
a) Group data by column values
b) Group data by row values
c) Group data by column and row values
d) None of the mentioned
Answer: a
Clarification: None.
2. Which clause is similar to “HAVING” clause in Mysql?
a) SELECT
b) WHERE
c) FROM
d) None of the mentioned
Answer: b
Clarification: “WHERE” is also used to filter the row values in Mysql.
3. What is the meaning of “HAVING” clause in Mysql?
a) To filter out the row values
b) To filter out the column values
c) To filter out the row and column values
d) None of the mentioned
Answer: a
Clarification: None.
4. “COUNT” keyword belongs to which categories in Mysql?
a) Aggregate functions
b) Operators
c) Clauses
d) All of the mentioned
Answer: a
Clarification: None.
5. Which among the following belongs to an “aggregate function”?
a) COUNT
b) UPPER
c) LOWER
d) All of the mentioned
Answer: a
Clarification: None.
6. Which of the following belongs to an “aggregate function”?
a) COUNT
b) SUM/AVG
c) MIN/MAX
d) All of the mentioned
Answer: d
Clarification: None.
7. Which clause is used with an “aggregate functions”?
a) GROUP BY
b) SELECT
c) WHERE
d) Both GROUP BY and WHERE
Answer: a
Clarification: “GROUP BY” is used with aggregate functions.
8. What is the significance of the statement “GROUP BY d.name” in the following MySQL statement?
SELECT d.name, COUNT (emp_id) emp_no FROM department d INNER JOIN Employee e ON d.dept_id=e.emp_id GROUP BY d.name
a) Aggregation of the field “name” of both table
b) Aggregation of the field “name” of table “department”
c) Sorting of the field “name”
d) None of the mentioned
Answer: b
Clarification: “GROUP BY” clause s used for aggregation of field.
9. What is the significance of the statement “HAVING COUNT (emp_id)>2” in the following MySQL statement?
SELECT d.name, COUNT (emp_id) emp_no FROM department d INNER JOIN Employee e ON d.dept_id=e.emp_id GROUP BY d.name HAVING COUNT (emp_id)>2
a) Filter out all rows whose total emp_id below 2
b) Selecting those rows whose total emp_id>2
c) Filter out all rows whose total emp_id below 2 & Selecting those rows whose total emp_id>2
d) None of the mentioned
Answer: c
Clarification: “HAVING” clause are worked similar as “WHERE” clause.