Advertisements
Advertisements
Question
Differentiate between count() and count(*) functions in SQL with appropriate examples.
Advertisements
Solution
COUNT(*) returns the count of all rows in the table, whereas COUNT() is used with Column_Name passed as an argument and counts the number of non-NULL values in a column that is given as an argument.
Example: Table: EMPL
| EMPNO | ENAME | JOB | SAL | DEPTNO |
| 8270 | JACK | SALESMAN | 2985 | 10 |
| 8566 | ALI | CLERK | 9870 | 20 |
| 8922 | AJAY | NULL | 8760 | 30 |
| 8736 | BINDU | CLERK | 5643 | 20 |
| 8822 | JOY | MANAGER | 3000 | 10 |
e.g. SELECT COUNT(*) FROM EMPL;
Output
| COUNT(*) |
| 5 |
e.g. SELECT COUNT(JOB) FROM EMPL;
Output
| COUNT(JOB) |
| 4 |
Since JOB has 1 NULL value.
APPEARS IN
RELATED QUESTIONS
______ is used to get a specified day of the month for a given date.
______ keyword is used to find out the number of values in a column?
Which method is used to get the row-id of the last modified row?
The MAX () function finds the
Which of the following is not an aggregate function?
What will be returned by the given query? Select round(23456.1234, -2) = ______.
What will be returned by the given query? select power(3, 2) = ______.
What will be returned by the given query? Select length(trim("ABC Public School")) = ______.
What will be returned by the given query? SELECT MID('LeaminglsFun', 2, 4) = ______.
What is the general format of UPPER() return type?
Which statement is used to count the number of rows in table?
Site any two differences between Single Row Functions and Aggregate Functions.
Write the output produced by the following SQL statement:
SELECT LENGTH("Informatics Practices");
Which function is used to display the total number of records from a table in a database?
Write the outputs of the SQL queries based on the relations Teacher and Placement given below:
Table: Teacher
| T_ID | Name | Age | Department | Date_of_join | Salary | Gender |
| 1 | Arunan | 34 | Computer Sc | 2019-01-10 | 12000 | M |
| 2 | Saman | 31 | History | 2017-03-24 | 20000 | F |
| 3 | Randeep | 32 | Mathematics | 2020-12-12 | 30000 | M |
| 4 | Samira | 35 | History | 2018-07-01 | 40000 | F |
| 5 | Raman | 42 | Mathematics | 2021-09-05 | 25000 | M |
| 6 | Shyam | 50 | History | 2019-06-27 | 30000 | M |
| 7 | Shiv | 44 | Computer Sc | 2019-02-25 | 21000 | M |
| 8 | Shalakha | 33 | Mathematics | 2018-07-31 | 20000 | F |
Table: Placement
| P_ID | Department | Place |
| 1 | History | Ahmedabad |
| 2 | Mathematics | Jaipur |
| 3 | Computer Sc | Nagpur |
- SELECT Department, avg(salary) FROM Teacher GROUP BY Department;
- SELECT MAX(Date_of_Join), MIN(Date_of_Join) FROM Teacher;
- SELECT Name, Salary, T.Department, Place FROM Teacher T, Placement P WHERE T.Department = P.Department AND Salary>20000;
- SELECT Name, Place FROM Teacher T, Placement P WHERE Gender = ’F’ AND T.Department = P.Department;
Predict the output of the code given below:
s="welcome2cs"
n = len(s)
m=""
for i in range(0, n):
if (s[i] >= 'a' and s[i] <= 'm'):
m = m +s[i].upper()
elif (s[i] >= 'n' and s[i] <= 'z'):
m = m +s[i-1]
elif (s[i].isupper()):
m = m + s[i].lower()
else:
m = m +'&'
print(m)Which one of the following is not an aggregate function?
Which one of the following functions are used to find the largest value from the given data in MySQL?
In SQL, which function is used to display the current date and time?
Write outputs for SQL queries that are based on the given table PURCHASE:
| TABLE: PURCHASE | ||||
| CNO | CNAME | CITY | QUANTITY | DOP |
| C01 | GURPREET | NEW DELHI | 150 | 2022-06-11 |
| C02 | MALIKA | HYDERABAD | 10 | 2022-02-19 |
| C03 | NADAR | DALHOUSIE | 100 | 2021-12-04 |
| C04 | SAHIB | CHANDIGARH | 50 | 2021-10-10 |
| C05 | MEHAK | CHANDIGARH | 15 | 2021-10-20 |
- SELECT LENGTH(CNAME) FROM PURCHASE WHERE QUANTITY>100;
- SELECT CNAME FROM PURCHASE WHERE MONTH(DOP) = 3;
- SELECT MOD (QUANTITY, DAY(DOP)) FROM PURCHASE WHERE CITY = ‘CHANDIGARH’;
Based on the table STUDENT given here, write suitable SQL queries for the following:
| Roll No | Name | Class | Gender | City | Marks |
| 1 | Abhishek | XI | M | Agra | 430 |
| 2 | Prateek | XII | M | Mumbai | 440 |
| 3 | Sneha | XI | F | Agra | 470 |
| 4 | Nancy | XII | F | Mumbai | 492 |
| 5 | Himanshu | XII | M | Delhi | 360 |
| 6 | Anchal | XI | F | Dubai | 256 |
| 7 | Mehar | X | F | Moscow | 324 |
| 8 | Nishant | X | M | Moscow | 429 |
- Display gender-wise highest marks.
- Display city-wise lowest marks.
- Display the total number of male and female students.
Explain the following SQL function using a suitable example.
POWER()
Which function returns the sum of all elements of a list?
