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प्रश्न
Differentiate between count() and count(*) functions in SQL with appropriate examples.
उत्तर
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
संबंधित प्रश्न
______ 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?
Which of the following belongs to an "aggregate function"?
Consider the table STUDENT given below:
| RollNo | Name | Class | DOB | Gender | City | Marks |
| 1 | Anand | XI | 6/6/97 | M | Agra | 430 |
| 2 | Chetan | XII | 7/5/94 | M | Mumbai | 460 |
| 3 | Geet | XI | 6/5/97 | F | Agra | 470 |
| 4 | Preeti | XII | 8/8/95 | F | Mumbai | 492 |
| 5 | Saniyal | XII | 8/10/95 | M | Delhi | 360 |
| 6 | Maakhiy | XI | 12/12/94 | F | Dubai | 256 |
| 7 | Neha | X | 8/12/95 | F | Moscow | 324 |
| 8 | Nishant | X | 12/6/95 | M | Moscow | 429 |
State the command that will give the output as:
| Name |
| Anand |
| Chetan |
| Geet |
| Preeti |
(i) select Name from student where Class ='XI' and Class='XII';
(ii) select name from student where not Class='XI' and Class='XII';
(iii) select name from student where City="Agra" or City="Mumbai";
(iv) select name from student where City in("Agra", "Mumbai");
Choose the correct option:
What will be the output of the following SQL statement?
SELECT DAY NAME (2022-04-08)
Assertion (A): COUNf function ignores DISTINCT
Reason (R): DISTINCT ignores the duplicate values.
Which of the following is not an aggregate function?
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What will be returned by the given query? SELECT MID('LeaminglsFun', 2, 4) = ______.
Name a function of MySQL which is used to remove trailing and leading spaces from a string.
"COUNT" keyword belongs to which categories in Mysql?
Name a function of MySQL used to give position of the first occurrence of a string2 in string1.
What will be returned by the given query? SELECT INSTR('INFORMATIONFORM', 'FOR') = ______.
Which of the following is not a date function?
Which of the following is not a text function?
What is the general format of UPPER() return type?
Site any two differences between Single Row Functions and Aggregate Functions.
Write the name of the functions to perform the following operation:
To display the specified number of characters from a particular position of the given string.
Write the output produced by the following SQL statement:
SELECT ROUND(342.9234, -1);
Write the output produced by the following SQL statement:
SELECT LENGTH("Informatics Practices");
Write the output produced by the following SQL statement:
SELECT YEAR(“1979/11/26”),
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Write the output produced by the following SQL statement:
SELECT LEFT("INDIA", 3), RIGHT("Computer Science", 4), MID("Informatics", 3, 4), SUBSTR("Practices", 3);
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;
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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 +'&'
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SELECT COUNT(column name) FROM inventory;
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Which one of the following is not an aggregate function?
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In SQL, which function is used to display the current date and time?
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.
Write suitable SQL query for the following:
Display the position of occurrence of the string ‘COME’ in the string ‘WELCOME WORLD’.
Write suitable SQL query for the following:
Round off the value 23.78 to one decimal place.
Write suitable SQL query for the following:
Display the remainder of 100 divided by 9.
Explain the following SQL function using a suitable example.
TRIM()
Which function returns the sum of all elements of a list?
