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प्रश्न
Differentiate between count() and count(*) functions in SQL with appropriate examples.
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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
______ is used to get a specified day of the month for a given date.
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:
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 to display the average marks scored by students of each gender who are in class XI?
(i) Select Gender, avg(Marks) from STUDENT where Class= "XI" group by Gender;
(ii) Select Gender, avg(Marks) from STUDENT group by Gender where Class="XI";
(iii) Select Gender, avg(Marks) group by Gender from STUDENT having Class="XI";
(iv) Select Gender, avg(Marks) from STUDENT group by Gender having Class = "XI";
Choose the correct option:
What will be returned by the given query? Select round(23456.1234, -2) = ______.
What will be returned by the given query? select day of year('2015-02-10') = ______.
What will be returned by the given query? select substr("Computer", 4) = ______.
"COUNT" keyword belongs to which categories in Mysql?
What will be returned by the given query? SELECT DAYOFYEAR('2015-01-10') = ______.
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 name of the functions to perform the following operation:
To display the day like “Monday”, and “Tuesday”, from the date when India got independence.
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 name of the functions to perform the following operation:
To display the name of the month in which you were born.
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 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;
- 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 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’;
Write suitable SQL query for the following:
Display the remainder of 100 divided by 9.
Explain the following SQL function using a suitable example.
UCASE()
Explain the following SQL function using a suitable example.
MID()
Explain the following SQL function using a suitable example.
POWER()
Shreya, a database administrator has designed a database for a clothing shop. Help her by writing answers to the following questions based on the given table:
| TABLE: CLOTH | |||||
| CCODE | CNAME | SIZE | COLOR | PRICE | DOP |
| C001 | JEANS | XL | BLUE | 990 | 2022-01-21 |
| C002 | T-SHIRT | M | RED | 599 | 2021-12-12 |
| C003 | TROUSER | M | GREY | 399 | 2021-11-10 |
| C004 | SAREE | FREE | GREEN | 1299 | 2019-11-12 |
| C005 | KURTI | L | WHITE | 399 | 2021-12-07 |
- Write a query to display cloth names in lowercase.
- Write a query to display the lowest price of the clothes.
- Write a query to count the total number of clothes purchased in medium size.
OR
Write a query to count the year-wise total number of clothes purchased.
