Question

SQL FORMAT (1-3 and 11-13 are completed and correct)

-- 1. what is the average age of people from China?
select avg(age) from census where native_country ='China';

-- 2. what is the average age of people from Taiwan?
select avg(age) from census where native_country = ‘Taiwan’;

-- 3. which native countries have "land" in their name?
select distinct(native_country) from census where native_country like '%land$

-- 4. what values of the attribute 'marital_status' appear in the data set? Don't show duplicates.

-- 5. what is the average hours per week of work for people from France between 18 and 25? (inclusive)

-- 6. which people (show all columns) are from Laos, Cuba, or Peru? Show only 10 lines.

-- 7. what is the average education years for people having a native country that is not the US?

-- 8. how many executive managers in the data set?

-- 9. how many executive managers have more than 12 years of education?

-- 10. how many different native countries are found in the data set?

-- 11. what are the names of all students who have taken some course? Don't show duplicates.
select distinct(name) from student where tot_cred > 0;

-- 12. what are the names of departments that offer 4-credit courses? Don't list duplicates.
select distinct(dept_name) from course where credits=4;

-- 13. What are the names and IDs of all students who have received an A in a computer science class?
select distinct(name), id from student natural join takes natural join cours$

-- 14. How many B grades have been given to physics majors?

-- 15. What is the average total credits of students who have taken CS-319?

-- 16. What is the average total credits of students who have taken CS-101?

-- 17. What are the course IDs of courses taught by instructor Katz?

-- 18. What are the course IDs of all courses offered by instructor Crick's department?

-- 19. What is the course_id, semester, and year of sections of computer science courses?
-- Don't show duplicates.

-- 20. What are the names of students who have taken a class taught by instructor Srinivasan?

Answer 1

4. 
select distinct(marital_status)
from census;

5.
select avg(hours_per_week)
from census
where native_country='France'
and age>17
and age<26;

6.
select *
from census
where native_country='Laos'
or native_country='Cuba'
or native_country='Peru'
limit=10;

7.
select avg(edu_years)
from census
where not native_country='US';

8.
select count(*)
from census
where designation='executive manager';

9.
select count(*)
from census
where designation='executive manager'
and edu_years>12;

10.
select count (distinct native_country)
from census;

Post rest of the questions separately.