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Q1. Indicate the number of rows and the information provided by
each of the queries below:SELECT ci.name, ci.district,
ci.population FROM city ci
WHERE ci.population < all (SELECT country.population
FROM country
WHERE continent = 'europe');
SELECT ci.name, ci.district, ci.population FROM city ci
WHERE ci.population >ANY(SELECT country.population
FROM country
WHERE continent = 'europe');SELECT ci.name, ci.district,
ci.population FROM city ci
WHERE ci.population IN(SELECT MIN(country.population)
FROM country GROUP BY region);
SELECT ci.name, ci.district, ci.population FROM city ci
WHERE ci.population > ALL (SELECT MIN(country.population)
FROM country GROUP BY region);
SELECT ci.name, ci.district, ci.population FROM city ci
WHERE ci.population NOT IN (SELECT MIN(country.population)
FROM country GROUP BY region);
Q2. Provide the SQL statement to list all non-European countries
whose life expectancies are less thanall maximum life expectancies
of all European regions.
Heading: Country, LifeExpectancyResult: 98 rows (1st row:
Afghanistan, 45.9 )Required: 5th row
Q3. Provide the SQL statement to list the maximum populations in
each region. Filter the results suchthat only regions with maximum
populations that exceed all the lowest populations in
Europeanregions are shown.
Heading: Region, Maximum PopulationResult: 20 rows (1st row:
Australia and New Zealand, 18886000)
Required: 3rd row
Database Management Systems Laboratory Activity #4b
During this activity, you should:
enhance your previous knowledge on using subqueries in SQL
SELECT statements apply the use of subqueries in SQL SELECT
statements, specifically in theWHERE and HAVING clauses distinguish
between single-row subqueries and multiple-row subqueries
More concepts on subqueries:1. Multiple-row subqueries are
expected to return more than one row and are used with the IN,ANY
(works in the
same way as SOME) orALL operators. TheNOT operator can be used
with the IN,ANY, andALL operators.
When using SOME orANY, use the DISTINCT keyword to prevent rows
from appearing several times.
>ALL means more than the maximum value returned by the
subquery
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Q4. Provide the SQL statement to list all countries that speak
any of the languages of Madagascar.Madagascar should not be
included in the list.
Heading: country, language, region
Result: 26 rows (1st row: Andorra, French, Southern
Europe)Required: 3rd row (country, language)
Q5. Modify the query above so that only the countries are
displayed. Each country in the resultshould appear only once.
Heading: CountryResult: 25 rowsRe uired: 16th row
2. Some seemingly correct queries may not return the correct
results. If the subquery returns no rows, the main querywill return
no rows.
Q6. Analyze the query below and indicate the information that it
is intended to provide. Why does itnot return any rows?SELECT name,
continent, region
FROM country
WHERE region = (SELECT region FROM country
WHERE name = 'Russia');
Q7. The query below correctly displays all capital cities.
Indicate the number of rows returned by thequery.SELECT ci.id,
ci.name
FROM city ci
WHERE ci.id IN (SELECT capital FROM country);
Q8. Suppose, it is required to display all cities that are not
capitals. The first query below seems to bea logical solution.
However the second query provides the correct information. Indicate
thenumber of rows returned by each query and explain the error in
the f irst statement.
a) SELECT ci.id, ci.nameFROM city ci
WHERE ci.id NOT IN (SELECT capital FROM country);
b) SELECT ci.id, ci.name FROM city ciWHERE ci.id NOT IN (SELECT
capital FROM country)
WHERE capital IS NOT NULL);;
Q9. Provide the SQL statement to list all all countries in Asia
whose year of independence does notmatch any of the years of
independence of countries in Africa.
Heading: Country, Independence Year
Result: 40 rows (2nd row: United Arab Emirates, 1971)
Required: 5
th
row
