queries.sql

/* Get number of systems programming languages */

SELECT COUNT(*) FROM langs WHERE usage='Системное программирование';

/* Select some data from web dev language entries */

SELECT name, used_paradigm, year FROM langs WHERE usage = 'Веб-разработка';

/* Order results by year (asc order by default) */

SELECT name, year FROM langs ORDER BY year;

/* Pick organisations created before 2000 with revenue of more that 1b$, order by revenue */

SELECT name, revenue, year FROM organisations 
WHERE revenue > 1000000000 AND year < 2000 
ORDER BY revenue DESC;

/* Get organisations with 'Corporation' in the name */

SELECT id, name FROM organisations 
WHERE name LIKE '%Corporation%' 
ORDER BY id;

/* Select languages (without repeats) and corresponding IDEs */

SELECT DISTINCT ON(supported_lang) supported_lang, name 
FROM extra_software WHERE usage='IDE';

/* Select organisation with biggest yearly revenue */

SELECT name, revenue, year FROM organisations 
WHERE revenue = (SELECT MAX(revenue) FROM organisations);

/* Select languages developed by companies with more than 100b$ revenue */

SELECT name, organisation FROM langs 
WHERE organisation IN 
(SELECT name FROM organisations WHERE revenue > 100000000000);

/* Join data of languages (created after 1990) that are main products of companies with company data */

SELECT organisations.name, organisations.revenue, organisations.main_product, langs.year, langs.usage 
FROM organisations JOIN langs ON langs.name = organisations.main_product 
WHERE langs.name IN (SELECT name FROM langs WHERE langs.year > 1990) ORDER BY langs.year DESC;

/* Join names of IDEs and data about their supported langs */

SELECT extra_software.name, langs.name, langs.usage 
FROM langs JOIN extra_software ON extra_software.supported_lang = langs.name 
WHERE extra_software.usage = 'IDE';

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