SELECT * FROM pupils WHERE form = '11Б';
{"sename"=>"ЛИСЕНКО", "name"=>"ДМИТРО", "form"=>"11Б", "no"=>"113"}
{"sename"=>"РУДЕНКО", "name"=>"ОЛЕГ", "form"=>"11Б", "no"=>"114"}
{"sename"=>"САВЧЕНКО", "name"=>"ВАЛЕРІЙ", "form"=>"11Б", "no"=>"115"}
{"sename"=>"ПЕТРЕНКО", "name"=>"ЛЕОНІД", "form"=>"11Б", "no"=>"116"}
{"sename"=>"ШУЛЬГА", "name"=>"ГАЛИНА", "form"=>"11Б", "no"=>"117"}
{"sename"=>"РАДЧЕНКО", "name"=>"ТЕТЯНА", "form"=>"11Б", "no"=>"118"}
{"sename"=>"КОРОЛЬ", "name"=>"НАДІЯ", "form"=>"11Б", "no"=>"119"}
{"sename"=>"ОСТАПЕНКО", "name"=>"ЛЮДМИЛА", "form"=>"11Б", "no"=>"120"}

SELECT * FROM classroom WHERE (16 < capacity) and (capacity < 24);
{"building"=>"A", "room_number"=>"1", "capacity"=>21}
{"building"=>"A", "room_number"=>"2", "capacity"=>19}
{"building"=>"A", "room_number"=>"4", "capacity"=>17}

SELECT * FROM classroom WHERE capacity BETWEEN 17 AND 23;
{"building"=>"A", "room_number"=>"1", "capacity"=>21}
{"building"=>"A", "room_number"=>"2", "capacity"=>19}
{"building"=>"A", "room_number"=>"4", "capacity"=>17}

SELECT sename, name FROM pupils WHERE sename LIKE '%УК';
{"sename"=>"КОВАЛЬЧУК", "name"=>"ВІКТОР"}
{"sename"=>"ШЕВЧУК", "name"=>"ПЕТРО"}
{"sename"=>"ПОЛІЩУК", "name"=>"АНДРІЙ"}
{"sename"=>"ТКАЧУК", "name"=>"ГРИГОРІЙ"}

SELECT sename, name FROM pupils WHERE name IN ( 'АНДРІЙ', 'ГРИГОРІЙ');
{"sename"=>"ПОЛІЩУК", "name"=>"АНДРІЙ"}
{"sename"=>"ТКАЧУК", "name"=>"ГРИГОРІЙ"}

SELECT COUNT(*) FROM pupils;
{"COUNT(*)"=>32}

SELECT quality, COUNT(no) FROM teachers GROUP BY quality;
{"quality"=>"I категорія", "COUNT(no)"=>2}
{"quality"=>"II категорія", "COUNT(no)"=>2}
{"quality"=>"вища категорія", "COUNT(no)"=>2}
{"quality"=>"вчитель-методист", "COUNT(no)"=>1}
{"quality"=>"спеціаліст", "COUNT(no)"=>1}

SELECT quality, COUNT(no) FROM teachers GROUP BY quality HAVING COUNT(no) > 1;
{"quality"=>"I категорія", "COUNT(no)"=>2}
{"quality"=>"II категорія", "COUNT(no)"=>2}
{"quality"=>"вища категорія", "COUNT(no)"=>2}

SELECT sename,mark FROM marks WHERE (day='2020-09-24') ORDER BY mark;
{"sename"=>"ШЕВЧУК", "mark"=>6}
{"sename"=>"КОВАЛЬ", "mark"=>7}
{"sename"=>"БОНДАРЕНКО", "mark"=>8}
{"sename"=>"ПОЛІЩУК", "mark"=>8}
{"sename"=>"ТКАЧЕНКО", "mark"=>9}
{"sename"=>"ОЛІЙНИК", "mark"=>10}
{"sename"=>"КРАВЧЕНКО", "mark"=>11}
{"sename"=>"КОВАЛЬЧУК", "mark"=>12}

SELECT sename,mark FROM marks WHERE (day='2020-09-24') ORDER BY mark DESC;
{"sename"=>"КОВАЛЬЧУК", "mark"=>12}
{"sename"=>"КРАВЧЕНКО", "mark"=>11}
{"sename"=>"ОЛІЙНИК", "mark"=>10}
{"sename"=>"ТКАЧЕНКО", "mark"=>9}
{"sename"=>"БОНДАРЕНКО", "mark"=>8}
{"sename"=>"ПОЛІЩУК", "mark"=>8}
{"sename"=>"КОВАЛЬ", "mark"=>7}
{"sename"=>"ШЕВЧУК", "mark"=>6}

SELECT sename AS 'Прізвище',mark AS 'Оцінка' FROM marks WHERE (day='2020-09-24') ORDER BY mark DESC LIMIT 3,3;
{"Прізвище"=>"ТКАЧЕНКО", "Оцінка"=>9}
{"Прізвище"=>"БОНДАРЕНКО", "Оцінка"=>8}
{"Прізвище"=>"ПОЛІЩУК", "Оцінка"=>8}

SELECT * FROM courses JOIN department ON courses.dept_name = department.dept_name;
{"title"=>"алгебра", "form"=>"10A", "no"=>nil, "hours"=>5, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"алгебра", "form"=>"10Б", "no"=>nil, "hours"=>5, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"алгебра", "form"=>"11A", "no"=>nil, "hours"=>5, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"алгебра", "form"=>"11Б", "no"=>nil, "hours"=>5, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"геометрія", "form"=>"10A", "no"=>nil, "hours"=>3, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"геометрія", "form"=>"10Б", "no"=>nil, "hours"=>3, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"геометрія", "form"=>"11A", "no"=>nil, "hours"=>3, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"геометрія", "form"=>"11Б", "no"=>nil, "hours"=>3, "dept_name"=>"математики", "persons"=>nil}

SELECT * FROM courses LEFT OUTER JOIN department ON courses.dept_name = department.dept_name;
{"title"=>"алгебра", "form"=>"10A", "no"=>nil, "hours"=>5, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"алгебра", "form"=>"10Б", "no"=>nil, "hours"=>5, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"алгебра", "form"=>"11A", "no"=>nil, "hours"=>5, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"алгебра", "form"=>"11Б", "no"=>nil, "hours"=>5, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"біологія", "form"=>"11А", "no"=>nil, "hours"=>2, "dept_name"=>nil, "persons"=>nil}
{"title"=>"геометрія", "form"=>"10A", "no"=>nil, "hours"=>3, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"геометрія", "form"=>"10Б", "no"=>nil, "hours"=>3, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"геометрія", "form"=>"11A", "no"=>nil, "hours"=>3, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"геометрія", "form"=>"11Б", "no"=>nil, "hours"=>3, "dept_name"=>"математики", "persons"=>nil}

SELECT * FROM courses RIGHT OUTER JOIN department ON courses.dept_name = department.dept_name;
{"title"=>"алгебра", "form"=>"10A", "no"=>nil, "hours"=>5, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"алгебра", "form"=>"10Б", "no"=>nil, "hours"=>5, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"алгебра", "form"=>"11A", "no"=>nil, "hours"=>5, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"алгебра", "form"=>"11Б", "no"=>nil, "hours"=>5, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"геометрія", "form"=>"10A", "no"=>nil, "hours"=>3, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"геометрія", "form"=>"10Б", "no"=>nil, "hours"=>3, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"геометрія", "form"=>"11A", "no"=>nil, "hours"=>3, "dept_name"=>"математики", "persons"=>nil}
{"title"=>"геометрія", "form"=>"11Б", "no"=>nil, "hours"=>3, "dept_name"=>"математики", "persons"=>nil}
{"title"=>nil, "form"=>nil, "no"=>nil, "hours"=>nil, "dept_name"=>"інформатики", "persons"=>nil}
{"title"=>nil, "form"=>nil, "no"=>nil, "hours"=>nil, "dept_name"=>"фізики", "persons"=>nil}
{"title"=>nil, "form"=>nil, "no"=>nil, "hours"=>nil, "dept_name"=>"хіміки", "persons"=>nil}