Andrew and Musa_sql queries_solution

create_schema.sql

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+-- Schema
+DROP TABLE IF EXISTS students;
+CREATE TABLE students (
+  id           serial PRIMARY KEY,
+  first_name   varchar(255) NOT NULL,
+  last_name    varchar(255) NOT NULL,
+  birthdate    date NOT NULL,
+  address_id   integer
+);
+
+DROP TABLE IF EXISTS addresses;
+CREATE TABLE addresses (
+    id           serial PRIMARY KEY,
+    line_1 varchar(255) NOT NULL,
+    city varchar(64) NOT NULL,
+    state varchar(64) NOT NULL,
+    zipcode varchar(64) NOT NULL
+);
+
+DROP TABLE IF EXISTS classes;
+CREATE TABLE classes (
+    id           serial PRIMARY KEY,
+    name varchar(255) NOT NULL,
+    credits varchar(64) NOT NULL
+);
+
+DROP TABLE IF EXISTS enrollments;
+CREATE TABLE enrollments (
+    id           serial PRIMARY KEY,
+    student_id INT NOT NULL,
+    class_id INT NOT NULL,
+    grade varchar(64) 
+);
+
+

seed_data.sql

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+-- Note: We're inserting records with an id value set because we want to use
+-- particular ids as foreign keys. I.e. setting the address_id for a student
+-- so it references a specific address record. If we didn't specify a value
+-- for the id columns, the database would choose an integer for us.
+
+INSERT INTO addresses (id, line_1, city, state, zipcode) VALUES (1, '6232 Guiseppe Courts', 'Jamartown', 'Maryland', '49028');
+INSERT INTO addresses (id, line_1, city, state, zipcode) VALUES (2, '704 Cecil Mountain', 'West Jon', 'South Dakota', '91578');
+INSERT INTO addresses (id, line_1, city, state, zipcode) VALUES (3, '41613 Huel Ranch', 'Loycefort', 'Florida', '12109');
+INSERT INTO addresses (id, line_1, city, state, zipcode) VALUES (4, '1397 Braden Shoals', 'New Karine', 'New York', '03913');
+
+
+INSERT INTO students (id, first_name, last_name, birthdate, address_id) VALUES (1, 'Tianna', 'Lowe', '1985-02-17', 1);
+INSERT INTO students (id, first_name, last_name, birthdate, address_id) VALUES (2, 'Elda', 'Sipes', '1989-08-03', 2);
+INSERT INTO students (id, first_name, last_name, birthdate, address_id) VALUES (3, 'Jed', 'Kunde', '1987-01-22', 3);
+INSERT INTO students (id, first_name, last_name, birthdate, address_id) VALUES (4, 'Leopold', 'Towne', '1984-10-07', NULL);
+INSERT INTO students (id, first_name, last_name, birthdate, address_id) VALUES (5, 'Andre', 'Rohan', '1989-09-01', 4);
+
+INSERT INTO classes (id, name, credits) VALUES (1, 'CS 101', 4);
+INSERT INTO classes (id, name, credits) VALUES (2, 'HIST 107', 3);
+INSERT INTO classes (id, name, credits) VALUES (3, 'SPAN 210', 3);
+INSERT INTO classes (id, name, credits) VALUES (4, 'PHYS 218', 4);
+INSERT INTO classes (id, name, credits) VALUES (5, 'ART 118', 2);
+
+
+-- Tianna took HIST 107 and got a 'B'
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (1, 1, 2, 'B');
+-- Tiana is taking SPAN 210
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (2, 1, 3, NULL);
+-- Elda took ART 118 and got an 'A'
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (3, 2, 5, 'A');
+-- Elda is taking SPAN 210
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (4, 2, 3, NULL);
+-- Elda is taking CS 101
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (5, 2, 1, NULL);
+-- Jed is taking CS 101
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (6, 3, 1, NULL);
+-- Jed is taking HIST 107
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (7, 3, 2, NULL);
+-- Leopold is taking HIST 107
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (8, 4, 2, NULL);
+-- Leopold is taking CS 101
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (9, 4, 1, NULL);
+-- Leopold is taking SPAN 210
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (10, 4, 3, NULL);
+-- Leopold took PHYS 218 and got a 'C'
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (11, 4, 4, 'C');
+-- Leopold took CS 101 and got an 'A'
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (12, 4, 1, 'A');
+-- Andre took CS 101 and got an 'B'
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (13, 5, 1, 'B');
+-- Andre took HIST 107 and got an 'B'
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (14, 5, 2, 'B');
+-- Andre is taking SPAN 210
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (15, 5, 3, NULL);
+-- Andre is taking ART 118
+INSERT INTO enrollments (id, student_id, class_id, grade) VALUES (16, 5, 5, NULL);
+
+-- Because we've inserted rows with hardcoded values for the primary key, id
+-- the sequence used to generate id values for new rows is stuck at "1". So
+-- we manually reset the sequences to the max value of id for each table.
+SELECT setval('addresses_id_seq', (SELECT MAX(id) FROM addresses));
+SELECT setval('students_id_seq', (SELECT MAX(id) FROM students));
+SELECT setval('classes_id_seq', (SELECT MAX(id) FROM classes));
+SELECT setval('enrollments_id_seq', (SELECT MAX(id) FROM enrollments));

statements.sql

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+select * from classes;
+
+select name, credits from classes 
+where credits > '3';
+
+select * from classes
+where mod(credits::int,2) = 0;
+
+
+select first_name, name from enrollments
+join students on enrollments.student_id = students.id
+join classes on enrollments.class_id = classes.id
+where first_name = 'Tianna'
+and grade is null;
+
+select * from students
+where birthdate < '1986-01-01'
+and (first_name ilike '%t%' or last_name ilike '%t%');
+
+select avg(age(birthdate,now())) from students;
+
+select * from addresses
+where city like '% %';
+
+select first_name, last_name, line_1, city,state,zipcode 
+from addresses
+join students on students.address_id=addresses.id
+where city like '% %';
+
+select avg(credits::int) from classes;
+
+select * from enrollments
+join students on enrollments.student_id=students.id
+where grade = 'A';
+
+select first_name, sum(credits::int) from enrollments
+join students on enrollments.student_id=students.id
+join classes on enrollments.class_id = classes.id
+group by first_name;
+
+
+select first_name, sum(credits::int) from enrollments
+join students on enrollments.student_id=students.id
+join classes on enrollments.class_id = classes.id
+where grade is not null
+group by first_name;
+
+select enrollments.*, name from enrollments
+join classes on enrollments.class_id = classes.id;
+
+select * from students
+where birthdate>='1982-01-01'
+and birthdate<='1985-12-31';
+
+insert into enrollments(student_id,class_id,grade)
+values('5','4','A');
+
+select * from enrollments
+join classes on enrollments.class_id = classes.id
+join students on enrollments.student_id=students.id;
+
+