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Practice Problems - Mixed-up Code

Now, let’s spend 15 minutes to practice what we just learned!

Please do not refer back to the previous page or outside resources.

You can stop working on a problem after you worked on it for about three minutes without solving it.

Problems

In the grades table:

Please write a SELECT statement to retrieve the student_id, test_name, and english of all entries whose english is lower than 60 and math is higher than 90.

--hiddenprefix-- DROP TABLE IF EXISTS grades; create table "grades" ("student_id" INTEGER, "test_name" TEXT, "english" INTEGER, "math" INTEGER); INSERT INTO grades (student_id,test_name,english,math) VALUES ('1', 'midterm', 62, 84), ('1', 'final', 70, 86), ('2', 'midterm', 50, 95), ('2', 'final', 80, 99), ('3', 'midterm', 55, 91); --blocks-- SELECT student_id, test_name, english FROM grades WHERE english < 60 AND math > 90 english < 60 & math > 90 --unittest-- assert 0,0 == 2 assert 0,1 == midterm assert 1,0 == 3 assert 1,1 == midterm

In the grades table:

A student completed an extra assignment and got some additional points.

Please write an UPDATE statement to change the entry whose student_id is 1, and set their math score to 90 in the final test (test_name column).

--hiddenprefix-- DROP TABLE IF EXISTS grades; create table "grades" ("student_id" INTEGER, "test_name" TEXT, "english" INTEGER, "math" INTEGER); INSERT INTO grades (student_id,test_name,english,math) VALUES ('1', 'midterm', 62, 84), ('1', 'final', 70, 86), ('2', 'midterm', 50, 95), ('2', 'final', 80, 99), ('3', 'midterm', 55, 91); --blocks-- UPDATE grades SET math = 90 WHERE student_id = 1 AND test_name = "final" LET student_id = 1 AND test_name = final --hiddensuffix-- SELECT * FROM grades; --unittest-- assert 1,1 == final assert 1,3 == 90 assert 3,3 == 99

In the grades table:

The instructors decided to add some points to all students as one test was too difficult.

Please write an UPDATE statement to change all entries whose test_name is midterm, and add 10 points to their english score.

--hiddenprefix-- DROP TABLE IF EXISTS grades; create table "grades" ("student_id" INTEGER, "test_name" TEXT, "english" INTEGER, "math" INTEGER); INSERT INTO grades (student_id,test_name,english,math) VALUES ('1', 'midterm', 62, 84), ('1', 'final', 70, 86), ('2', 'midterm', 50, 95), ('2', 'final', 80, 99), ('3', 'midterm', 55, 91); --blocks-- UPDATE grades SET english = english + 10 WHERE test_name = "midterm" english + 10 --hiddensuffix-- SELECT * FROM grades --unittest-- assert 0,2 == 72 assert 1,2 == 70 assert 2,2 == 60 assert 3,2 == 80 assert 4,2 == 65

Aside from the grades table:

We also have a students table:

Now we want to match the student name to their math grades.

Please write a statement using SELECT and JOIN to: select the test_name and math from the grades table and name from the students table, where the student_id in the grades table is the same as the id in the students table.

--hiddenprefix-- DROP TABLE IF EXISTS grades; create table "grades" ("student_id" INTEGER, "test_name" TEXT, "english" INTEGER, "math" INTEGER); INSERT INTO grades (student_id,test_name,english,math) VALUES ('1', 'midterm', 62, 84), ('1', 'final', 70, 86), ('2', 'midterm', 50, 95), ('2', 'final', 80, 99), ('3', 'midterm', 55, 91); DROP TABLE IF EXISTS students; create table "students" ("id" INTEGER, "name" TEXT); INSERT INTO students (id,name) VALUES (1, 'Alex'), (2, 'Blake'), (3, 'Charlie'); --blocks-- SELECT grades.test_name, grades.math, students.name FROM grades JOIN students ON students.id = grades.student_id ON students.id = grades.id --unittest-- assert 0,2 == Alex assert 3,2 == Blake

Aside from the grades table:

We also have a tests table:

Now we want to add the date information to the grades to see when the students took the tests.

Please write a statement using SELECT and JOIN to: select the date and name from the tests table and student_id from the grades table, where the test_name in the grades table is the same as the name in the tests table.

--hiddenprefix-- DROP TABLE IF EXISTS grades; create table "grades" ("student_id" INTEGER, "test_name" TEXT, "english" INTEGER, "math" INTEGER); INSERT INTO grades (student_id,test_name,english,math) VALUES ('1', 'midterm', 62, 84), ('1', 'final', 70, 86), ('2', 'midterm', 50, 95), ('2', 'final', 80, 99), ('3', 'midterm', 55, 91); DROP TABLE IF EXISTS tests; create table "tests" ("name" TEXT, "date" DATE); INSERT INTO tests (name,date) VALUES ('midterm', '2022-10-15'), ('final', '2022-11-13'); --blocks-- SELECT tests.date, tests.name, grades.student_id FROM tests JOIN grades ON grades.test_name = tests.name --unittest-- assert 0,0 == 2022-10-15 assert 0,1 == midterm assert 0,2 == 1

What to do next

Click on the following link to go to the post test: Post Test

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