Here is the requirement:

The goal is a table that shows how many students have earned which letter_grade. You can output the letter_grade by using CASE with the number_grade column, outputting ‘A’ for grades > 90, ‘B’ for grades > 80, ‘C’ for grades > 70, and ‘F’ otherwise. Then you can use COUNT with GROUP BY to show the number of students with each of those grades.

```
CREATE TABLE student_grades (
id INTEGER PRIMARY KEY AUTOINCREMENT,
name TEXT,
number_grade INTEGER,
fraction_completed REAL);
INSERT INTO student_grades (name, number_grade, fraction_completed)
VALUES ("Winston", 90, 0.805);
INSERT INTO student_grades (name, number_grade, fraction_completed)
VALUES ("Winnefer", 95, 0.901);
INSERT INTO student_grades (name, number_grade, fraction_completed)
VALUES ("Winsteen", 85, 0.906);
INSERT INTO student_grades (name, number_grade, fraction_completed)
VALUES ("Wincifer", 66, 0.7054);
INSERT INTO student_grades (name, number_grade, fraction_completed)
VALUES ("Winster", 76, 0.5013);
INSERT INTO student_grades (name, number_grade, fraction_completed)
VALUES ("Winstonia", 82, 0.9045);
SELECT name,number_grade,round(fraction_completed*100) AS percent_completed FROM student_grades;
/*this part*/
SELECT COUNT(*),
CASE
WHEN number_grade> 90
THEN "A"
WHEN number_grade> 80
THEN "B"
WHEN number_grade> 70
THEN "C"
ELSE
"F"
END as "letter_grade"
FROM student_grades;
```

What i get is this: 6 students all have the grade B.,…

What went wrong?