在SELECT语句中使用CASE- when -THEN时，如何在MySQL中进行搜索？

SELECT column1, column2, 
    CASE 
        WHEN condition1 THEN result1
        WHEN condition2 THEN result2
        ELSE result3
    END AS result_column
FROM table_name
WHERE condition;

CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    ...
    ELSE resultN
END

SELECT student_name, score,
    CASE
        WHEN score >= 90 THEN 'A'
        WHEN score >= 80 THEN 'B'
        WHEN score >= 70 THEN 'C'
        WHEN score >= 60 THEN 'D'
        ELSE 'F'
    END AS grade
FROM students;