One of the two uses of -- case is that there is nothing after the case.
SELECT coursename, score, CASE WHEN score<60 THEN 'Failed' WHEN score>=60 AND score<80 THEN '及格' ELSE 'Excellent' END score1 FROM `code_score`
-- another case followed by the column name.
select
case sex
when '1' then 'male'
when '2' then 'female'
else 'eunuch' end
from my_user
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-- Query the names of students with no failing grades. Subquery|distinct function.
SELECT DISTINCT (`name`) FROM my_score WHERE `name` NOT IN (SELECT `name` FROM my_score WHERE score <60)
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