您需要再次使用魔术词和 p>

You need to use the magic word and again:

CREATE TABLE students (
....
 , CONSTRAINT IC4 CHECK ( classification = 'junior' AND hours >=55 AND hours <= 84 ) 

我怀疑你会想要其他分类（和使用BETWEEN来定义范围的清晰度）....

I suspect you'll want to have other classifications too, and validate their ranges. Use parentheses and OR to do this. (And use BETWEEN to define the ranges for clarity)....

, CONSTRAINT IC4 CHECK ( ( classification = 'junior' AND hours BETWEEN 55 AND 84 ) 
                       OR ( classification = 'sophomore' AND hours BETWEEN 85 AND 124 )  
                       OR ( classification = 'senior' AND hours > 124 )  
                       OR ( classification = 'fresher' )
                       )                                 

请确保您有一套完整的范围。

Make sure you have a complete set of ranges.