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  • MySQL case

    /*创建表c1*/
    
    CREATE TABLE c1 (
        id INT,
        sex VARCHAR (10),
        score INT
    );
    
    /*插入数据*/
    INSERT INTO  c1
    VALUES
        (1001, '' ,65),
        (1002, '' ,75),
        (1003, '' ,82),
        (1004, '' ,70),
        (1005, '' ,89),
        (1006, '' ,90),
        (1007, '' ,85);
    
    SELECT * FROM c1;

    /*将性别男、女分别用0、1替换*/
    
    SELECT
        id,
        CASE 
            WHEN sex = '' THEN 0
            WHEN sex = '' THEN 1 END sex ,
        score
    FROM c1;

     

    /*将成绩分为小于60 差,60~80 中,80~90良,90以上优*/
    
    SELECT * ,
        CASE 
            WHEN score<60 THEN ''
            WHEN score>=60 AND score<80 THEN ''
            WHEN score>=80 AND score<90 THEN ''
            WHEN score>=90  THEN '' END level
    FROM c1;

     

    /*将成绩等级分为四列*/
    SELECT id, sex,score,
        CASE  WHEN score<60 THEN '' END AS level1,
        CASE  WHEN score>=60 AND score<80 THEN '' END AS level2,
        CASE  WHEN score>=80 AND score<90 THEN '' END AS level3,
        CASE  WHEN score>=90  THEN ''END  AS level4
    FROM c1;

     

    /*按照性别计算各成绩等级中的数量*/
    
    SELECT sex,
        SUM(CASE WHEN score<60 THEN 1 ELSE 0 END) AS '',
        SUM(CASE WHEN score>=60 AND score<80 THEN 1 ELSE 0 END) AS '',
        SUM(CASE WHEN score>=80 AND score<90 THEN 1 ELSE 0 END) AS '',
        SUM(CASE WHEN score>=90 THEN 1 ELSE 0 END) AS ''
    FROM c1
    GROUP BY sex;

     

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  • 原文地址:https://www.cnblogs.com/niniya/p/9033425.html
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