case when

case when a = 1 then b else c when b = 2 then d end

SELECT
    NAME '英雄',
    CASE NAME     //name是和下面when的名字比
        WHEN '德莱文' THEN
            '斧子'
        WHEN '德玛西亚-盖伦' THEN
            '大宝剑'
        WHEN '暗夜猎手-VN' THEN
            '弩'
        ELSE
            '无'
    END '装备'    //装备是这一列的名字
FROM
    user_info;

SELECT
    NAME '英雄',
    age '年龄',
    CASE
        WHEN age < 18 THEN
            '少年'
        WHEN age < 30 THEN
            '青年'
        WHEN age >= 30
        AND age < 50 THEN
            '中年'
        ELSE
            '老年'
    END '状态'
FROM
    user_info;

select cno,count(case when degree>85 and degree <=100 then 1 else 0 end) as "[100-85]" from ...