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提交日期 题目名称 提交代码
2024-11-29 人数最多的学生姓氏 
select left(name, 1) AS surname,
    COUNT(*) AS cnt
from students 
GROUP BY LEFT(name, 1)
ORDER BY cnt DESC
limit 5
2024-11-29 学生信息和班主任姓名 
SELECT 
st.name,
st.class_code,
st.grade_code,
t.name AS head_teacher_name
FROM 
students st
JOIN 
teachers t ON st.class_code = t.head_teacher
ORDER BY 
st.student_id;
2024-11-29 学生信息和班主任姓名 
SELECT 
st.name,
st.class_code,
st.grade_code,
t.name AS head_teacher_name
FROM 
students st
JOIN 
teachers t ON st.class_code = t.class_code
ORDER BY 
st.student_id;
2024-11-29 学生信息和班主任姓名 
SELECT 
st.name,
st.class_code,
st.grade_code,
t.name AS head_teacher_name
FROM 
students st
JOIN 
scores sc ON st.student_id = sc.student_id
JOIN 
teachers t ON sc.subject = t.subject
ORDER BY 
st.student_id;
2024-11-25 分组与聚合函数(3)五花八门的项目,其实都有固定套路(1) 
select trx_amt,count(mch_nm) as trx_cnt 
from cmb_usr_trx_rcd
where mch_nm = '红玫瑰按摩保健休闲'
and year(trx_time) = 2024
and month(trx_time) in (1, 2, 3, 4, 5, 6, 7)
group by trx_amt
order by trx_cnt desc
limit 5
2024-11-25 分组与聚合函数(2)擦边营收怎么样,聚合函数可看出 
select date(trx_time) as trx_date,max(trx_amt) as max_trx_amt,min(trx_amt) as min_trx_amt,avg(trx_amt) as avg_trx_amt,sum(trx_amt) as total_trx_amt
from cmb_usr_trx_rcd
where mch_nm='红玫瑰按摩保健休闲'
and date(trx_time) between '2024-09-01' and '2024-09-30'
group by date(trx_time)
order by date(trx_time)
2024-11-25 分组与聚合函数(2)擦边营收怎么样,聚合函数可看出 
select date(trx_time) as trx_date,max(trx_amt) as max_trx_amt,min(trx_amt) as min_trx_amt,avg(trx_amt) as avg_trx_amt,sum(trx_amt) as total_trx_amt
from cmb_usr_trx_rcd
where mch_nm='红玫瑰按摩保健休闲'
and date(trx_time) between '2024-09-01' and '2023-09-30'
group by date(trx_time)
order by date(trx_time)
2024-11-25 分组与聚合函数(2)擦边营收怎么样,聚合函数可看出 
select date(trx_time) as trx_date,max(trx_amt) as max_trx_amt,min(trx_amt) as min_trx_amt,avg(trx_amt) as avg_trx_amt,sum(trx_amt) as total_trx_amt
from cmb_usr_trx_rcd
where mch_nm='红玫瑰按摩保健休闲'
and date(trx_time) between '2024-09-01' and '2023-09-30'
group by date(trx_time)
order by trx_date
2024-11-25 分组与聚合函数(1)Money全都花在哪,GroupBy来查一查 
select mch_nm,sum(trx_amt) as sum_trx_amt 
from cmb_usr_trx_rcd
where year(trx_time)=2024 and usr_id='5201314520'
group by mch_nm
order by sum_trx_amt desc
2024-11-25 条件过滤(3)Hour函数很给力,组合条件要仔细 
select
    *
from
    cmb_usr_trx_rcd
where
    date(trx_time) 
    between '2024-09-01' and '2024-09-30' 
    and hour(trx_time) in (22,23,0,1,2,3,4,5)
    and usr_id = '5201314520' 
order by trx_time
2024-11-25 条件过滤(3)Hour函数很给力,组合条件要仔细 
select
    *
from
    cmb_usr_trx_rcd
where
    date(trx_time) 
    between '2024-09-01' and '2024-09-30' 
    or hour(trx_time) in (22,23,0,1,2,3,4,5)
    and usr_id = '5201314520' 
order by trx_time
2024-11-25 条件过滤(3)Hour函数很给力,组合条件要仔细 
select
    *
from
    cmb_usr_trx_rcd
where
    date(trx_time) 
    between '2024-09-01' and '2024-09-30' 
    and (
        (hour(trx_time) >= 22) 
        AND
        (hour(trx_time) between 0 and 5) 
    )
    and usr_id = '5201314520' 
order by trx_time
2024-11-25 条件过滤(2)半夜活动有猫腻,Hour函数给给力 
select * from cmb_usr_trx_rcd
where
    date(trx_time) 
    between '2024-09-01' and '2024-09-30' 
    and hour(trx_time) between 1 and 5 
    and usr_id = '5201314520' 
order by trx_time
2024-11-25 条件过滤(1)异地男友有异常,数分闺蜜来帮忙 
select * from cmb_usr_trx_rcd
where
    date(trx_time)  
    between '2024-09-01' and '2024-09-30'  
    and usr_id = '5201314520'  
order by
    trx_time