mysql & mine

• 常用的 MySQL 内置函数

DAY(date)     返回date的天数部分

HOUR(time)     返回time的小时值(0~23)

MINUTE(time)       返回time的分钟值(0~59)

SECOND(time)     返回time的秒值（0-59）

DATE(datetime)     返回datetime的日期值

TIME(datetime)     返回datetime的时间值

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• 按月计算指定年数的每个月的用户出现次数

SELECT
    t.myYear AS 年份,
    t.monthNo AS 月份,
    count(1) AS 数量统计
FROM
    (
        SELECT
            MONTH (pi_gym_enter.create_date) AS monthNo,  //这里指定日期字段为 create_date
            YEAR (pi_gym_enter.create_date) AS myYear,
            pi_gym_enter.id AS id
        FROM
            pi_gym_enter WHERE getr_member_id = 5 // 这里指定用户
    ) AS t
WHERE
    t.myYear = '2018'  // 这里指定年份
GROUP BY
    t.monthNo;

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• 统计前一天的日志sql语句：

select * from bean where date(usedate) = date_sub(curdate(),interval 1 day);
// 括号中为当天时间的前一天，如果统计前几天就将括号中的’1’改成相应的天数。

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• 计算该用户指定时间内，每天出现的次数和

SELECT
    getr_member_id,
    DATE(create_date),
    sum(getr_time),
    create_date
FROM
    pi_gym_enter
WHERE
    getr_member_id = 5
AND (
    `create_date` BETWEEN '2018-03-01 00:00:00'
    AND '2018-04-01 00:00:00'
)
GROUP BY
    DATE(create_date)

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• 多表联查的套用模板

SELECT T1.C1,T2.CX,T3.CY
FROM TAB1 T1
       INNER JOIN TAB2 T2 ON (T1.C1=T2.C2)
       INNER JOIN TAB3 T3 ON (T1.C1=T2.C3)
       LEFT OUTER JOIN TAB4 ON(T2.C2=T3.C3);
WHERE T1.X >T3.Y;

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• mysql 行数据转列数据套用模板

SELECT DISTINCT  a.sname,  
(SELECT score FROM stdscore b WHERE a.sname=b.sname AND b.CNAME='JAVA' ) AS 'JAVA',  
(SELECT score FROM stdscore b WHERE a.sname=b.sname AND b.CNAME='mysql' ) AS 'mysql' 
FROM stdscore a