zoukankan      html  css  js  c++  java
  • SQL语句积累1:自身查询、区间查询、同号排查

    数据库表:t_persons  

    select * from t_persons

    ID      name          date                                         money
    1        李天       2012-01-01 00:00:00.000               100
    2        李忠       2012-02-01 00:00:00.000               200
    3        李天       2012-01-01 00:00:00.000               100
    4        李忠       2012-02-02 00:00:00.000               500
    5        李敏       2011-01-01 00:00:00.000               600
    6        李吧       2011-02-03 00:00:00.000              1000

    1.

    /*查询相同名字的最大时间的记录*/
    select * from t_persons a where a.date=(select max(date) from t_persons b where b.name=a.name)

    2.

    /*区间数据: 前第4-5条记录*/
    select top 2 * from( select top 5 * from t_persons order by ID asc ) a order by ID desc
    select top 2 * from t_persons where ID not in (select top 3 ID from t_persons)

    扩展:

    以查询前20到30条为例,主键名为id 

    方法一: 先正查,再反查 
    select top 10 * from (select top 30 * from tablename order by id asc) A order by id desc 

    方法二: 使用left join 
    select top 10 A.* from tablename A 
    left outer join (select top 20 * from tablename order by id asc) B 
    on A.id = B.id 
    where B.id is null 
    order by A.id asc 

    方法三: 使用not exists 
    select top 10 * from tablename A 
    where id not exists 
    (select top 20 * from tablename B on A.id = B.id) 

    方法四: 使用not in 
    select top 10 * from tablename 
    where id not in 
    (select top 20 id from tablename order by id asc) 
    order by id asc 

    方法五: 使用rank() 
    select id from 
    (select rank() over(order by id asc) rk, id from tablename) T 
    where rk between 20 and 30 

    中第五种方法看上去好像没有问题,查了下文档,当over()用于rank/row_number时,整型列不能描述一个列,所以会产生非预期的效果. 待考虑下,有什么办法可以修改为想要的结果.

    3.删除重复的数据,只留一条

    select * from t_persons where ID=
    (select max(ID) from t_persons where
    name =(select name from t_persons group by name,date,money having count(*)>1)
    and date=(select date from t_persons group by name,date,money having count(*)>1)
    and money=(select money from t_persons group by name,date,money having count(*)>1)
    )

  • 相关阅读:
    自定义实现wcf的用户名密码验证
    EF6:编写你自己的code first 数据迁移操作(睡前来一篇,翻译的)
    .net 连接Redis
    idea external libraries 只有jdk问题
    MAC vim安装gruvbox主题
    Mac gitk安装与优化
    spring security 4 filter 顺序及作用
    mysql 采样查询 / 间隔查询 / 跳跃查询的两种实现思路
    nginx warn an upstream response is buffered to a temporary file /var/cache/nginx/proxy_temp/ while reading upstream
    nginx日志 logrotate配置
  • 原文地址:https://www.cnblogs.com/lvfeilong/p/AFKFAJ234.html
Copyright © 2011-2022 走看看