zoukankan      html  css  js  c++  java
  • SQL 每个分类各取2条数据

    create table tb (ptoid int,proclassid int,proname varchar(10))
    insert tb
    select 1,1,'衣服1'
    union all
    select 2,2,'衣服2'
    union all
    select 3,3,'衣服3'
    union all
    select 4,3,'衣服4'
    union all
    select 5,2,'衣服5'
    union all
    select 6,2,'衣服6'
    union all
    select 7,2,'衣服7'
    union all
    select 8,1,'衣服8'

    select * from tb

    ptoid       proclassid  proname   
    ----------- ----------- ----------
    1           1           衣服1
    2           2           衣服2
    3           3           衣服3
    4           3           衣服4
    5           2           衣服5
    6           2           衣服6
    7           2           衣服7
    8           1           衣服8

    (所影响的行数为 8 行)

    select * from tb a where
    (select count(*) from tb b where b.proclassid=a.proclassid and b.ptoid>a.ptoid) <2
    order by proclassid

    ptoid       proclassid  proname   
    ----------- ----------- ----------
    1           1           衣服1
    8           1           衣服8
    7           2           衣服7
    6           2           衣服6
    4           3           衣服4
    3           3           衣服3

    (所影响的行数为 6 行)

  • 相关阅读:
    【c语言趣味编程100例】爱因斯坦数学题
    【c语言趣味编程100例】求车速
    【c语言】sizeof和strlen函数区别
    Spiral Matrix I, II
    Trapping Rain Water
    Word Ladder**
    Minimum Size Subarray Sum
    Longest Substrings Without Repeating Characters
    Palindrome Linked List
    Container With Most Water
  • 原文地址:https://www.cnblogs.com/gdjlc/p/2086925.html
Copyright © 2011-2022 走看看