如何从复合主键表中选择*答案

【问题标题】：How select * from composite primary key table如何从复合主键表中选择*
【发布时间】：2018-03-18 04:49:42
【问题描述】：

我学到了How select distinct from composite primary key table：

; with temp as (
 select row_number() over (partition by First_PK order by Second_PK desc)
   as row_num, First_PK, Second_PK, data
 from test)
 select * from temp
 where row_num = 1

但我现在面临另一个问题，而不是where row_num = 1 我想要where row_num = MAX（我的意思是最大值）

How select distinct from composite primary key table

【问题讨论】：

你能指定你的样本数据和预期的输出吗..？
我想SELECT * 取决于Second_PK 的最大值
因为您是按 descending 顺序订购 Second_PK，所以选择 where row_num = 1 应该已经为您提供 Second_PK 的最大值（基于您的分区First_PK)

标签： sql sql-server

【解决方案1】：

由于一个排序顺序的最后一行将是相反排序顺序的第一行，您只需将order by子句更改为在窗口函数row_number中使用升序即可：

; with temp as (
 select row_number() over (partition by First_PK order by Second_PK)
   as row_num, First_PK, Second_PK, data
 from test)
 select * from temp
 where row_num = 1

【讨论】：

【解决方案2】：

解决方案是：

; with temp as (
 select row_number() over (partition by First_PK order by Second_PK)
   as row_num, First_PK, Second_PK, data
 from test)
 select * from temp
 WHERE row_num=(SELECT max(row_num) FROM temp);

【讨论】：