统计关键字个数

问题描述

某个表中有多行数据，其中第一列数据是一个ID编号，想知道该ID编号是不是该表的主键?

解决思路

wc -l file
awk -F"," '{print $1}' file | sort | uniq | wc -l

比较wc输出的行数是否一致

注意事项

1. 为什么需要sort呢？

• 答：uniq的一个特性，检查重复行的时候，只会检查相邻的行是否有重复数据，肯定存在重复数据不是在相邻位置的情况。

2. 实例

[root@localhost ~]# cat uniqtest    #测试文件
this is a test  
this is a test  
this is a test  
i am tank  
i love tank  
i love tank  
this is a test  
whom have a try  
WhoM have a try  
you  have a try  
i want to abroad  
those are good men  
we are good men  

[zhangy@BlackGhost mytest]$ uniq -c uniqtest    #uniq的一个特性，检查重复行的时候，只会检查相邻的行是否有重复数据，肯定存在重复数据不是在相邻位置的情况
 3 this is a test
 1 i am tank
 2 i love tank
 1 this is a test          #和第一行是重复的
 1 whom have a try
 1 WhoM have a try
 1 you? have a try
 1 i want to abroad
 1 those are good men
 1 we are good men

 [zhangy@BlackGhost mytest]$ sort uniqtest |uniq -c      #这样就可以解决上个例子中提到的问题
 1 WhoM have a try  
 1 i am tank  
 2 i love tank  
 1 i want to abroad  
 4 this is a test  
 1 those are good men  
 1 we are good men  
 1 whom have a try  
 1 you  have a try