之前有一位朋友咨询我，Impala中怎样实现将多列转为一行，事实上Impala中自带函数能够实现，不用自己定义函数。
以下我開始演示：
-bash-4.1$ impala-shell
Starting Impala Shell without Kerberos authentication Connected to cdha:21000 Server version: impalad version 1.4.2-cdh5 RELEASE (build eac952d4ff674663ec3834778c2b981b252aec78) Welcome to the Impala shell. Press TAB twice to see a list of available commands. Copyright (c) 2012 Cloudera, Inc. All rights reserved.(Shell build version: Impala Shell v1.4.2-cdh5 (eac952d) built on Tue Sep 16 19:15:40 PDT 2014)
[cdha:21000] > create table student(name string,subject string,score decimal(4,1)); -------------创建演示表：student(脱离学校四年了。还不忘自己是学生^_^) Query: create table student(name string,subject string,score decimal(4,1)) Returned 0 row(s) in 1.97s [cdha:21000] > insert into student values('xiaoming','math',89.5); ----------------插入演示数据 (小明和花花的学习成绩，他们感情比較好) Query: insert into student values('xiaoming','math',89.5) Inserted 1 rows in 2.56s [cdha:21000] > insert into student values('xiaoming','english',92); Query: insert into student values('xiaoming','english',92) Inserted 1 rows in 0.39s [cdha:21000] > insert into student values('xiaoming','chinese',98); Query: insert into student values('xiaoming','chinese',98) Inserted 1 rows in 0.42s [cdha:21000] > insert into student values('huahua','chinese',80); Query: insert into student values('huahua','chinese',80) Inserted 1 rows in 0.40s [cdha:21000] > insert into student values('huahua','math',89.5); Query: insert into student values('huahua','math',89.5) Inserted 1 rows in 0.29s [cdha:21000] > select * from student; ----------每次考完试，老师报分数时都非常紧张 Query: select * from student +----------+---------+-------+ | name | subject | score | +----------+---------+-------+ | xiaoming | english | 92.0 | | huahua | chinese | 80.0 | | xiaoming | chinese | 98.0 | | huahua | math | 89.5 | | xiaoming | math | 89.5 | +----------+---------+-------+ Returned 5 row(s) in 0.23s [cdha:21000] > select name,group_concat(subject,',') from student group by name; ------------小试牛刀，看到了吧，多列拼接到一起了 Query: select name,group_concat(subject,',') from student group by name +----------+----------------------------+ | name | group_concat(subject, ',') | +----------+----------------------------+ | xiaoming | english,chinese,math | | huahua | chinese,math | +----------+----------------------------+ Returned 2 row(s) in 0.38s------------以下演示有价值的演示样例，显示高手之招，呵呵
------------这样就能够在一行上面，看到小明和花花的各科成绩了
[cdha:21000] > select name,group_concat(concat_ws('=',subject,cast(score as string)),',') from student group by name; Query: select name,group_concat(concat_ws('=',subject,cast(score as string)),',') from student group by name +----------+-------------------------------------------------------------------+ | name | group_concat(concat_ws('=', subject, cast(score as string)), ',') | +----------+-------------------------------------------------------------------+ | xiaoming | english=92.0,chinese=98.0,math=89.5 | | huahua | chinese=80.0,math=89.5 | +----------+-------------------------------------------------------------------+ Returned 2 row(s) in 0.39s [cdha:21000] >Hive的行列转换请查看： http://blog.csdn.net/jiangshouzhuang/article/details/46810529