Hive聚合函数和表生成函数

一 聚合函数

1、count

2、sum

3、min

4、max

5、avg

二 实例

hive> select count(*),sum(sal),max(sal),min(sal),avg(sal) from emp;Total jobs = 1Launching Job 1 out of 1Number of reduce tasks determined at compile time: 1In order to change the average load for a reducer (in bytes):  set hive.exec.reducers.bytes.per.reducer=<number>In order to limit the maximum number of reducers:  set hive.exec.reducers.max=<number>In order to set a constant number of reducers:  set mapred.reduce.tasks=<number>Starting Job = job_201709011948_0004, Tracking URL = http://localhost:50030/jobdetails.jsp?jobid=job_201709011948_0004Kill Command = /opt/hadoop-1.2.1/libexec/../bin/hadoop job  -kill job_201709011948_0004Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 12017-09-01 20:43:25,420 Stage-1 map = 0%,  reduce = 0%2017-09-01 20:43:42,444 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 2.72 sec2017-09-01 20:44:10,270 Stage-1 map = 100%,  reduce = 67%, Cumulative CPU 3.44 sec2017-09-01 20:44:12,320 Stage-1 map = 100%,  reduce = 100%, Cumulative CPU 9.34 secMapReduce Total cumulative CPU time: 9 seconds 340 msecEnded Job = job_201709011948_0004MapReduce Jobs Launched: Job 0: Map: 1  Reduce: 1   Cumulative CPU: 9.34 sec   HDFS Read: 635 HDFS Write: 35 SUCCESSTotal MapReduce CPU Time Spent: 9 seconds 340 msecOK16104236.012111.04800.06514.75Time taken: 86.66 seconds, Fetched: 1 row(s)

三 表生成函数

explode

四 实例

hive> select explode(map(1,'Tom',2,'Mary',3,'Mike'));Total jobs = 1Launching Job 1 out of 1Number of reduce tasks is set to 0 since there's no reduce operatorStarting Job = job_201709011948_0005, Tracking URL = http://localhost:50030/jobdetails.jsp?jobid=job_201709011948_0005Kill Command = /opt/hadoop-1.2.1/libexec/../bin/hadoop job  -kill job_201709011948_0005Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 02017-09-01 20:46:33,297 Stage-1 map = 0%,  reduce = 0%2017-09-01 20:46:47,588 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 3.27 sec2017-09-01 20:46:55,793 Stage-1 map = 100%,  reduce = 100%, Cumulative CPU 3.27 secMapReduce Total cumulative CPU time: 3 seconds 270 msecEnded Job = job_201709011948_0005MapReduce Jobs Launched: Job 0: Map: 1   Cumulative CPU: 3.27 sec   HDFS Read: 270 HDFS Write: 20 SUCCESSTotal MapReduce CPU Time Spent: 3 seconds 270 msecOK1Tom2Mary3MikeTime taken: 42.023 seconds, Fetched: 3 row(s)