zgm12的博客

一、外部表的创建、load、删除1.文件在本地而不是在hdfs的时候1.1 建表时指定location（1）建表并load数据create external table exTable28 (id int,str string) row format delimited fields terminated by ' ' location '/zgm/test/'; load data local inpath '/zgm2/exe28' into table exTable28;.

CREATE EXTERNAL TABLE userPhoto(uid string ,tag string ,tagweight double )ROW FORMAT SERDE'org.apache.hadoop.hive.hbase.HBaseSerDe'STORED BY'org.apache.hadoop.hive.hbase.HBaseStorageHandler'W...

一、求学生选的每门课都及格了的学生selecta.*from student2 ajoin(select b.sidfrom sc2 b group by b.sid having min(score)>60) con a.sid=c.sid;两个job taken: 84.528 seconds,select a.* from student2 a join s...

一、因为元数据的字段之间用：：分割，所以我们使用shell进行一下清洗,将：：都转换成逗号vi change1.sh#!/bin/bashsed "s/::/,/g" /zgm/movies.dat>/zgm/movies2.datsed "s/::/,/g" /zgm/ratings.dat>/zgm/ratings2.datsed "s/::/,/...

探究一下hql的执行顺序from … on … join … where … group by … having … select … distinct … order by … limit之前有个疑惑：explain select sid,min(score) as msfrom sc2 where sid>10group by sidhaving ms>60...

一、HQL写法uv:count(distinct)太影响性能，以下为改进：selecttmp.shop,count(1) as uvfrom(select user_id,shop from second_visit group by user_id,shop)tmpgroup by shop;pvselect shop,count(uid) from secon...

题目Student(Sid,Sname,Sage,Ssex)学生表Sid：学号 Sname：学生姓名Sbirth：学生生日Ssex：学生性别01 赵雷 1990-01-01 男02 钱电 1990-12-21 男03 孙风 1990-05-20 男04 李云 1990-08-06 男05 周梅 1991-12-01 女06 吴兰 1992-03-01 女...

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一、Group by1.1selectuname,floor(age/10) flagfrom programgroup by uname;会报错：FAILED: SemanticException [Error 10025]: Line 2:6 Expression not in GROUP BY key '10'原因：group by 后并没有age解决...

一、查询出的字段想要把列名改成中文，select s_id as '用户' from score;报错如下：NoViableAltException(313@[134:7: ( ( ( KW_AS )? identifier ) | ( KW_AS LPAREN identifier ( COMMA identifier )* RPAREN ) )?]) at or...

换座位小美是一所中学的信息科技老师，她有一张 seat 座位表，平时用来储存学生名字和与他们相对应的座位 id。其中纵列的 id 是连续递增的小美想改变相邻俩学生的座位。你能不能帮她写一个 SQL query 来输出小美想要的结果呢？示例：±--------±--------+| id | student |±--------±--------+| 1 | Abbot || 2...