2.2 左外连接（left join | left outer join）
2.3 右外连接（right join | right outer join）
2.4 全外连接（full join | full outer join）
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正文
一，前言
和其他SQL一样，HSQL与其他的SQL差别不大，在这就进行一些简单的介绍。
二，连接查询
数据准备和表创建如下：
create table t_a(name string,numb int) row format delimited fields terminated by ','; create table t_b(name string,nick string) row format delimited fields terminated by ','; load data local inpath '/root/hivetest/a.txt' into table t_a; load data local inpath '/root/hivetest/b.txt' into table t_b; 0: jdbc:hive2://localhost:10000> select * from t_a; +-----------+-----------+--+ | t_a.name | t_a.numb | +-----------+-----------+--+ | a | 4 | | b | 5 | | c | 6 | | d | 8 | +-----------+-----------+--+ 4 rows selected (0.197 seconds) 0: jdbc:hive2://localhost:10000> select * from t_b; +-----------+-----------+--+ | t_b.name | t_b.nick | +-----------+-----------+--+ | a | laowang | | b | qiangzi | | d | paoge | | g | haizi | +-----------+-----------+--+ 4 rows selected (0.135 seconds)
2.1 内连接（join | inner join）
-- 各类join --1/ 内连接 -- 笛卡尔积 select a.*,b.* from t_a a inner join t_b b; // inner join == join +-----------+-----------+-----------+-----------+--+ | t_a.name | t_a.numb | t_b.name | t_b.nick | +-----------+-----------+-----------+-----------+--+ | a | 4 | a | laowang | | b | 5 | a | laowang | | c | 6 | a | laowang | | d | 8 | a | laowang | | a | 4 | b | qiangzi | | b | 5 | b | qiangzi | | c | 6 | b | qiangzi | | d | 8 | b | qiangzi | | a | 4 | d | paoge | | b | 5 | d | paoge | | c | 6 | d | paoge | | d | 8 | d | paoge | | a | 4 | g | haizi | | b | 5 | g | haizi | | c | 6 | g | haizi | | d | 8 | g | haizi | +-----------+-----------+-----------+-----------+--+ 16 rows selected (14.104 seconds) -- 指定join条件 select a.*,b.* from t_a a join t_b b on a.name=b.name; +---------+---------+---------+----------+--+ | a.name | a.numb | b.name | b.nick | +---------+---------+---------+----------+--+ | a | 4 | a | laowang | | b | 5 | b | qiangzi | | d | 8 | d | paoge | +---------+---------+---------+----------+--+ 3 rows selected (13.429 seconds)
2.2 左外连接（left join | left outer join）
-- 2/ 左外连接（左连接） select a.*,b.* from t_a a left outer join t_b b on a.name=b.name; +---------+---------+---------+----------+--+ | a.name | a.numb | b.name | b.nick | +---------+---------+---------+----------+--+ | a | 4 | a | laowang | | b | 5 | b | qiangzi | | c | 6 | NULL | NULL | | d | 8 | d | paoge | +---------+---------+---------+----------+--+ 4 rows selected (9.25 seconds)
2.3 右外连接（right join | right outer join）
-- 3/ 右外连接（右连接） select a.*,b.* from t_a a right outer join t_b b on a.name=b.name; +---------+---------+---------+----------+--+ | a.name | a.numb | b.name | b.nick | +---------+---------+---------+----------+--+ | a | 4 | a | laowang | | b | 5 | b | qiangzi | | d | 8 | d | paoge | | NULL | NULL | g | haizi | +---------+---------+---------+----------+--+ 4 rows selected (8.914 seconds)
2.4 全外连接（full join | full outer join）
-- 4/ 全外连接 select a.*,b.* from t_a a full outer join t_b b on a.name=b.name; +---------+---------+---------+----------+--+ | a.name | a.numb | b.name | b.nick | +---------+---------+---------+----------+--+ | a | 4 | a | laowang | | b | 5 | b | qiangzi | | c | 6 | NULL | NULL | | d | 8 | d | paoge | | NULL | NULL | g | haizi | +---------+---------+---------+----------+--+ 5 rows selected (1.74 seconds)
2.5 左半连接（left semi join）
注意：left semi是HSQL特有，且没有右半连接
-- 5/ 左半连接 :注意没有右半连接 select a.* from t_a a left semi join t_b b on a.name=b.name; +---------+---------+--+ | a.name | a.numb | +---------+---------+--+ | a | 4 | | b | 5 | | d | 8 | +---------+---------+--+ 3 rows selected (12.236 seconds)
三，分组聚合
数据下载：access.log
表创建和数据插入：
create table t_access(ip string,url string,access_time string) partitioned by (dt string) row format delimited fields terminated by ','; -- 导入数据 load data local inpath '/root/hivetest/access.log.0804' into table t_access partition(dt='2017-08-04'); load data local inpath '/root/hivetest/access.log.0805' into table t_access partition(dt='2017-08-05'); load data local inpath '/root/hivetest/access.log.0806' into table t_access partition(dt='2017-08-06'); -- 查看表的分区 show partitions t_access;
3.1 分组聚合须知
一旦有group by子句，那么，在select子句中就不能有 （分组字段，聚合函数） 以外的字段
3.2 分组聚合练习1
-- 针对每一行进行运算 select ip,upper(url),access_time -- 该表达式是对数据中的每一行进行逐行运算 from t_access; -- 求每条URL的访问总次数 select url,count(1) as cnts -- 该表达式是对分好组的数据进行逐组运算 from t_access group by url; +---------------------------------+------+--+ | url | _c1 | +---------------------------------+------+--+ | http://www.edu360.cn/excersize | 3 | | http://www.edu360.cn/job | 7 | | http://www.edu360.cn/pay | 1 | | http://www.edu360.cn/register | 2 | | http://www.edu360.cn/stu | 4 | | http://www.edu360.cn/teach | 2 | +---------------------------------+------+--+ 6 rows selected (1.683 seconds) -- 求每个URL的访问者中ip地址最大的 select url,max(ip) from t_pv_log group by url; +---------------------------------+----------------+--+ | url | _c1 | +---------------------------------+----------------+--+ | http://www.edu360.cn/excersize | 192.168.33.46 | | http://www.edu360.cn/job | 192.168.33.55 | | http://www.edu360.cn/pay | 192.168.34.44 | | http://www.edu360.cn/register | 192.168.133.3 | | http://www.edu360.cn/stu | 192.168.33.44 | | http://www.edu360.cn/teach | 192.168.44.3 | +---------------------------------+----------------+--+ 6 rows selected (1.595 seconds) -- 求每个用户访问同一个页面的所有记录中，时间最晚的一条 select ip,url,max(access_time) from t_pv_log group by ip,url; +----------------+---------------------------------+----------------------+--+ | it | url | _c2 | +----------------+---------------------------------+----------------------+--+ | 192.168.111.3 | http://www.edu360.cn/register | 2017-08-06 15:35:20 | | 192.168.133.3 | http://www.edu360.cn/register | 2017-08-06 15:30:20 | | 192.168.33.25 | http://www.edu360.cn/job | 2017-08-06 15:40:20 | | 192.168.33.3 | http://www.edu360.cn/stu | 2017-08-05 15:30:20 | | 192.168.33.3 | http://www.edu360.cn/teach | 2017-08-04 15:35:20 | | 192.168.33.36 | http://www.edu360.cn/excersize | 2017-08-06 16:30:20 | | 192.168.33.4 | http://www.edu360.cn/job | 2017-08-04 16:30:20 | | 192.168.33.4 | http://www.edu360.cn/stu | 2017-08-04 15:30:20 | | 192.168.33.44 | http://www.edu360.cn/stu | 2017-08-05 15:30:20 | | 192.168.33.46 | http://www.edu360.cn/excersize | 2017-08-06 16:30:20 | | 192.168.33.46 | http://www.edu360.cn/job | 2017-08-05 16:30:20 | | 192.168.33.5 | http://www.edu360.cn/job | 2017-08-04 15:40:20 | | 192.168.33.55 | http://www.edu360.cn/job | 2017-08-06 15:40:20 | | 192.168.34.44 | http://www.edu360.cn/pay | 2017-08-06 15:30:20 | | 192.168.44.3 | http://www.edu360.cn/teach | 2017-08-05 15:35:20 | +----------------+---------------------------------+----------------------+--+ 15 rows selected (1.597 seconds)
3.3 分组聚合练习二
-- 求8月4号以后，每天http://www.edu360.cn/job的总访问次数，及访问者中ip地址中最大的 select dt,'http://www.edu360.cn/job',count(1),max(it) from t_access where url='http://www.edu360.cn/job' group by dt having dt>'2017-08-04'; select dt,max(url),count(1),max(ip) from t_access where url='http://www.edu360.cn/job' group by dt having dt>'2017-08-04'; select dt,url,count(1),max(ip) from t_access where url='http://www.edu360.cn/job' group by dt,url having dt>'2017-08-04'; select dt,url,count(1),max(ip) from t_access where url='http://www.edu360.cn/job' and dt>'2017-08-04' group by dt,url; +-------------+---------------------------+------+----------------+--+ | dt | _c1 | _c2 | _c3 | +-------------+---------------------------+------+----------------+--+ | 2017-08-05 | http://www.edu360.cn/job | 2 | 192.168.33.55 | | 2017-08-06 | http://www.edu360.cn/job | 3 | 192.168.33.55 | +-------------+---------------------------+------+----------------+--+ 2 rows selected (1.609 seconds) -- 求8月4号以后，每天每个页面的总访问次数，及访问者中ip地址中最大的，且，只查询出总访问次数>2 的记录 -- 方式1： select dt,url,count(1) as cnts,max(ip) from t_access where dt>'2017-08-04' group by dt,url having cnts>2; -- 方式2：用子查询 select dt,url,cnts,max_ip from (select dt,url,count(1) as cnts,max(ip) as max_ip from t_access where dt>'2017-08-04' group by dt,url) tmp where cnts>2; +----------------+---------------------------------+-----------------------+--------------+--+ | t_access.ip | t_access.url | t_access.access_time | t_access.dt | +----------------+---------------------------------+-----------------------+--------------+--+ | 192.168.33.46 | http://www.edu360.cn/job | 2017-08-05 16:30:20 | 2017-08-05 | | 192.168.33.55 | http://www.edu360.cn/job | 2017-08-05 15:40:20 | 2017-08-05 | | 192.168.33.55 | http://www.edu360.cn/job | 2017-08-06 15:40:20 | 2017-08-06 | | 192.168.33.25 | http://www.edu360.cn/job | 2017-08-06 15:40:20 | 2017-08-06 | | 192.168.33.55 | http://www.edu360.cn/job | 2017-08-06 15:40:20 | 2017-08-06 | +----------------+---------------------------------+-----------------------+--------------+