Hive 学习（五） Hive之HSQL基础

客官°小女子只卖身不卖艺 2021-11-02 00:14 308阅读 0赞

**一，前言**

**二，连接查询**

2.1 内连接（join | inner join）

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）

2.5 左半连接（left semi join）

**三，分组聚合**

3.1 分组聚合须知

3.2 分组聚合练习1

3.3 分组聚合练习2

**四，条件判断**

**　　**4.1 case...when...

4.2 if判断

# 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   |
    +----------------+---------------------------------+-----------------------+--------------+

## 四，条件判断 ##

数据下载：[点击下载][Link 1]

### 　　4.1 case...when... ###

语法结构：

case  // 开始提示符
        when 条件1 then 符合条件1的结果
        when 条件2 then 符合条件2的结果
        else 上述都不符合的结果
    end   //结束提示符

表创建和数据导入：

create table t_user(id int,name string,info struct<age:int,sex:string,addr:string>)
    row format delimited fields terminated by ','
    collection items terminated by ':';
    
    -- 导入数据
    load data local inpath '/root/hivetest/user.dat' into table t_user;

数据查询：

select * from t_user;
    +------------+--------------+----------------------------------------+--+
    | t_user.id  | t_user.name  |              t_user.info               |
    +------------+--------------+----------------------------------------+--+
    | 1          | zhangsan     | {"age":18,"sex":"male","addr":"深圳"}    |
    | 2          | lisi         | {"age":28,"sex":"female","addr":"北京"}  |
    | 3          | wangwu       | {"age":38,"sex":"male","addr":"广州"}    |
    | 4          | 赵六           | {"age":26,"sex":"female","addr":"上海"}  |
    | 5          | 钱琪           | {"age":35,"sex":"male","addr":"杭州"}    |
    | 6          | 王八           | {"age":48,"sex":"female","addr":"南京"}  |
    +------------+--------------+----------------------------------------+--+

需求：查询出用户的id、name、年龄（如果年龄在30岁以下，显示年轻人，30-40之间，显示中年人，40以上老年人）

需求实现：

select id,name,
    case
    　　when info.age<30 then '青年'
    　　when info.age>=30 and info.age<40 then '中年'
    　　else '老年'
    end
    from t_user;

### 　　4.2 if判断 ###

语法结构：

if(条件，条件成立结果，条件不成立结果)

表创建和数据导入：

-- 建表映射：
    create table t_movie(movie_name string,actors array<string>,first_show date)
    row format delimited fields terminated by ','
    collection items terminated by ':';
    
    -- 导入数据
    load data local inpath '/root/hivetest/actor.dat' into table t_movie;

数据查询：

需求：查询电影信息，并且如果主演中有吴刚的，显示好电影，否则烂片

需求实现：

select movie_name,actors,first_show,
    if(array_contains(actors,'吴刚'),'好片儿','烂片儿')
    from t_movie;

转载于:https://www.cnblogs.com/tashanzhishi/p/10901234.html

[access.log]: https://files.cnblogs.com/files/tashanzhishi/hive%E7%BB%83%E4%B9%A0%E7%94%A8%E6%95%B0%E6%8D%AE.rar
[Link 1]: https://files.cnblogs.com/files/tashanzhishi/hive%E6%9D%A1%E4%BB%B6%E7%BB%83%E4%B9%A0%E6%95%B0%E6%8D%AE.rar