大数据技术之Hive查询分区表和分桶表
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1 查询
查询语句语法:
SELECT [ALL | DISTINCT] select_expr, select_expr, ...
FROM table_reference
[WHERE where_condition]
[GROUP BY col_list]
[ORDER BY col_list]
[CLUSTER BY col_list]
| [DISTRIBUTE BY col_list] [SORT BY col_list]
[LIMIT number]
1.1 基本查询(Select…From)
1.1.1 全表和特定列查询
1. 数据准备
(1)原始数据
dept:
10 ACCOUNTING 1700
20 RESEARCH 1800
30 SALES 1900
40 OPERATIONS 1700
emp:
369 SMITH CLERK 7902 1980-12-17 800.00 20
7499 ALLEN SALESMAN 7698 1981-2-20 1600.00 300.00 30
7521 WARD SALESMAN 7698 1981-2-22 1250.00 500.00 30
7566 JONES MANAGER 7839 1981-4-2 2975.00 20
7654 MARTIN SALESMAN 7698 1981-9-28 1250.00 1400.00 30
7698 BLAKE MANAGER 7839 1981-5-1 2850.00 30
7782 CLARK MANAGER 7839 1981-6-9 2450.00 10
7788 SCOTT ANALYST 7566 1987-4-19 3000.00 20
7839 KING PRESIDENT 1981-11-17 5000.00 10
7844 TURNER SALESMAN 7698 1981-9-8 1500.00 0.00 30
7876 ADAMS CLERK 7788 1987-5-23 1100.00 20
7900 JAMES CLERK 7698 1981-12-3 950.00 30
7902 FORD ANALYST 7566 1981-12-3 3000.00 20
7934 MILLER CLERK 7782 1982-1-23 1300.00 10
7534 MILLER CLERK 7782 1982-10-23 1300.00 50
(2)创建部门表
create table if not exists dept(
deptno int,
dname string,
loc int
)
row format delimited fields terminated by '\\t';
(3)创建员工表
create table if not exists emp(
empno int,
ename string,
job string,
mgr int,
hiredate string,
sal double,
comm double,
deptno int)
row format delimited fields terminated by '\\t';
(4)导入数据
hive (default)> load data local inpath '/opt/module/hive-3.1.2/data/dept.txt' into table dept;
hive (default)> load data local inpath '/opt/module/hive-3.1.2/data/emp.txt' into table emp;
2. 全表查询
hive (default)> select * from emp;
OK
emp.empno emp.ename emp.job emp.mgr emp.hiredate emp.sal emp.comm emp.deptno
7369 SMITH CLERK 7902 1980-12-17 800.0 NULL 20
7499 ALLEN SALESMAN 7698 1981-2-20 1600.0 300.0 30
7521 WARD SALESMAN 7698 1981-2-22 1250.0 500.0 30
7566 JONES MANAGER 7839 1981-4-2 2975.0 NULL 20
7654 MARTIN SALESMAN 7698 1981-9-28 1250.0 1400.0 30
7698 BLAKE MANAGER 7839 1981-5-1 2850.0 NULL 30
7782 CLARK MANAGER 7839 1981-6-9 2450.0 NULL 10
7788 SCOTT ANALYST 7566 1987-4-19 3000.0 NULL 20
7839 KING PRESIDENT NULL 1981-11-17 5000.0 NULL 10
7844 TURNER SALESMAN 7698 1981-9-8 1500.0 0.0 30
7876 ADAMS CLERK 7788 1987-5-23 1100.0 NULL 20
7900 JAMES CLERK 7698 1981-12-3 950.0 NULL 30
7902 FORD ANALYST 7566 1981-12-3 3000.0 NULL 20
7934 MILLER CLERK 7782 1982-1-23 1300.0 NULL 10
7534 MILLER CLERK 7782 1982-10-23 1300.0 NULL 50
Time taken: 0.271 seconds, Fetched: 15 row(s)
hive (default)> select empno, ename, job, mgr, hiredate, sal, comm, deptno from emp;
OK
empno ename job mgr hiredate sal comm deptno
7369 SMITH CLERK 7902 1980-12-17 800.0 NULL 20
7499 ALLEN SALESMAN 7698 1981-2-20 1600.0 300.0 30
7521 WARD SALESMAN 7698 1981-2-22 1250.0 500.0 30
7566 JONES MANAGER 7839 1981-4-2 2975.0 NULL 20
7654 MARTIN SALESMAN 7698 1981-9-28 1250.0 1400.0 30
7698 BLAKE MANAGER 7839 1981-5-1 2850.0 NULL 30
7782 CLARK MANAGER 7839 1981-6-9 2450.0 NULL 10
7788 SCOTT ANALYST 7566 1987-4-19 3000.0 NULL 20
7839 KING PRESIDENT NULL 1981-11-17 5000.0 NULL 10
7844 TURNER SALESMAN 7698 1981-9-8 1500.0 0.0 30
7876 ADAMS CLERK 7788 1987-5-23 1100.0 NULL 20
7900 JAMES CLERK 7698 1981-12-3 950.0 NULL 30
7902 FORD ANALYST 7566 1981-12-3 3000.0 NULL 20
7934 MILLER CLERK 7782 1982-1-23 1300.0 NULL 10
7534 MILLER CLERK 7782 1982-10-23 1300.0 NULL 50
Time taken: 0.323 seconds, Fetched: 15 row(s)
3. 选择特定列查询
hive (default)> select empno, ename from emp;
OK
empno ename
7369 SMITH
7499 ALLEN
7521 WARD
7566 JONES
7654 MARTIN
7698 BLAKE
7782 CLARK
7788 SCOTT
7839 KING
7844 TURNER
7876 ADAMS
7900 JAMES
7902 FORD
7934 MILLER
7534 MILLER
Time taken: 0.279 seconds, Fetched: 15 row(s)
注意:
(1)SQL 语言 大小写不敏感。
(2)SQL 可以写在一行或者多行
(3)关键字不能被缩写也不能分行
(4)各子句一般要分行写。
(5)使用缩进提高语句的可读性。
1.1.2 列别名
重命名一个列便于计算。命名方法为紧跟列名,也可以在列名和别名之间加入关键字AS
。
实例:查询名称和部门
hive (default)> select ename as name, deptno dn from emp;
OK
name dn
SMITH 20
ALLEN 30
WARD 30
JONES 20
MARTIN 30
BLAKE 30
CLARK 10
SCOTT 20
KING 10
TURNER 30
ADAMS 20
JAMES 30
FORD 20
MILLER 10
MILLER 50
Time taken: 0.289 seconds, Fetched: 15 row(s)
1.1.3 算术运算符
案例实操:查询出所有员工的薪水后加 1 显示。
hive (default)> select sal+1 from emp;
OK
_c0
801.0
1601.0
1251.0
2976.0
1251.0
2851.0
2451.0
3001.0
5001.0
1501.0
1101.0
951.0
3001.0
1301.0
1301.0
Time taken: 0.79 seconds, Fetched: 15 row(s)
1.1.4 常用函数
(1)求总行数(count)
hive (default)> select count(*) cnt from emp;
OK
cnt
15
Time taken: 20.637 seconds, Fetched: 1 row(s)
(2)求工资的最大值(max)
hive (default)> select max(sal) max_sal from emp;
OK
max_sal
5000.0
Time taken: 19.305 seconds, Fetched: 1 row(s)
(3)求工资的最小值(min)
hive (default)> select min(sal) min_sal from emp;
OK
min_sal
800.0
Time taken: 31.402 seconds, Fetched: 1 row(s)
(4)求工资的总和(sum)
hive (default)> select sum(sal) sum_sal from emp;
OK
sum_sal
30325.0
Time taken: 8.185 seconds, Fetched: 1 row(s)
(5)求工资的平均值(avg)
hive (default)> select avg(sal) avg_sal from emp;
OK
avg_sal
2021.6666666666667
Time taken: 8.706 seconds, Fetched: 1 row(s)
1.1.5 Limit 语句
典型的查询会返回多行数据。LIMIT 子句用于限制返回的行数。
hive (default)> select * from emp limit 3;
OK
emp.empno emp.ename emp.job emp.mgr emp.hiredate emp.sal emp.comm emp.deptno
7369 SMITH CLERK 7902 1980-12-17 800.0 NULL 20
7499 ALLEN SALESMAN 7698 1981-2-20 1600.0 300.0 30
7521 WARD SALESMAN 7698 1981-2-22 1250.0 500.0 30
Time taken: 0.318 seconds, Fetched: 3 row(s)
hive (default)> select sal from emp limit 5;
OK
sal
800.0
1600.0
1250.0
2975.0
1250.0
Time taken: 0.298 seconds, Fetched: 5 row(s)
1.1.6 Where 语句
使用 WHERE 子句,将不满足条件的行过滤掉。
WHERE 子句紧随 FROM 子句。WHERE 子句中不能使用字段别名。
例:查询出薪水大于2000 的所有员工:
hive (default)> select * from emp where sal > 2000;
OK
emp.empno emp.ename emp.job emp.mgr emp.hiredate emp.sal emp.comm emp.deptno
7566 JONES MANAGER 7839 1981-4-2 2975.0 NULL 20
7698 BLAKE MANAGER 7839 1981-5-1 2850.0 NULL 30
7782 CLARK MANAGER 7839 1981-6-9 2450.0 NULL 10
7788 SCOTT ANALYST 7566 1987-4-19 3000.0 NULL 20
7839 KING PRESIDENT NULL 1981-11-17 5000.0 NULL 10
7902 FORD ANALYST 7566 1981-12-3 3000.0 NULL 20
Time taken: 0.324 seconds, Fetched: 6 row(s)
1.1.7 比较运算符(Between / In / Is Null)
下面表中描述了谓词操作符,这些操作符同样可以用于 JOIN…ON和 HAVING语句中。
例:(1)查询出薪水等于 5000 的所有员工
hive (default)> select * from emp where sal=5000;
OK
emp.empno emp.ename emp.job emp.mgr emp.hiredate emp.sal emp.comm emp.deptno
7839 KING PRESIDENT NULL 1981-11-17 5000.0 NULL 10
Time taken: 0.312 seconds, Fetched: 1 row(s)
(2)查询工资在 800到 950 的员工信息
hive (default)> select * from emp where sal between 800 and 950;
OK
emp.empno emp.ename emp.job emp.mgr emp.hiredate emp.sal emp.comm emp.deptno
7369 SMITH CLERK 7902 1980-12-17 800.0 NULL 20
7900 JAMES CLERK 7698 1981-12-3 950.0 NULL 30
Time taken: 0.267 seconds, Fetched: 2 row(s)
(3)查询 comm 为空的所有员工信息
hive (default)> select * from emp where comm is null;
OK
emp.empno emp.ename emp.job emp.mgr emp.hiredate emp.sal emp.comm emp.deptno
7369 SMITH CLERK 7902 1980-12-17 800.0 NULL 20
7566 JONES MANAGER 7839 1981-4-2 2975.0 NULL 20
7698 BLAKE MANAGER 7839 1981-5-1 2850.0 NULL 30
7782 CLARK MANAGER 7839 1981-6-9 2450.0 NULL 10
7788 SCOTT ANALYST 7566 1987-4-19 3000.0 NULL 20
7839 KING PRESIDENT NULL 1981-11-17 5000.0 NULL 10
7876 ADAMS CLERK 7788 1987-5-23 1100.0 NULL 20
7900 JAMES CLERK 7698 1981-12-3 950.0 NULL 30
7902 FORD ANALYST 7566 1981-12-3 3000.0 NULL 20
7934 MILLER CLERK 7782 1982-1-23 1300.0 NULL 10
7534 MILLER CLERK 7782 1982-10-23 1300.0 NULL 50
Time taken: 0.283 seconds, Fetched: 11 row(s)
(4)查询工资是 1500 或 5000 的员工信息
hive (default)> select * from emp where sal in (1500, 5000);
OK
emp.empno emp.ename emp.job emp.mgr emp.hiredate emp.sal emp.comm emp.deptno
7839 KING PRESIDENT NULL 1981-11-17 5000.0 NULL 10
7844 TURNER SALESMAN 7698 1981-9-8 1500.0 0.0 30
Time taken: 0.299 seconds, Fetched: 2 row(s)
1.1.8 Like和RLike
(1)使用 LIKE 运算选择类似的值。
(2)选择条件可以包含字符或数字。
% 代表零个或多个字符任意个字符 。
_ 代表一个字符。
(3)RLIKE 子句 是 Hive 中这个功能的一个扩展,其可以通过 Java 的正则表达式这个更强大的语言来指定匹配条件。
案例实操
查找名字以 A 开头的员工信息
hive (default)> select * from emp where ename like 'A%';
OK
emp.empno emp.ename emp.job emp.mgr emp.hiredate emp.sal emp.comm emp.deptno
7499 ALLEN SALESMAN 7698 1981-2-20 1600.0 300.0 30
7876 ADAMS CLERK 7788 1987-5-23 1100.0 NULL 20
查找名字中第二个字母为 A 的员工信息
hive (default)> select * from emp where ename like '_A%';
OK
emp.empno emp.ename emp.job emp.mgr emp.hiredate emp.sal emp.comm emp.deptno
7521 WARD SALESMAN 7698 1981-2-22 1250.0 500.0 30
7654 MARTIN SALESMAN 7698 1981-9-28 1250.0 1400.0 30
7900 JAMES CLERK 7698 1981-12-3 950.0 NULL 30
Time taken: 0.301 seconds, Fetched: 3 row(s)
查找名字中带有 A 的员工信息
hive (default)> select * from emp where ename rlike '[A]';
OK
emp.empno emp.ename emp.job emp.mgr emp.hiredate emp.sal emp.comm emp.deptno
7499 ALLEN SALESMAN 7698 1981-2-20 1600.0 300.0 30
7521 WARD SALESMAN 7698 1981-2-22 1250.0 500.0 30
7654 MARTIN SALESMAN 7698 1981-9-28 1250.0 1400.0 30
7698 BLAKE MANAGER 7839 1981-5-1 2850.0 NULL 30
7782 CLARK MANAGER 7839 1981-6-9 2450.0 NULL 10
7876 ADAMS CLERK 7788 1987-<以上是关于大数据技术之Hive查询分区表和分桶表的主要内容,如果未能解决你的问题,请参考以下文章