文章目录
- 1. Hive 数据库
- 2. 修改数据库
- 3. 创建表
- 3.1 管理表
- 3.2 外部表
- 4. 分区表、管理表
- 5. 删除表
- 6. 修改表
学习自《Hive编程指南》
1. Hive 数据库
create database DBname;
hive (default)> show databases;
OK
default
hive
Time taken: 0.023 seconds, Fetched: 2 row(s)
hive (default)> create database students;
OK
Time taken: 0.066 seconds
hive (default)> show databases;
OK
default
hive
students
Time taken: 0.016 seconds, Fetched: 3 row(s)
create database if not exists students;如果存在同名的表，不会报错（对于连续执行很有用，不会中断）
hive (default)> create database students;
FAILED: Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.DDLTask. Database students already exists
hive (default)> create database if not exists students;
OK
Time taken: 0.016 seconds
show databases like "s.*";搜索以 xxx 开头的数据库
hive (default)> show databases like "s.*";
OK
students
-
hive (default)> dfs -ls -R /;查看数据库在hadoop中的位置 -
自定义hadoop路径
location '/mydb';
hive (default)> create database test> location '/mydb';
- 创建注释
comment "注释字符串 just test comment!";
hive (default)> create database test1> comment "just test comment!";
OK
Time taken: 0.06 secondshive (default)> describe database test1;
OK
test1 just test comment! hdfs://localhost:9000/user/hive/warehouse/test1.db hadoop USER
Time taken: 0.018 seconds, Fetched: 1 row(s)
- 增加相关键值对
with dbproperties ('created'="michael", "date"='2021-04-06') describe database extended test2;显示附件键值对信息
hive (default)> create database test2> with dbproperties ('created'="michael", "date"='2021-04-06');
OK
Time taken: 0.728 secondshive (default)> describe database extended test2;
OK
test2 hdfs://localhost:9000/user/hive/warehouse/test2.db hadoop USER {date=2021-04-06, created=michael}
Time taken: 0.022 seconds, Fetched: 1 row(s)
- 切换数据库
use 数据库名
hive (default)> show databases;
OK
default
hive
students
test
test1
test2
Time taken: 0.641 seconds, Fetched: 6 row(s)hive (default)> use students;
OK
Time taken: 0.027 seconds
hive (students)>
注：cmd里显示数据库名，需要 vim /usr/local/hive/bin/.hiverc
添加 set hive.cli.print.current.db=true;
- 删除数据库
drop database if exists test2数据库名;
2. 修改数据库
hive (default)> alter database student set dbproperties('created by'='Michael ming');hive (default)> describe database extended student;
student hdfs://localhost:9000/user/hive/warehouse/student.db hadoop USER {created by=Michael ming}hive (default)> alter database student set dbproperties('created by'='Michael haha');hive (default)> describe database extended student;
student hdfs://localhost:9000/user/hive/warehouse/student.db hadoop USER {created by=Michael haha}
3. 创建表
hive (default)> create table if not exists employees(> name string comment "employee name",> salary float comment "employee salary",> subordinates array<string> comment "name of subordinates",> deductions map<string, float> comment "key is name, value is percentages",> address struct<street:string, city:string, state:string, zip:int> comment "home address")> comment "info of employees"> location '/employees'> tblproperties('created_by'='michael ming', 'created_at'='2021-04-06 20:00:00');
OK
Time taken: 0.344 secondshive (default)> show tables;
OK
employee
employees
student1
Time taken: 0.057 seconds, Fetched: 3 row(s)
- 显示 表属性
show tblproperties employees;
hive (default)> show tblproperties employees;
OK
comment info of employees
created_at 2021-04-06 20:00:00
created_by michael ming
transient_lastDdlTime 1617710228
Time taken: 0.093 seconds, Fetched: 4 row(s)
- 复制表的模式，不拷贝数据
like 要复制的表名
hive (default)> create table if not exists employees1> like employees;
OK
Time taken: 0.193 secondshive (default)> show tables;
OK
employees
employees1
student1
Time taken: 0.022 seconds, Fetched: 3 row(s)
- 过滤查找
hive (default)> show tables "emp.*";
OK
employees
employees1
- 展示表的结构信息 extended，formatted （更常用）
describe formatted employees;
hive (default)> describe extended employees;
OK
name string employee name
salary float employee salary
subordinates array<string> name of subordinates
deductions map<string,float> key is name, value is percentages
address struct<street:string,city:string,state:string,zip:int> home address Detailed Table Information Table(tableName:employees, dbName:default, owner:hadoop, createTime:1617710228, lastAccessTime:0, retention:0, sd:StorageDescriptor(cols:[FieldSchema(name:name, type:string, comment:employee name), FieldSchema(name:salary, type:float, comment:employee salary), FieldSchema(name:subordinates, type:array<string>, comment:name of subordinates), FieldSchema(name:deductions, type:map<string,float>, comment:key is name, value is percentages), FieldSchema(name:address, type:struct<street:string,city:string,state:string,zip:int>, comment:home address)], location:hdfs://localhost:9000/employees, inputFormat:org.apache.hadoop.mapred.TextInputFormat, outputFormat:org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat, compressed:false, numBuckets:-1, serdeInfo:SerDeInfo(name:null, serializationLib:org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, parameters:{serialization.format=1}), bucketCols:[], sortCols:[], parameters:{}, skewedInfo:SkewedInfo(skewedColNames:[], skewedColValues:[], skewedColValueLocationMaps:{}), storedAsSubDirectories:false), partitionKeys:[], parameters:{transient_lastDdlTime=1617710228, created_at=2021-04-06 20:00:00, comment=info of employees, created_by=michael ming}, viewOriginalText:null, viewExpandedText:null, tableType:MANAGED_TABLE)
Time taken: 0.746 seconds, Fetched: 7 row(s)hive (default)> describe formatted employees;
OK
# col_name data_type comment name string employee name
salary float employee salary
subordinates array<string> name of subordinates
deductions map<string,float> key is name, value is percentages
address struct<street:string,city:string,state:string,zip:int> home address # Detailed Table Information
Database: default
Owner: hadoop
CreateTime: Tue Apr 06 19:57:08 CST 2021
LastAccessTime: UNKNOWN
Retention: 0
Location: hdfs://localhost:9000/employees
Table Type: MANAGED_TABLE
Table Parameters: comment info of employees created_at 2021-04-06 20:00:00 created_by michael ming transient_lastDdlTime 1617710228 # Storage Information
SerDe Library: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe
InputFormat: org.apache.hadoop.mapred.TextInputFormat
OutputFormat: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat
Compressed: No
Num Buckets: -1
Bucket Columns: []
Sort Columns: []
Storage Desc Params: serialization.format 1
Time taken: 0.069 seconds, Fetched: 32 row(s)
3.1 管理表
也叫内部表，删除管理表时，数据也会被删除
3.2 外部表
删除外部表 external，只会删除表的元信息，不会删除数据
hive (default)> create external table if not exists extstudent(> id int,> name string,> sex string,> age int,> course string)> row format delimited fields terminated by '\t'> location '/home/hadoop/workspace/student.txt';
OK
hive (default)> load data local inpath '/home/hadoop/workspace/student.txt' overwrite into table extstudent;
Loading data to table default.extstudent
OK
Time taken: 1.117 secondshive (default)> select * from extstudent;
OK
1 michael male 18 bigdata
2 ming male 19 AI
3 lili female 18 math
4 huahua female 20 AI
Time taken: 0.768 seconds, Fetched: 4 row(s)
- 输入
describe formatted extstudent;，显示有Table Type: EXTERNAL_TABLE外部表
4. 分区表、管理表
分区用来水平分散压力，提高查询速度 partitioned by
hive (default)> create table stu(> id int,> name string)> partitioned by (country string, sex string)> row format delimited fields terminated by '\t';
OK
Time taken: 0.041 secondshive (default)> load data local inpath '/home/hadoop/workspace/student.txt' overwrite into table stu partition(country='china', sex='male');
Loading data to table default.stu partition (country=china, sex=male)
OK
Time taken: 0.294 seconds
hive (default)> select * from stu;
OK
1 michael china male
2 ming china male
3 lili china male
4 huahua china male
Time taken: 0.069 seconds, Fetched: 4 row(s)
# dfs -ls -R / 显示文件
drwxr-xr-x - hadoop supergroup 0 2021-04-06 22:50 /user/hive/warehouse/stu
drwxr-xr-x - hadoop supergroup 0 2021-04-06 22:50 /user/hive/warehouse/stu/country=china
drwxr-xr-x - hadoop supergroup 0 2021-04-06 22:50 /user/hive/warehouse/stu/country=china/sex=male
-rwxr-xr-x 1 hadoop supergroup 114 2021-04-06 22:50 /user/hive/warehouse/stu/country=china/sex=male/student.txt
- 展示分区
show partitions
hive (default)> show partitions stu;
OK
country=china/sex=male
Time taken: 0.075 seconds, Fetched: 1 row(s)
set hive.mapred.mode=strict;严格模式，需要带where过滤才行，避免超大的查询任务
hive (default)> set hive.mapred.mode=strict;
hive (default)> select * from stu;
FAILED: SemanticException Queries against partitioned tables without a partition filter are disabled for safety reasons. If you know what you are doing, please make sure that hive.strict.checks.large.query is set to false and that hive.mapred.mode is not set to 'strict' to enable them. No partition predicate for Alias "stu" Table "stu"
hive (default)> select * from stu where country='china';
OK
1 michael china male
2 ming china male
3 lili china male
4 huahua china male
Time taken: 0.402 seconds, Fetched: 4 row(s)
set hive.mapred.mode=nonstrict;不严格模式
hive (default)> set hive.mapred.mode=nonstrict;
hive (default)> select * from stu;
OK
1 michael china male
2 ming china male
3 lili china male
4 huahua china male
Time taken: 0.077 seconds, Fetched: 4 row(s)
- 只查看指定分区
hive (default)> show partitions stu partition(country='china');
OK
country=china/sex=male
describe formatted stu;也会显示分区信息
hive (default)> describe formatted stu;
OK
# col_name data_type comment id int
name string # Partition Information
# col_name data_type comment country string
sex string
省略。。。
- 添加分区
alter table stu add partition(country='china1', sex='female');
5. 删除表
drop table if exists 表名;
6. 修改表
使用 alter table 语句，会修改元数据，但不会修改数据本身
- 重命名 表
hive (default)> alter table stu rename to stu_new;
- 增加多个分区
hive (default)> alter table stu_new add if not exists> partition(country='USA', sex='male')> partition(country='RUS', sex='male');hive (default)> show partitions stu_new;
country=RUS/sex=male
country=USA/sex=male
country=china/sex=male
country=china1/sex=female
- 修改分区路径
hive (default)> alter table stu_new partition(country='china', sex='male')> set location "/user/hive/warehouse/mypath";
- 删除分区
hive (default)> alter table stu_new drop if exists partition(country='USA',sex='male');
Dropped the partition country=USA/sex=male
OK
Time taken: 0.404 seconds
- 修改列信息
hive (default)> alter table stu_new> change column id new_id int> comment "changed new_id";
hive (default)> describe stu_new;
OK
new_id int changed new_id
name string
country string
sex string # Partition Information
# col_name data_type comment country string
sex string
还可以修改字段位置 追加 after 字段 或者 first，请同时修改数据以匹配
- 增加列
在分区字段之前，增加新的字段到已有字段之后
hive (default)> alter table stu_new add columns(> height int comment "height of people",> hobby string comment "likes things");
OK
Time taken: 0.074 seconds
hive (default)> describe stu_new;
OK
new_id1 float changed new_id1 float
name string
height int height of people
hobby string likes things
country string
sex string # Partition Information
# col_name data_type comment country string
sex string
- 删除、替换列
replace columns
下面例子移除了之前所有的字段，并指定新的字段：
hive (default)> alter table stu_new replace columns(> c1 float comment "column 1",> c2 string,> c3 float comment 'column 3');hive (default)> describe stu_new;
OK
c1 float column 1
c2 string
c3 float column 3
country string
sex string # Partition Information
# col_name data_type comment country string
sex string
注意：需要数据类型兼容（原来是float ，不能改为 int）
- 修改表属性
增加或修改属性，但无法删除属性
hive (default)> show tblproperties stu_new;
last_modified_by hadoop
last_modified_time 1617749844
transient_lastDdlTime 1617749844hive (default)> alter table stu_new set tblproperties(> 'creator' = 'michael',> 'ok' = 'good');hive (default)> show tblproperties stu_new;
creator michael
last_modified_by hadoop
last_modified_time 1617750323
ok good
transient_lastDdlTime 1617750323hive (default)> alter table stu_new set tblproperties(> 'creator' = 'ming');hive (default)> show tblproperties stu_new;
creator ming
last_modified_by hadoop
last_modified_time 1617750355
ok good
transient_lastDdlTime 1617750355
- 修改存储属性
修改文件格式
hive (default)> alter table stu_new> set fileformat textfile;hive (default)> alter table stu_new> partition(country='china', sex='male')> set fileformat sequencefile;
修改 Serde，并指定属性
hive (default)> alter table stu_new> set serde 'com.example.mySerDe' # 不改，就不需要这句> with serdeproperties(> 'prop1'='v1',> 'prop2'='v2');
FAILED: Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.DDLTask. at least one column must be specified for the table
修改存储属性
hive (default)> alter table stu_new> clustered by (c1, c2)> sorted by (c3) # 可选> into 5 buckets;
- 其他修改表语句
在 hive 之外文件被修改了，就会触发”钩子“的执行？？？
hive (default)> alter table stu_new touch> partition(country='china', sex='male');
hive -e "alter table stu_new touch partition(country='china', sex='male');"
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