HiveQL： 数据定义

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;

代码语言：javascript复制

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）

代码语言：javascript复制

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

代码语言：javascript复制

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';

代码语言：javascript复制

hive (default)> create database test
              > location '/mydb';

• 创建注释 comment "注释字符串 just test comment!";

代码语言：javascript复制

hive (default)> create database test1
              > comment "just test comment!";
OK
Time taken: 0.06 seconds

hive (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

代码语言：javascript复制

hive (default)> create database test2
              > with dbproperties ('created'="michael", "date"='2021-04-06');
OK
Time taken: 0.728 seconds

hive (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

代码语言：javascript复制

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

代码语言：javascript复制

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

代码语言：javascript复制

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 seconds

hive (default)> show tables;
OK
employee
employees
student1
Time taken: 0.057 seconds, Fetched: 3 row(s)

• 显示 表属性 show tblproperties employees;

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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

代码语言：javascript复制

hive (default)> create table if not exists employees1
              > like employees;
OK
Time taken: 0.193 seconds

hive (default)> show tables;
OK
employees
employees1
student1
Time taken: 0.022 seconds, Fetched: 3 row(s)

• 过滤查找

代码语言：javascript复制

hive (default)> show tables "emp.*";
OK
employees
employees1

• 展示表的结构信息 extended，formatted （更常用）describe formatted employees;

代码语言：javascript复制

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

代码语言：javascript复制

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

代码语言：javascript复制

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 seconds

hive (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

代码语言：javascript复制

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 seconds

hive (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)

代码语言：javascript复制

# 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

代码语言：javascript复制

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

代码语言：javascript复制

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

代码语言：javascript复制

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

代码语言：javascript复制

hive (default)> show partitions stu partition(country='china');
OK
country=china/sex=male

• describe formatted stu; 也会显示分区信息

代码语言：javascript复制

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

代码语言：javascript复制

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

代码语言：javascript复制

hive (default)> alter table stu rename to stu_new;

• 增加多个分区

代码语言：javascript复制

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

代码语言：javascript复制

hive (default)> alter table stu_new partition(country='china', sex='male')
              > set location "/user/hive/warehouse/mypath";

• 删除分区

代码语言：javascript复制

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

代码语言：javascript复制

hive (default)> alter table stu_new
              > change column id new_id int
              > comment "changed new_id";

代码语言：javascript复制

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

代码语言：javascript复制

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：

代码语言：javascript复制

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

代码语言：javascript复制

hive (default)> show tblproperties stu_new;
last_modified_by	hadoop
last_modified_time	1617749844
transient_lastDdlTime	1617749844

hive (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	1617750323

hive (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

代码语言：javascript复制

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

代码语言：javascript复制

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

代码语言：javascript复制

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？？？

代码语言：javascript复制

hive (default)> alter table stu_new touch
              > partition(country='china', sex='male');

代码语言：javascript复制

hive -e "alter table stu_new touch partition(country='china', sex='male');"

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