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hive 学习系列三(表格的创建create-table)

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表格创建:

语法

第一种建表的形式:

说明: 
temporary 临时表,在当前回话内,这张表有效,当回话结束,可以理解为程序结束,则程序终止。
external 外部表, hdfs 上的表的文件,并非存储在默认的路径上的时候, 
    EXTERNAL 表格和正常表格删除区别,external 只删除metastore
    可以称为外部表,便于和其他数据库和程序交互,比如impala 等。
如果不加 IF NOT EXISTS 的时候,如果表存在,会报错,可以加上IF NOT EXISTS 加以避免。
注意表名不区分大小写
例子:
create temporary table my.table1;
create external table my.table2;
create tabel if not exists my.table3;
-- (Note: TEMPORARY available in Hive 0.14.0 and later)
CREATE [TEMPORARY] [EXTERNAL] TABLE [IF NOT EXISTS] [db_name.]table_name    
   --定义列, 比如 id  Int comment ‘索引‘, name string comment ‘名字‘
  [(col_name data_type [COMMENT col_comment], ... [constraint_specification])]   
  [COMMENT table_comment]  -- comment 表示表的注释    
  --分区,括号内的定义类似列的定义,分区可以根据默写字段比如日期,城市,进行分区,可以加快某些条件下的查询
  --部分列的集合,根据分区列的进行粗粒度的划分,一个分区,代表着一个目录
  [PARTITIONED BY (col_name data_type [COMMENT col_comment], ...)]  
  --分桶,在分区的基础上,可以进行分桶,分桶的原理是,根据某几列进行计算hash 值,
  --然后hash 值对分成的桶的个数取余操作,决定放在哪个桶里面
  --在数据量足够大的情况下,分桶比分区,更高的查询效率 
  --分桶,还可以使抽样更加高效
  [CLUSTERED BY (col_name, col_name, ...) 
            [SORTED BY (col_name [ASC|DESC], ...)] INTO num_buckets BUCKETS]  ---- 分桶
  ---大致上Skewed,对数据倾斜处理有很大帮助,没用过 
  [SKEWED BY (col_name, col_name, ...)                  -- (Note: Available in Hive 0.10.0 and later)]
     ON ((col_value, col_value, ...), (col_value, col_value, ...), ...)
     [STORED AS DIRECTORIES]
  [
   [ROW FORMAT row_format] 
   [STORED AS file_format]
     | STORED BY ‘storage.handler.class.name‘ [WITH SERDEPROPERTIES (...)]  -- (Note: Available in Hive 0.6.0 and later)
  ]   -- 表示文件的存储格式, 其中store by 指的是自定义文件格式,用得不多,笔者没有用过。
  [LOCATION hdfs_path]
  [TBLPROPERTIES (property_name=property_value, ...)]    --  表示表格的附加属性和表述。 
                                                         -- (Note: Available in Hive 0.6.0 and later)
  [AS select_statement];  
   -- 建立表格的时候同时从其他表格select 数据进行填充表格。
   -- (Note: as  select_statement Available in Hive 0.5.0 and later; not supported for external tables)
 
CREATE [TEMPORARY] [EXTERNAL] TABLE [IF NOT EXISTS] [db_name.]table_name
  LIKE existing_table_or_view_name
  [LOCATION hdfs_path];
 
 说明:
 数据类型
data_type
  : primitive_type
  | array_type
  | map_type
  | struct_type
  | union_type  -- (Note: Available in Hive 0.7.0 and later)
 
基本数据类型
primitive_type
  : TINYINT
  | SMALLINT
  | INT
  | BIGINT
  | BOOLEAN
  | FLOAT
  | DOUBLE
  | DOUBLE PRECISION -- (Note: Available in Hive 2.2.0 and later)
  | STRING
  | BINARY      -- (Note: Available in Hive 0.8.0 and later)
  | TIMESTAMP   -- (Note: Available in Hive 0.8.0 and later)
  | DECIMAL     -- (Note: Available in Hive 0.11.0 and later)
  | DECIMAL(precision, scale)  -- (Note: Available in Hive 0.13.0 and later)
  | DATE        -- (Note: Available in Hive 0.12.0 and later)
  | VARCHAR     -- (Note: Available in Hive 0.12.0 and later)
  | CHAR        -- (Note: Available in Hive 0.13.0 and later)
 
 复杂数据类型
array_type
  : ARRAY < data_type >
 
map_type
  : MAP < primitive_type, data_type >
 
struct_type
  : STRUCT < col_name : data_type [COMMENT col_comment], ...>
 
union_type
   : UNIONTYPE < data_type, data_type, ... >  -- (Note: Available in Hive 0.7.0 and later)
 
## 在hdfs 上的文件存储格式
row_format
  : DELIMITED [FIELDS TERMINATED BY char [ESCAPED BY char]] [COLLECTION ITEMS TERMINATED BY char]
        [MAP KEYS TERMINATED BY char] [LINES TERMINATED BY char]
        [NULL DEFINED AS char]   -- (Note: Available in Hive 0.13 and later)
  | SERDE serde_name [WITH SERDEPROPERTIES (property_name=property_value, property_name=property_value, ...)]
 
file_format:
  : SEQUENCEFILE
  | TEXTFILE    -- (Default, depending on hive.default.fileformat configuration)
  | RCFILE      -- (Note: Available in Hive 0.6.0 and later)
  | ORC         -- (Note: Available in Hive 0.11.0 and later)
  | PARQUET     -- (Note: Available in Hive 0.13.0 and later)
  | AVRO        -- (Note: Available in Hive 0.14.0 and later)
  | INPUTFORMAT input_format_classname OUTPUTFORMAT output_format_classname
 
constraint_specification:
  : [, PRIMARY KEY (col_name, ...) DISABLE NOVALIDATE ]
    [, CONSTRAINT constraint_name FOREIGN KEY (col_name, ...) REFERENCES table_name(col_name, ...) DISABLE NOVALIDATE 

说明

上述的建表语法,有些语法笔者不是很懂,希望各位不吝赐教。

常见例子:

例子一

create  table my.tabelDemo(
    id      int,
    name    string,
    hobby   array<string>,
   add     map<String,string>,
)
row format delimited
fields terminated by ‘,‘
collection items terminated by ‘-‘
map keys terminated by ‘:‘
store as textfile;

每一列之间,使用逗号分隔,
array 内部的string 使用-分隔。
map 的key 和value, 使用冒号分隔 :

例子二

-- 文件存储形式是parquet
CREATE EXTERNAL TABLE IF NOT EXISTS default.person_table( 
    ftpurl        string, 
    ipcid         string, 
    feature       array<float>, 
    eyeglasses    int, 
    gender        int, 
    haircolor     int, 
    hairstyle     int, 
    hat           int, 
    huzi          int, 
    tie           int, 
    timeslot      int, 
    exacttime     Timestamp, 
    searchtype    string, 
    sharpness     int
) 
partitioned by (date string) 
STORED AS PARQUET 
LOCATION ‘/user/hive/warehouse/person_table‘;

struct 使用

create table student_test(id INT, info struct<name:STRING, age:INT>)  
    ROW FORMAT DELIMITED FIELDS TERMINATED BY ‘,‘                         
    COLLECTION ITEMS TERMINATED BY ‘:‘;         
    
hdfs 中的文件数据格式大致是:即(struct 里面对应的分隔符是 collection items terminated by 指定的分隔符)
1,zhou:30  
2,yan:30  
3,chen:20  
4,li:80  

以下是truncate 用来进行表格的清空

一个有用的数据清空工具

TRUNCATE TABLE table_name [PARTITION partition_spec];
 
partition_spec:
  : (partition_column = partition_col_value, partition_column = partition_col_value, ...)

删除表格

DROP TABLE [IF EXISTS] table_name [PURGE]; 
-- purge,如果配置了垃圾回收,而drop table 时 加上了purge,则其会被彻底删除,在垃圾箱中也找不回来。

修改表

重命名表

ALTER TABLE table_name RENAME TO new_table_name;

改变表格属性

ALTER TABLE table_name SET TBLPROPERTIES table_properties;
 
table_properties:
  : (property_name = property_value, property_name = property_value, ... )

改变表格评论

ALTER TABLE table_name SET TBLPROPERTIES (‘comment‘ = new_comment);

对表格进行分桶

ALTER TABLE table_name CLUSTERED BY (col_name, col_name, ...) [SORTED BY (col_name, ...)]
  INTO num_buckets BUCKETS;

添加分区

ALTER TABLE table_name ADD [IF NOT EXISTS] PARTITION partition_spec [LOCATION ‘location‘]
    [, PARTITION partition_spec [LOCATION ‘location‘], ...];
partition_spec:
  : (partition_column = partition_col_value, partition_column = partition_col_value, ...)

重命名分区

ALTER TABLE table_name PARTITION partition_spec RENAME TO PARTITION partition_spec;

删除分区

ALTER TABLE table_name DROP [IF EXISTS] PARTITION partition_spec[, PARTITION partition_spec, ...]
  [IGNORE PROTECTION] [PURGE];            
  -- (Note: PURGE available in Hive 1.2.0 and later, IGNORE PROTECTION not available 2.0.0 and later)

视图创建

CREATE VIEW [IF NOT EXISTS] [db_name.]view_name [(column_name [COMMENT column_comment], ...) ]
  [COMMENT view_comment]
  [TBLPROPERTIES (property_name = property_value, ...)]
  AS SELECT ...;

原文参考:
https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL

hive 学习系列三(表格的创建create-table)

标签:sorted   desc   dir   config   storage   文件格式   not   efi   isp   

原文地址:https://www.cnblogs.com/unnunique/p/9362094.html

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