Hive 浅谈DDL语法

前言

Hive 不存储数据，是表到HDFS文件的映射关系。在HQL开发中，我们主要关注语法，今天就带着小伙伴们来了解一下每个 DDL 语句的语义。

1. 数据库

1.1 查询所有数据库

SHOW DATABASES;

1.2 创建库

CREATE [REMOTE] (DATABASE|SCHEMA) [IF NOT EXISTS] database_name
  [COMMENT database_comment]
  [LOCATION hdfs_path]
  [MANAGEDLOCATION hdfs_path]
  [WITH DBPROPERTIES (property_name=property_value, ...)];

• REMOTE 也是在Hive 4.0.0 版本中添加的，主要是为了与其他系统建立数据连接使用的。
• DATABASE 和 SCHEMA可以互换，语义一样。
• IF NOT EXISTS：表示如果库名为database_name的数据库不存在的情况下创建；如果存在，就不再创建。
• MANAGEDLOCATION是在 Hive 4.0.0 版本中添加的。LOCATION现在指的是外部表的默认目录，MANAGEDLOCATION指的是内部表的默认路径。建议MANAGEDLOCATION位于metastore.warehouse.dir中，这样所有被管理的表在同一个根目录下，便于使用统一管理策略。另外，还可以与metastore.warehouse.tenant.colocation一起使用，使其指向仓库根目录之外的目录，以具有基于租户的公共根目录，在该目录中可以设置配额和其他策略。
• WITH DBPROPERTIES：用来添加配置项

注意：[] 包裹的语句是可选项，()包裹的语句是必选项！

1.3 修改库

• 更新配置项：

ALTER (DATABASE|SCHEMA) database_name SET DBPROPERTIES (property_name=property_value, ...);

• 更新 Owner：

ALTER (DATABASE|SCHEMA) database_name SET OWNER [USER|ROLE] user_or_role;

• 更新 Location

ALTER (DATABASE|SCHEMA) database_name SET LOCATION fs_path;

1.4 删除库

DROP (DATABASE|SCHEMA) [IF EXISTS] database_name [RESTRICT|CASCADE];

• RESTRICT是默认值，如果数据库不为null，会删除失败。

1.5 use库

进入database_name数据库：

USE database_name;

2. 表

2.1 查看所有表

SHOW TABLES;

2.2 创建表

CREATE [TEMPORARY] [EXTERNAL] TABLE [IF NOT EXISTS] [db_name.]table_name    -- (Note: TEMPORARY available in Hive 0.14.0 and later)
  [(col_name data_type [column_constraint_specification] [COMMENT col_comment], ... [constraint_specification])]
  [COMMENT table_comment]
  [PARTITIONED BY (col_name data_type [COMMENT col_comment], ...)]
  [CLUSTERED BY (col_name, col_name, ...) [SORTED BY (col_name [ASC|DESC], ...)] INTO num_buckets BUCKETS]
  [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)
  ]
  [LOCATION hdfs_path]
  [TBLPROPERTIES (property_name=property_value, ...)]   -- (Note: Available in Hive 0.6.0 and later)
  [AS select_statement];   -- (Note: 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];
 
data_type
  : primitive_type
  | array_type
  | map_type
  | struct_type
  | union_type  -- (Note: Available in Hive 0.7.0 and later)
 
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)
 
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)
 
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)
  | JSONFILE    -- (Note: Available in Hive 4.0.0 and later)
  | INPUTFORMAT input_format_classname OUTPUTFORMAT output_format_classname
 
column_constraint_specification:
  : [ PRIMARY KEY|UNIQUE|NOT NULL|DEFAULT [default_value]|CHECK  [check_expression] ENABLE|DISABLE NOVALIDATE RELY/NORELY ]
 
default_value:
  : [ LITERAL|CURRENT_USER()|CURRENT_DATE()|CURRENT_TIMESTAMP()|NULL ] 
 
constraint_specification:
  : [, PRIMARY KEY (col_name, ...) DISABLE NOVALIDATE RELY/NORELY ]
    [, PRIMARY KEY (col_name, ...) DISABLE NOVALIDATE RELY/NORELY ]
    [, CONSTRAINT constraint_name FOREIGN KEY (col_name, ...) REFERENCES table_name(col_name, ...) DISABLE NOVALIDATE 
    [, CONSTRAINT constraint_name UNIQUE (col_name, ...) DISABLE NOVALIDATE RELY/NORELY ]
    [, CONSTRAINT constraint_name CHECK [check_expression] ENABLE|DISABLE NOVALIDATE RELY/NORELY ]

注意：由于创建表涉及的内容比较多，会单独拿出来另写一篇文章详细介绍的！

2.3 修改表

• 重命名：

ALTER TABLE table_name RENAME TO new_table_name;

• 更新配置项：

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

• 更新 Location：

ALTER TABLE table_name [PARTITION partition_spec] SET LOCATION fs_path;

注意：当添加PARTITION partition_spec时，该操作将应用于相应的分区，而不是表（下同）。

• 更新文件格式：

ALTER TABLE table_name [PARTITION partition_spec] SET FILEFORMAT file_format;

• 更新 SerDe 配置项：

ALTER TABLE table_name [PARTITION partition_spec] SET SERDE serde_class_name [WITH SERDEPROPERTIES serde_properties];

ALTER TABLE table_name [PARTITION partition_spec] SET SERDEPROPERTIES serde_properties;

serde_properties:
  : (property_name = property_value, property_name = property_value, ... )

• 添加分区：

ALTER TABLE table_name ADD [IF NOT EXISTS] (PARTITION partition_spec [LOCATION fs_path])+;

• 删除分区：

ALTER TABLE table_name DROP [IF EXISTS] PARTITION partition_spec[, PARTITION partition_spec, ...];

• 添加/替换列：

ALTER TABLE table_name
  ADD|REPLACE COLUMNS (col_name data_type [COMMENT col_comment], ...)
  [CASCADE|RESTRICT]

• 修改列：

ALTER TABLE table_name CHANGE [COLUMN] col_old_name col_new_name column_type
  [COMMENT col_comment] [FIRST|AFTER column_name] [CASCADE|RESTRICT];

2.4 删除表

DROP TABLE [IF EXISTS] table_name;

3. 视图

3.1 创建视图

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

3.2 修改视图

• 重命名：

ALTER VIEW view_name RENAME TO new_view_name;

• 更新配置项：

ALTER VIEW view_name SET TBLPROPERTIES (property_name = property_value, ... );

• 更新查询语句：

ALTER VIEW view_name AS select_statement;

3.3 删除视图

DROP VIEW [IF EXISTS] view_name;

4. 函数

4.1 查看所有函数

SHOW FUNCTIONS;

4.2 创建函数

CREATE FUNCTION function_name AS class_name;

4.3 删除函数

DROP FUNCTION [IF EXISTS] function_name;