Create a table
1. To build the table syntax
CREATE [EXTERNAL] TABLE [IF NOT EXISTS] table_name
[(col_name data_type [COMMENT col_comment], ...)]
[HOW 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]
[ROW FORMAT row_format]
[STORED AS file_format]
[LOCATION hdfs_path]
2. Field explanations
(1) CREATE TABLE creates a table name is specified. If the same table name already exists, an exception is thrown; the user can use IF NOT EXISTS option to ignore this exception.
When (2) EXTERNAL keyword allows the user to create an external table, while construction of the table to specify a path to the actual data points (LOCATION), Hive create an internal table, will move to the path of the data warehouse data points; if you create an external table, only records where the data path, the location does not make any changes to the data. Delete table, the metadata of internal tables and data will be deleted together, and external table only remove metadata, do not delete the data.
(3) COMMENT: add comments to tables and columns.
(4) PARTITIONED BY create a partition table
(5) CLUSTERED BY create a sub-bucket table
(6) SORTED BY not used
（7）ROW FORMAT
DELIMITED [FIELDS TERMINATED BY char] [COLLECTION ITEMS TERMINATED BY char]
[MAP KEYS TERMINATED BY char] [LINES TERMINATED BY char]
| SERDE serde_name [WITH SERDEPROPERTIES (property_name=property_value, property_name=property_value, ...)]
When users can build custom SerDe table or use the built-in SerDe. If you do not specify ROW FORMAT or ROW FORMAT DELIMITED, will use its own SerDe. In the construction of the table, the user also needs to specify the column of the table, while users listed in the specified table also specify custom SerDe, Hive table determined by a particular data string SerDe.
SerDe is Serialize / Deserilize short, intended for serialization and deserialization.
(8) STORED AS designated storage file type
Common store file types: SEQUENCEFILE (binary sequence file), TEXTFILE (text), RCFILE (columnar storage format)
If the data file is plain text, you can use STORED AS TEXTFILE. If you need to compress data using STORED AS SEQUENCEFILE.
(9) LOCATION: Specifies the location table is stored in the HDFS.
(10) LIKE allows the user to copy an existing table structure, but does not copy the data.
The above article content from "Monkey Wisdom Education": www.wukongone.com, "Wukong wisdom education" is a professional video teaching large data network, exclusive tailor your future.