### What changes were proposed in this pull request? Remove the unneeded embedded inline HTML markup by using the basic markdown syntax. Please see #28414 ### Why are the changes needed? Make the doc cleaner and easily editable by MD editors. ### Does this PR introduce _any_ user-facing change? No ### How was this patch tested? Manually build and check Closes #28451 from huaxingao/html_cleanup. Authored-by: Huaxin Gao <huaxing@us.ibm.com> Signed-off-by: Sean Owen <srowen@gmail.com>
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layout | title | displayTitle | license |
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global | CREATE DATASOURCE TABLE | CREATE DATASOURCE TABLE | Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. |
Description
The CREATE TABLE
statement defines a new table using a Data Source.
Syntax
CREATE TABLE [ IF NOT EXISTS ] table_identifier
[ ( col_name1 col_type1 [ COMMENT col_comment1 ], ... ) ]
[ USING data_source ]
[ OPTIONS ( key1=val1, key2=val2, ... ) ]
[ PARTITIONED BY ( col_name1, col_name2, ... ) ]
[ CLUSTERED BY ( col_name3, col_name4, ... )
[ SORTED BY ( col_name [ ASC | DESC ], ... ) ]
INTO num_buckets BUCKETS ]
[ LOCATION path ]
[ COMMENT table_comment ]
[ TBLPROPERTIES ( key1=val1, key2=val2, ... ) ]
[ AS select_statement ]
Note that, the clauses between the USING clause and the AS SELECT clause can come in as any order. For example, you can write COMMENT table_comment after TBLPROPERTIES.
Parameters
-
table_identifier
Specifies a table name, which may be optionally qualified with a database name.
Syntax:
[ database_name. ] table_name
-
USING data_source
Data Source is the input format used to create the table. Data source can be CSV, TXT, ORC, JDBC, PARQUET, etc.
-
PARTITIONED BY
Partitions are created on the table, based on the columns specified.
-
CLUSTERED BY
Partitions created on the table will be bucketed into fixed buckets based on the column specified for bucketing.
NOTE: Bucketing is an optimization technique that uses buckets (and bucketing columns) to determine data partitioning and avoid data shuffle.
-
SORTED BY
Determines the order in which the data is stored in buckets. Default is Ascending order.
-
LOCATION
Path to the directory where table data is stored, which could be a path on distributed storage like HDFS, etc.
-
COMMENT
A string literal to describe the table.
-
TBLPROPERTIES
A list of key-value pairs that is used to tag the table definition.
-
AS select_statement
The table is populated using the data from the select statement.
Data Source Interaction
A Data Source table acts like a pointer to the underlying data source. For example, you can create a table "foo" in Spark which points to a table "bar" in MySQL using JDBC Data Source. When you read/write table "foo", you actually read/write table "bar".
In general CREATE TABLE is creating a "pointer", and you need to make sure it points to something existing. An exception is file source such as parquet, json. If you don't specify the LOCATION, Spark will create a default table location for you.
For CREATE TABLE AS SELECT, Spark will overwrite the underlying data source with the data of the input query, to make sure the table gets created contains exactly the same data as the input query.
Examples
--Use data source
CREATE TABLE student (id INT, name STRING, age INT) USING CSV;
--Use data from another table
CREATE TABLE student_copy USING CSV
AS SELECT * FROM student;
--Omit the USING clause, which uses the default data source (parquet by default)
CREATE TABLE student (id INT, name STRING, age INT);
--Specify table comment and properties
CREATE TABLE student (id INT, name STRING, age INT) USING CSV
COMMENT 'this is a comment'
TBLPROPERTIES ('foo'='bar');
--Specify table comment and properties with different clauses order
CREATE TABLE student (id INT, name STRING, age INT) USING CSV
TBLPROPERTIES ('foo'='bar')
COMMENT 'this is a comment';
--Create partitioned and bucketed table
CREATE TABLE student (id INT, name STRING, age INT)
USING CSV
PARTITIONED BY (age)
CLUSTERED BY (Id) INTO 4 buckets;