mirror of
https://github.com/apache/sqoop.git
synced 2025-05-08 13:52:25 +08:00
4b193ec488
From: Christopher Douglas <cdouglas@apache.org> git-svn-id: https://svn.apache.org/repos/asf/incubator/sqoop/trunk@1149834 13f79535-47bb-0310-9956-ffa450edef68
69 lines
2.7 KiB
Plaintext
69 lines
2.7 KiB
Plaintext
|
|
////
|
|
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.
|
|
////
|
|
|
|
|
|
Importing Individual Tables
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
In addition to full-database imports, Sqoop will allow you to import
|
|
individual tables. Instead of using +--all-tables+, specify the name of
|
|
a particular table with the +--table+ argument:
|
|
|
|
----
|
|
$ sqoop --connect jdbc:mysql://database.example.com/employees \
|
|
--table employee_names
|
|
----
|
|
|
|
You can further specify a subset of the columns in a table by using
|
|
the +--columns+ argument. This takes a list of column names, delimited
|
|
by commas, with no spaces in between. e.g.:
|
|
|
|
----
|
|
$ sqoop --connect jdbc:mysql://database.example.com/employees \
|
|
--table employee_names --columns employee_id,first_name,last_name,dept_id
|
|
----
|
|
|
|
Sqoop will use a MapReduce job to read sections of the table in
|
|
parallel. For the MapReduce tasks to divide the table space, the
|
|
results returned by the database must be orderable. Sqoop will
|
|
automatically detect the primary key for a table and use that to order
|
|
the results. If no primary key is available, or (less likely) you want
|
|
to order the results along a different column, you can specify the
|
|
column name with +--split-by+.
|
|
|
|
.Row ordering
|
|
IMPORTANT: To guarantee correctness of your input, you must select an
|
|
ordering column for which each row has a unique value. If duplicate
|
|
values appear in the ordering column, the results of the import are
|
|
undefined, and Sqoop will not be able to detect the error.
|
|
|
|
Finally, you can control which rows of a table are imported via the
|
|
+--where+ argument. With this argument, you may specify a clause to be
|
|
appended to the SQL statement used to select rows from the table,
|
|
e.g.:
|
|
|
|
----
|
|
$ sqoop --connect jdbc:mysql://database.example.com/employees \
|
|
--table employee_names --where "employee_id > 40 AND active = 1"
|
|
----
|
|
|
|
The +--columns+, +--split-by+, and +--where+ arguments are incompatible with
|
|
+--all-tables+. If you require special handling for some of the tables,
|
|
then you must manually run a separate import job for each table.
|
|
|