src/contrib/sqoop/doc/export.txt

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Exporting to a Database
-----------------------

In addition to importing database tables into HDFS, Sqoop can also
work in "reverse," reading the contents of a file or directory in
HDFS, interpreting the data as database rows, and inserting them
into a specified database table.

To run an export, invoke Sqoop with the +--export-dir+ and
+--table+ options. e.g.:

----
$ sqoop --connect jdbc:mysql://db.example.com/foo --table bar  \
    --export-dir /results/bar_data
----

This will take the files in +/results/bar_data+ and inject their
contents in to the +bar+ table in the +foo+ database on +db.example.com+.
The target table must already exist in the database. Sqoop will perform
a set of +INSERT INTO+ operations, without regard for existing content. If
Sqoop attempts to insert rows which violate constraints in the database
(e.g., a particular primary key value already exists), then the export
will fail.

As in import mode, Sqoop will auto-generate an interoperability class
to use with the particular table in question. This will be used to parse
the records in HDFS files before loading their contents into the database.
You must specify the same delimiters (e.g., with +--fields-terminated-by+,
etc.) as are used in the files to export in order to parse the data
correctly. If your data is stored in SequenceFiles (created with an import
in the +--as-sequencefile+ format), then you do not need to specify
delimiters.

If you have an existing auto-generated jar and class that you intend to use
with Sqoop, you can specify these with the +--jar-file+ and +--class-name+
parameters. Providing these options will disable autogeneration of a new
class based on the target table.