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问题导读：
1、--connect参数作用？
2、使用哪个参数从控制台读取数据库访问密码？
3、Sqoop将关系型数据库表中数据导入HDFS基本参数要求及命令？
4、数据默认导入HDFS文件系统中的路径？
5、--columns参数的作用？
6、--where参数的作用？
一、部分关键参数介绍
参数介绍 --connect <jdbc-uri> 指定关系型数据库JDBC连接字符串 --connection-manager <class-name> 指定数据库使用的管理类 --driver <class-name> 手动指定要使用JDBC驱动程序类 --hadoop-mapred-home <dir> 重写覆盖$HADOOP_MAPRED_HOME --help 使用提示帮助提示 --password-file 设置包含身份验证密码的路径文件 -P 从控制台读取数据库访问密码 --password <password> 设置数据库身份验证密码 --username <username> 设置数据库访问用户 --verbose 打印更多程序执行流程信息 --connection-param-file <filename> 用于提供连接参数的可选的属性文件二、要导出的MySQL数据库
[hadoopUser@secondmgt ~]$ mysql -uhive -phive spice Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 419 Server version: 5.1.73 Source distribution Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> select * from users; +----+----------+----------+-----+---------+------------+-------+------+ | id | username | password | sex | content | datetime | vm_id | isad | +----+----------+----------+-----+---------+------------+-------+------+ | 56 | hua | hanyun | 男 | 开通 | 2013-12-02 | 0 | 1 | | 58 | feng | 123456 | 男 | 开通 | 2013-11-22 | 0 | 0 | | 59 | test | 123456 | 男 | 开通 | 2014-03-05 | 58 | 0 | | 60 | user1 | 123456 | 男 | 开通 | 2014-06-26 | 66 | 0 | | 61 | user2 | 123 | 男 | 开通 | 2013-12-13 | 56 | 0 | | 62 | user3 | 123456 | 男 | 开通 | 2013-12-14 | 0 | 0 | | 64 | kai.zhou | 123456 | ? | ?? | 2014-03-05 | 65 | 0 | +----+----------+----------+-----+---------+------------+-------+------+ 7 rows in set (0.00 sec)
执行导入命令，最少要指定数据库连接字符串、访问用户名、访问密码和要导入的表名，默认情况下会将数据导入到HDFS根目录下的/user/hadoopUser/<表名>/目录下，也可以使用--target-dir参数，指定导入目录。如下：
[hadoopUser@secondmgt ~]$ sqoop import --connect jdbc:mysql://secondmgt:3306/spice --username hive --password hive --table users --target-dir /output/sqoop/
Warning: /usr/lib/hcatalog does not exist! HCatalog jobs will fail.
Please set $HCAT_HOME to the root of your HCatalog installation.
15/01/17 20:28:16 WARN tool.BaseSqoopTool: Setting your password on the command-line is insecure. Consider using -P instead.
15/01/17 20:28:16 INFO manager.MySQLManager: Preparing to use a MySQL streaming resultset.
15/01/17 20:28:16 INFO tool.CodeGenTool: Beginning code generation
15/01/17 20:28:16 INFO manager.SqlManager: Executing SQL statement: SELECT t.* FROM `users` AS t LIMIT 1
15/01/17 20:28:16 INFO manager.SqlManager: Executing SQL statement: SELECT t.* FROM `users` AS t LIMIT 1
15/01/17 20:28:16 INFO orm.CompilationManager: HADOOP_MAPRED_HOME is /home/hadoopUser/cloud/hadoop/programs/hadoop-2.2.0
Note: /tmp/sqoop-hadoopUser/compile/c010e7410ec7339ef9b4d9dc2ddaac80/users.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
15/01/17 20:28:18 INFO orm.CompilationManager: Writing jar file: /tmp/sqoop-hadoopUser/compile/c010e7410ec7339ef9b4d9dc2ddaac80/users.jar
15/01/17 20:28:18 WARN manager.MySQLManager: It looks like you are importing from mysql.
15/01/17 20:28:18 WARN manager.MySQLManager: This transfer can be faster! Use the --direct
15/01/17 20:28:18 WARN manager.MySQLManager: option to exercise a MySQL-specific fast path.
15/01/17 20:28:18 INFO manager.MySQLManager: Setting zero DATETIME behavior to convertToNull (mysql)
15/01/17 20:28:18 INFO mapreduce.ImportJobBase: Beginning import of users
15/01/17 20:28:18 INFO Configuration.deprecation: mapred.job.tracker is deprecated. Instead, use mapreduce.jobtracker.address
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/hadoopUser/cloud/hadoop/programs/hadoop-2.2.0/share/hadoop/common/lib/slf4j-log4j12-1.7.5.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/hadoopUser/cloud/hbase/hbase-0.96.2-hadoop2/lib/slf4j-log4j12-1.6.4.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
15/01/17 20:28:18 INFO Configuration.deprecation: mapred.jar is deprecated. Instead, use mapreduce.job.jar
15/01/17 20:28:19 INFO Configuration.deprecation: mapred.map.tasks is deprecated. Instead, use mapreduce.job.maps
15/01/17 20:28:19 INFO client.RMProxy: Connecting to ResourceManager at secondmgt/192.168.2.133:8032
15/01/17 20:28:20 INFO db.DataDrivenDBInputFormat: BoundingValsQuery: SELECT MIN(`id`), MAX(`id`) FROM `users`
15/01/17 20:28:20 INFO mapreduce.JobSubmitter: number of splits:4
15/01/17 20:28:20 INFO Configuration.deprecation: mapred.job.classpath.files is deprecated. Instead, use mapreduce.job.classpath.files
15/01/17 20:28:20 INFO Configuration.deprecation: user.name is deprecated. Instead, use mapreduce.job.user.name
15/01/17 20:28:20 INFO Configuration.deprecation: mapred.cache.files.filesizes is deprecated. Instead, use mapreduce.job.cache.files.filesizes
15/01/17 20:28:20 INFO Configuration.deprecation: mapred.cache.files is deprecated. Instead, use mapreduce.job.cache.files
15/01/17 20:28:20 INFO Configuration.deprecation: mapred.reduce.tasks is deprecated. Instead, use mapreduce.job.reduces
15/01/17 20:28:20 INFO Configuration.deprecation: mapred.output.value.class is deprecated. Instead, use mapreduce.job.output.value.class
15/01/17 20:28:20 INFO Configuration.deprecation: mapreduce.map.class is deprecated. Instead, use mapreduce.job.map.class
15/01/17 20:28:20 INFO Configuration.deprecation: mapred.job.name is deprecated. Instead, use mapreduce.job.name
15/01/17 20:28:20 INFO Configuration.deprecation: mapreduce.inputformat.class is deprecated. Instead, use mapreduce.job.inputformat.class
15/01/17 20:28:20 INFO Configuration.deprecation: mapred.output.dir is deprecated. Instead, use mapreduce.output.fileoutputformat.outputdir
15/01/17 20:28:20 INFO Configuration.deprecation: mapreduce.outputformat.class is deprecated. Instead, use mapreduce.job.outputformat.class
15/01/17 20:28:20 INFO Configuration.deprecation: mapred.cache.files.timestamps is deprecated. Instead, use mapreduce.job.cache.files.timestamps
15/01/17 20:28:20 INFO Configuration.deprecation: mapred.output.key.class is deprecated. Instead, use mapreduce.job.output.key.class
15/01/17 20:28:20 INFO Configuration.deprecation: mapred.working.dir is deprecated. Instead, use mapreduce.job.working.dir
15/01/17 20:28:21 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1421373857783_0002
15/01/17 20:28:21 INFO impl.YarnClientImpl: Submitted application application_1421373857783_0002 to ResourceManager at secondmgt/192.168.2.133:8032
15/01/17 20:28:21 INFO mapreduce.Job: The url to track the job: http://secondmgt:8088/proxy/application_1421373857783_0002/
15/01/17 20:28:21 INFO mapreduce.Job: Running job: job_1421373857783_0002
15/01/17 20:28:34 INFO mapreduce.Job: Job job_1421373857783_0002 running in uber mode : false
15/01/17 20:28:34 INFO mapreduce.Job: map 0% reduce 0%
15/01/17 20:28:44 INFO mapreduce.Job: map 25% reduce 0%
15/01/17 20:28:49 INFO mapreduce.Job: map 75% reduce 0%
15/01/17 20:28:54 INFO mapreduce.Job: map 100% reduce 0%
15/01/17 20:28:54 INFO mapreduce.Job: Job job_1421373857783_0002 completed successfully
15/01/17 20:28:54 INFO mapreduce.Job: Counters: 27
File System Counters
FILE: Number of bytes read=0
FILE: Number of bytes written=368040
FILE: Number of read operations=0
FILE: Number of large read operations=0
FILE: Number of write operations=0
HDFS: Number of bytes read=401
HDFS: Number of bytes written=288
HDFS: Number of read operations=16
HDFS: Number of large read operations=0
HDFS: Number of write operations=8
Job Counters
Launched map tasks=4
Other local map tasks=4
Total time spent by all maps in occupied slots (ms)=174096
Total time spent by all reduces in occupied slots (ms)=0
Map-Reduce Framework
Map input records=7
Map output records=7
Input split bytes=401
Spilled Records=0
Failed Shuffles=0
Merged Map outputs=0
GC time elapsed (ms)=205
CPU time spent (ms)=10510
Physical memory (bytes) snapshot=599060480
Virtual memory (bytes) snapshot=3535720448
Total committed heap usage (bytes)=335544320
File Input Format Counters
Bytes Read=0
File Output Format Counters
Bytes Written=288
15/01/17 20:28:54 INFO mapreduce.ImportJobBase: Transferred 288 bytes in 35.2792 seconds (8.1635 bytes/sec)
15/01/17 20:28:54 INFO mapreduce.ImportJobBase: Retrieved 7 records.四、查看导入HDFS上的数据
[hadoopUser@secondmgt ~]$ hadoop fs -cat /output/sqoop/* 56,hua,hanyun,男,开通,2013-12-02,0,1 58,feng,123456,男,开通,2013-11-22,0,0 59,test,123456,男,开通,2014-03-05,58,0 60,user1,123456,男,开通,2014-06-26,66,0 61,user2,123,男,开通,2013-12-13,56,0 62,user3,123456,男,开通,2013-12-14,0,0 64,kai.zhou,123456,?,??,2014-03-05,65,0
与原数据库中记录一样，导入成功。
五、选择部分数据导入
1、--columns参数指定列
Sqoop默认是将表中每条记录的所有属性值导入，有的时候，我们只需要导入部分属性值，这时可以使用--columns参数，指定需要导入的列名，多个列之间用逗号隔开。如下将users表中的用户名、性别和时间导入到HDFS中：
[hadoopUser@secondmgt ~]$ sqoop import --connect jdbc:mysql://secondmgt:3306/spice --username hive --password hive > --table users --columns "username,sex,datetime" --target-dir /output/sqoop/查看结果：
[hadoopUser@secondmgt ~]$ hadoop fs -cat /output/sqoop/* hua,男,2013-12-02 feng,男,2013-11-22 test,男,2014-03-05 user1,男,2014-06-26 user2,男,2013-12-13 user3,男,2013-12-14 kai.zhou,?,2014-03-052、--where参数过滤行
另一个参数--where，可以对行做过滤，得到部分符合条件的记录，而不是表中全部记录。如下，将users表中id值大于60的数据导入到HDFS中：
[hadoopUser@secondmgt conf]$ sqoop import --connect jdbc:mysql://secondmgt:3306/spice --username hive --password hive \ > --table users --where " id > 60" --target-dir /output/sqoop/查看结果：
[hadoopUser@secondmgt conf]$ hadoop fs -cat /output/sqoop/* 61,user2,123,男,开通,2013-12-13,56,0 62,user3,123456,男,开通,2013-12-14,0,0 64,kai.zhou,123456,?,??,2014-03-05,65,0
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原文地址：http://blog.csdn.net/niityzu/article/details/42834993
