问题导读：
1、--hive-import、--hive-overwrite的作用？
2、如何处理关系型数据库字段中字符串含有分隔符问题？
3、使用--hive-import默认字段分隔符是？一行记录分隔符是？
4、NULL值是怎么处理的？--null-string和--null-string的作用？
5、--hive-partition-key作用？分区值类型必须是？
6、--compression-codec作用？
7、Sqoop将关系型数据库数据导入Hive中，默认导入数据库是？默认导入路径是？如何指定某个特定的数据库？
一、原理及部分参数简介
1、Sqoop import主要功能是将数据导入到HDFS文件中。但是如果你有与Hadoop集群关联的Hive元数据服务，Sqoop也可以将数据导入到Hive中，通过创建表语句CREATE TABLE <表名>在Hive中定义数据布局。导入数据到Hive中很简单，在Sqoop命令行中，使用--hive-import选项。
2、 如果Hive中表已经存在，你可以使用--hive-overwrite选择来表明，在Hive中的此表必须被替换。如果你的数据已经被导入到HDFS中或者此步骤被忽略了，Sqoop将会产生一个Hive脚本，它包含"CREATE TABLE"操作使用Hive数据类型定义列和“LOAD DATA INPATH” 语句的来将数据文件加载到Hive warehouse目录中。
3、尽管Hive支持转义字符，但是它并不处理新行字符的转义。Hive使用Sqoop导入数据将会出现问题，当你的数据行中包含着含有Hive默认行分隔符(\n or \r)的字符串字段或者列分隔符(\01)。你可以使用--hive-drop-import-delims选项将那些字符删掉，提供给Hive兼容的文本数据，或者使用--hive-delims-replacement选择替换掉那些字符以用户自定义字符串以提供给Hive兼容的文本数据。这些选项仅仅在你使用Hive默认分隔符的时候使用。在已经指定不同分隔符的情况下，不应该使用。
如果你不使用指定的分隔符而使用--hive-import,那么默认使用^A作为字段分隔符， \n作为一条记录分隔符。
4、Sqoop默认的会将NULL值以string类型导入，在Hive中默认是使用\N表示NULL。这会导致，在Hive中执行查询的使用(like IS NULL)不起作用。你可以使用 --null-string和 --null-non-string在导入操作的时候。或者使用--input-null-string和--input-null-non-string在导出的时候来保护NULL值。因为Sqoop将会在生成的代码中使用这些参数。所以需要将\N变为\\N。如：$ sqoop import ... --null-string '\\N' --null-non-string '\\N'。
5、使用--hive-table 修改输出表名
6、Hive可以将数据分区导入以便提高查询性能。你可以使用--hive-partition-key或者 --hive-partition-value参数告诉Sqoop job以指定分区形式导入Hive中。分区值必须是个字符串。
7、使用--compression-codec 如后面接"com.hadoop.compression.lzo.LzopCodec"可以实现压缩。
二、启动Hive元数据服务
Hive安装此处不介绍，我使用的版本是Hive0.13.1，Hadoop2.2.0
[hadoopUser@secondmgt ~]$ hive --service metastore
Starting Hive Metastore Server
15/01/18 20:13:52 INFO Configuration.deprecation: mapred.reduce.tasks is deprecated. Instead, use mapreduce.job.reduces
15/01/18 20:13:52 INFO Configuration.deprecation: mapred.min.split.size is deprecated. Instead, use mapreduce.input.fileinputformat.split.minsize
15/01/18 20:13:52 INFO Configuration.deprecation: mapred.reduce.tasks.speculative.execution is deprecated. Instead, use mapreduce.reduce.speculative
15/01/18 20:13:52 INFO Configuration.deprecation: mapred.min.split.size.per.node is deprecated. Instead, use mapreduce.input.fileinputformat.split.minsize.per.node
15/01/18 20:13:52 INFO Configuration.deprecation: mapred.input.dir.recursive is deprecated. Instead, use mapreduce.input.fileinputformat.input.dir.recursive
15/01/18 20:13:52 INFO Configuration.deprecation: mapred.min.split.size.per.rack is deprecated. Instead, use mapreduce.input.fileinputformat.split.minsize.per.rack
15/01/18 20:13:52 INFO Configuration.deprecation: mapred.max.split.size is deprecated. Instead, use mapreduce.input.fileinputformat.split.maxsize
15/01/18 20:13:52 INFO Configuration.deprecation: mapred.committer.job.setup.cleanup.needed is deprecated. Instead, use mapreduce.job.committer.setup.cleanup.needed
三、原始数据库
查看原数据库表中内容
mysql> select * from users;四、执行基本导入操作
+----+-------------+----------+-----+-----------+------------+-------+------+
| id | username | password | sex | content | datetime | vm_id | isad |
+----+-------------+----------+-----+-----------+------------+-------+------+
| 56 | hua | sqoop | 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 |
| 65 | test1 | 111 | 男 | 未开通 | NULL | 0 | 0 |
| 66 | test2 | 111 | 男 | 未开通 | NULL | 0 | 0 |
| 67 | test3 | 113 | 男 | 未开通 | NULL | 0 | 0 |
| 68 | sqoopincr01 | 113 | 男 | 未开通 | NULL | 0 | 0 |
| 69 | sqoopincr02 | 113 | 男 | 未开通 | NULL | 0 | 0 |
| 70 | sqoopincr03 | 113 | 男 | 未开通 | NULL | 0 | 0 |
+----+-------------+----------+-----+-----------+------------+-------+------+
13 rows in set (0.00 sec)
[hadoopUser@secondmgt ~]$ sqoop import --hive-import --connect jdbc:mysql://secondmgt:3306/spice --username hive --password hive --table users --hive-table hiveusers上面是完整的执行过程，内部执行实际分三部，1.将数据导入hdfs（可在hdfs上找到相应目录），2.创建hive表名相同的表，3，将hdfs上数据传入hive表中 。如果不指定数据库，默认是导入到default数据库中，导入指定的数据库中的某个表中可以使用" 数据库名 . 表名"。默认存放路径是 warehouse/<表名>/目录下。
Warning: /usr/lib/hcatalog does not exist! HCatalog jobs will fail.
Please set $HCAT_HOME to the root of your HCatalog installation.
15/01/18 20:22:19 WARN tool.BaseSqoopTool: Setting your password on the command-line is insecure. Consider using -P instead.
15/01/18 20:22:19 INFO tool.BaseSqoopTool: Using Hive-specific delimiters for output. You can override
15/01/18 20:22:19 INFO tool.BaseSqoopTool: delimiters with --fields-terminated-by, etc.
15/01/18 20:22:19 WARN tool.BaseSqoopTool: It seems that you've specified at least one of following:
15/01/18 20:22:19 WARN tool.BaseSqoopTool: --hive-home
15/01/18 20:22:19 WARN tool.BaseSqoopTool: --hive-overwrite
15/01/18 20:22:19 WARN tool.BaseSqoopTool: --create-hive-table
15/01/18 20:22:19 WARN tool.BaseSqoopTool: --hive-table
15/01/18 20:22:19 WARN tool.BaseSqoopTool: --hive-partition-key
15/01/18 20:22:19 WARN tool.BaseSqoopTool: --hive-partition-value
15/01/18 20:22:19 WARN tool.BaseSqoopTool: --map-column-hive
15/01/18 20:22:19 WARN tool.BaseSqoopTool: Without specifying parameter --hive-import. Please note that
15/01/18 20:22:19 WARN tool.BaseSqoopTool: those arguments will not be used in this session. Either
15/01/18 20:22:19 WARN tool.BaseSqoopTool: specify --hive-import to apply them correctly or remove them
15/01/18 20:22:19 WARN tool.BaseSqoopTool: from command line to remove this warning.
15/01/18 20:22:19 INFO tool.BaseSqoopTool: Please note that --hive-home, --hive-partition-key,
15/01/18 20:22:19 INFO tool.BaseSqoopTool: hive-partition-value and --map-column-hive options are
15/01/18 20:22:19 INFO tool.BaseSqoopTool: are also valid for HCatalog imports and exports
15/01/18 20:22:19 INFO manager.MySQLManager: Preparing to use a MySQL streaming resultset.
15/01/18 20:22:19 INFO tool.CodeGenTool: Beginning code generation
15/01/18 20:22:19 INFO manager.SqlManager: Executing SQL statement: SELECT t.* FROM `users` AS t LIMIT 1
15/01/18 20:22:19 INFO manager.SqlManager: Executing SQL statement: SELECT t.* FROM `users` AS t LIMIT 1
15/01/18 20:22:19 INFO orm.CompilationManager: HADOOP_MAPRED_HOME is /home/hadoopUser/cloud/hadoop/programs/hadoop-2.2.0
Note: /tmp/sqoop-hadoopUser/compile/e5d129e2de5bcdea0f7e1db4beb24461/users.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
15/01/18 20:22:21 INFO orm.CompilationManager: Writing jar file: /tmp/sqoop-hadoopUser/compile/e5d129e2de5bcdea0f7e1db4beb24461/users.jar
15/01/18 20:22:21 WARN manager.MySQLManager: It looks like you are importing from mysql.
15/01/18 20:22:21 WARN manager.MySQLManager: This transfer can be faster! Use the --direct
15/01/18 20:22:21 WARN manager.MySQLManager: option to exercise a MySQL-specific fast path.
15/01/18 20:22:21 INFO manager.MySQLManager: Setting zero DATETIME behavior to convertToNull (mysql)
15/01/18 20:22:21 INFO mapreduce.ImportJobBase: Beginning import of users
15/01/18 20:22:21 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]
15/01/18 20:22:21 INFO Configuration.deprecation: mapred.jar is deprecated. Instead, use mapreduce.job.jar
15/01/18 20:22:21 INFO Configuration.deprecation: mapred.map.tasks is deprecated. Instead, use mapreduce.job.maps
15/01/18 20:22:22 INFO client.RMProxy: Connecting to ResourceManager at secondmgt/192.168.2.133:8032
15/01/18 20:22:23 INFO db.DataDrivenDBInputFormat: BoundingValsQuery: SELECT MIN(`id`), MAX(`id`) FROM `users`
15/01/18 20:22:23 INFO mapreduce.JobSubmitter: number of splits:4
15/01/18 20:22:23 INFO Configuration.deprecation: mapred.job.classpath.files is deprecated. Instead, use mapreduce.job.classpath.files
15/01/18 20:22:23 INFO Configuration.deprecation: user.name is deprecated. Instead, use mapreduce.job.user.name
15/01/18 20:22:23 INFO Configuration.deprecation: mapred.cache.files.filesizes is deprecated. Instead, use mapreduce.job.cache.files.filesizes
15/01/18 20:22:23 INFO Configuration.deprecation: mapred.cache.files is deprecated. Instead, use mapreduce.job.cache.files
15/01/18 20:22:23 INFO Configuration.deprecation: mapred.reduce.tasks is deprecated. Instead, use mapreduce.job.reduces
15/01/18 20:22:23 INFO Configuration.deprecation: mapred.output.value.class is deprecated. Instead, use mapreduce.job.output.value.class
15/01/18 20:22:23 INFO Configuration.deprecation: mapreduce.map.class is deprecated. Instead, use mapreduce.job.map.class
15/01/18 20:22:23 INFO Configuration.deprecation: mapred.job.name is deprecated. Instead, use mapreduce.job.name
15/01/18 20:22:23 INFO Configuration.deprecation: mapreduce.inputformat.class is deprecated. Instead, use mapreduce.job.inputformat.class
15/01/18 20:22:23 INFO Configuration.deprecation: mapred.output.dir is deprecated. Instead, use mapreduce.output.fileoutputformat.outputdir
15/01/18 20:22:23 INFO Configuration.deprecation: mapreduce.outputformat.class is deprecated. Instead, use mapreduce.job.outputformat.class
15/01/18 20:22:23 INFO Configuration.deprecation: mapred.cache.files.timestamps is deprecated. Instead, use mapreduce.job.cache.files.timestamps
15/01/18 20:22:23 INFO Configuration.deprecation: mapred.output.key.class is deprecated. Instead, use mapreduce.job.output.key.class
15/01/18 20:22:23 INFO Configuration.deprecation: mapred.working.dir is deprecated. Instead, use mapreduce.job.working.dir
15/01/18 20:22:23 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1421373857783_0022
15/01/18 20:22:23 INFO impl.YarnClientImpl: Submitted application application_1421373857783_0022 to ResourceManager at secondmgt/192.168.2.133:8032
15/01/18 20:22:23 INFO mapreduce.Job: The url to track the job: http://secondmgt:8088/proxy/application_1421373857783_0022/
15/01/18 20:22:23 INFO mapreduce.Job: Running job: job_1421373857783_0022
15/01/18 20:22:36 INFO mapreduce.Job: Job job_1421373857783_0022 running in uber mode : false
15/01/18 20:22:36 INFO mapreduce.Job: map 0% reduce 0%
15/01/18 20:22:46 INFO mapreduce.Job: map 25% reduce 0%
15/01/18 20:22:50 INFO mapreduce.Job: map 75% reduce 0%
15/01/18 20:22:56 INFO mapreduce.Job: map 100% reduce 0%
15/01/18 20:22:56 INFO mapreduce.Job: Job job_1421373857783_0022 completed successfully
15/01/18 20:22:57 INFO mapreduce.Job: Counters: 27
File System Counters
FILE: Number of bytes read=0
FILE: Number of bytes written=368076
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=521
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)=165592
Total time spent by all reduces in occupied slots (ms)=0
Map-Reduce Framework
Map input records=13
Map output records=13
Input split bytes=401
Spilled Records=0
Failed Shuffles=0
Merged Map outputs=0
GC time elapsed (ms)=192
CPU time spent (ms)=10500
Physical memory (bytes) snapshot=588156928
Virtual memory (bytes) snapshot=3525619712
Total committed heap usage (bytes)=337641472
File Input Format Counters
Bytes Read=0
File Output Format Counters
Bytes Written=521
15/01/18 20:22:57 INFO mapreduce.ImportJobBase: Transferred 521 bytes in 35.2437 seconds (14.7828 bytes/sec)
15/01/18 20:22:57 INFO mapreduce.ImportJobBase: Retrieved 13 records.
15/01/18 20:22:57 INFO manager.SqlManager: Executing SQL statement: SELECT t.* FROM `users` AS t LIMIT 1
15/01/18 20:22:57 WARN hive.TableDefWriter: Column datetime had to be cast to a less precise type in Hive
15/01/18 20:22:57 INFO hive.HiveImport: Loading uploaded data into Hive
15/01/18 20:23:03 INFO hive.HiveImport: 15/01/18 20:23:03 INFO Configuration.deprecation: mapred.reduce.tasks is deprecated. Instead, use mapreduce.job.reduces
15/01/18 20:23:03 INFO hive.HiveImport: 15/01/18 20:23:03 INFO Configuration.deprecation: mapred.min.split.size is deprecated. Instead, use mapreduce.input.fileinputformat.split.minsize
15/01/18 20:23:03 INFO hive.HiveImport: 15/01/18 20:23:03 INFO Configuration.deprecation: mapred.reduce.tasks.speculative.execution is deprecated. Instead, use mapreduce.reduce.speculative
15/01/18 20:23:03 INFO hive.HiveImport: 15/01/18 20:23:03 INFO Configuration.deprecation: mapred.min.split.size.per.node is deprecated. Instead, use mapreduce.input.fileinputformat.split.minsize.per.node
15/01/18 20:23:03 INFO hive.HiveImport: 15/01/18 20:23:03 INFO Configuration.deprecation: mapred.input.dir.recursive is deprecated. Instead, use mapreduce.input.fileinputformat.input.dir.recursive
15/01/18 20:23:03 INFO hive.HiveImport: 15/01/18 20:23:03 INFO Configuration.deprecation: mapred.min.split.size.per.rack is deprecated. Instead, use mapreduce.input.fileinputformat.split.minsize.per.rack
15/01/18 20:23:03 INFO hive.HiveImport: 15/01/18 20:23:03 INFO Configuration.deprecation: mapred.max.split.size is deprecated. Instead, use mapreduce.input.fileinputformat.split.maxsize
15/01/18 20:23:03 INFO hive.HiveImport: 15/01/18 20:23:03 INFO Configuration.deprecation: mapred.committer.job.setup.cleanup.needed is deprecated. Instead, use mapreduce.job.committer.setup.cleanup.needed
15/01/18 20:23:03 INFO hive.HiveImport:
15/01/18 20:23:03 INFO hive.HiveImport: Logging initialized using configuration in file:/home/hadoopUser/cloud/hive/apache-hive-0.13.1-bin/conf/hive-log4j.properties
15/01/18 20:23:03 INFO hive.HiveImport: SLF4J: Class path contains multiple SLF4J bindings.
15/01/18 20:23:03 INFO hive.HiveImport: 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]
15/01/18 20:23:03 INFO hive.HiveImport: 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]
15/01/18 20:23:03 INFO hive.HiveImport: SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
15/01/18 20:23:03 INFO hive.HiveImport: SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
15/01/18 20:23:06 INFO hive.HiveImport: OK
15/01/18 20:23:06 INFO hive.HiveImport: Time taken: 1.542 seconds
15/01/18 20:23:06 INFO hive.HiveImport: Loading data to table default.hiveusers
15/01/18 20:23:06 INFO hive.HiveImport: Table default.hiveusers stats: [numFiles=5, numRows=0, totalSize=521, rawDataSize=0]
15/01/18 20:23:06 INFO hive.HiveImport: OK
15/01/18 20:23:06 INFO hive.HiveImport: Time taken: 0.668 seconds
15/01/18 20:23:06 INFO hive.HiveImport: Hive import complete.
15/01/18 20:23:06 INFO hive.HiveImport: Export directory is empty, removing it.
查看结果：
hive> select * from hiveusers;
OK
56 hua sqoop 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
65 test1 111 男 未开通 null 0 0
66 test2 111 男 未开通 null 0 0
67 test3 113 男 未开通 null 0 0
68 sqoopincr01 113 男 未开通 null 0 0
69 sqoopincr02 113 男 未开通 null 0 0
70 sqoopincr03 113 男 未开通 null 0 0
Time taken: 0.46 seconds, Fetched: 13 row(s)
desc describe
hive> desc hiveusers;
OK
id int
username string
password string
sex string
content string
datetime string
vm_id int
isad int
Time taken: 0.133 seconds, Fetched: 8 row(s)
由上面查询结果可知NULL被当做字符串处理了，以null被导入进Hive表中
五、对NULL值进行处理[hadoopUser@secondmgt ~]$ sqoop import --connect jdbc:mysql://secondmgt:3306/spice --username hive --password hive --table users --hive-table test.hiveusers --hive-import --hive-overwrite --null-string '\\N' --null-non-string '\\N'再次查看结果：
hive> select * from hiveusers;NULL值已正确处理
OK
56 hua sqoop 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
65 test1 111 男 未开通 NULL 0 0
66 test2 111 男 未开通 NULL 0 0
67 test3 113 男 未开通 NULL 0 0
68 sqoopincr01 113 男 未开通 NULL 0 0
69 sqoopincr02 113 男 未开通 NULL 0 0
70 sqoopincr03 113 男 未开通 NULL 0 0
Time taken: 0.064 seconds, Fetched: 13 row(s)
六、完整例子
附上一个完整例子，压缩没验证，有兴趣的可以验证下是否正确，可与我交流一下：
[hadoopUser@secondmgt ~]$ sqoop import --connect jdbc:mysql://secondmgt:3306/spice --username hive --password hive --table users --hive-table test.hiveusers --hive-import --hive-overwrite --null-string '\\N' --null-non-string '\\N' --input-fields-terminated-by '\t' --input-lines-terminated-by '\n' --compression-codec "com.hadoop.compression.lzo.LzopCodec"
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