Hive 外部表与内部表命令 [英] Hive External Table vs Internal table commands

问题描述

假设我有这两个表:

外部:

create external table emp_feedback (
  emp_id int,
  emp_name string
)
LOCATION '/user/hive/warehouse/mydb.db/contacts';

内部:

create table emp_feedback (
  emp_id int,
  emp_name string
)
LOAD DATA INPATH 'file_location_of_csv' INTO TABLE emp_feedback;

1. 当我说:LOCATION '/user/hive/warehouse/mydb.db/contacts'; 对于外部表是否意味着该表的数据可以在目录 '/user/hive/warehouse/mydb.db/contacts';?所以该目录必须事先存在于 HDFS 中?
2. 我可以将 LOAD DATA INPATH... 用于 external 表还是仅用于 internal 表.反之亦然，我可以将 Location... 用于内部表吗?

1. When I say: LOCATION '/user/hive/warehouse/mydb.db/contacts'; for the external table does that mean that the data for that table is found in the directory '/user/hive/warehouse/mydb.db/contacts';? So that directory has to exist in HDFS before hand?
2. Can I use LOAD DATA INPATH... for an external table or is that only used for internal tables. And vice versa can I use Location... for an internal table?

推荐答案

1. (a) 是的.你是对的，这意味着数据是在那个位置/目录中找到的

2. (b) 否.目录不必存在来创建架构，如果目录不存在，Hive 将创建该目录.但是这样做没有意义，因为您的表将是空的，因此您的查询将是空的.但将来，您可以将数据移动到该位置并使用该表.

1. (a) Yes. You are right, it means that the data is found in that location/directory

2. (b) No. The directory doesn't have to exist to create a Schema, Hive will create the directory if it doesn't exist. But there is no point in doing as your table will be empty therefore your query will be empty. But in the future, you can move data to that location and use that table.

(a) LOAD DATA INPATH 可用于外部和内部表.当您这样做时，它会将数据移动到架构指定的位置(对于外部表)或 /.../warehouse/...(对于内部表)

(a) LOAD DATA INPATH can be used for both external and internal tables. When you do, it moves the data, to the location specified by the schema (for external tables) or to /.../warehouse/... (for internal tables)

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