Hive
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. EMP and DEPT tables are pretty popular between Oracle users. These tables were very handy in quickly trying new queries. Also, there exists a DUAL table in Oracle that was pretty useful in evaluate expressions, like- “Select (SYSDATE + 1/24) as OneHourFromNow FROM DUAL“. These tables doesn’t exists in Hive, but we can create
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. There are few type of UDFs that we can write in Hive. Functions that act on each column value passed to it, e.g. Select Length(name) From Customer Specific functions written for a specific data type (simple UDFs) Generic functions written to working with more than one data type Functions that act on a group
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. HCatalog is an extension of Hive and in a nutshell, it exposes the schema information in Hive Metastore such that applications outside of Hive can use it. The objective of HCatalog is to hold the following type of information about the data in HDFS – Location of the data Metadata about the data (e.g.
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. There are a few type of UDFs that we can write in Hive. Functions that act on each column value passed to it, e.g. Select Length(name) From Customer Specific functions written for a specific data type Generic functions written to working with more than one data type (GenericUDF) Functions that act on a group
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. Apache Hive is an abstraction on top of HDFS data, that allow querying the data using the familiar SQL like language, called HiveQL (Hive Query Language). Hive was developed at Facebook to allow data analysts to query data using an SQL like language. Hive has limited commands and is similar to basic SQL (advance SQL options
Vipul Pathak 