Hive(ppt)

What is Hive?
Hive is a data warehouse infrastructure tool to
process structure data in Hadoop. It resides on top of
Hadoop to summarize Big Data, and makes querying
and analyzing easy.
Initially Hive was developed by Facebook, later the
Apache Software Foundation took it up and
developed it further as an open source under the name
Apache Hive.

Features of Hive
It stores Schema in a database and processed data
into HDFS(Hadoop Distributed File System).
It is designed for OLAP.
It provides SQL type language for querying called
HiveQL or HQL.
It is familiar, fast, scalable, and extensible.

Architecture of Hive
User Interface - Hive is a data warehouse infrastructure software that can
create interaction between user and HDFS. The user interfaces that Hive
supports are Hive Web UI, Hive command line, and Hive HD.
Meta Store -Hive chooses respective database servers to store the schema
or Metadata of tables, databases, columns in a table, their data types and
HDFS mapping.
HiveQL Process Engine- HiveQL is similar to SQL for querying on
schema info on the Megastore. It is one of the replacements of traditional
approach for MapReduce program. Instead of writing MapReduce program in
Java, we can write a query for MapReduce job and process it.

Execution Engine - The conjunction part of
HiveQL process Engine and MapReduce is
Hive Execution Engine. Execution engine
processes the query and generates results as
same as MapReduce results. It uses the flavor
of MapReduce.
HDFS or HBASE - Hadoop distributed
file system or HBASE are the data storage
techniques to store data into the file system.

Working of Hive
Execute Query- The Hive interface such as Command Line or
Web UI sends query Driver to execute.
Get Plan- The driver takes the help of query complier that parses
the query to check the syntax and query plan or the requirement of
query.
Get Metadata- The compiler sends metadata request to Megastore
Send Metadata- Metastore sends metadata as a response to the
compiler.

Send Plan- The compiler checks the requirement and
resends the plan to the driver. Up to here, the parsing
and compiling of a query is complete.
Execute Plan- the driver sends the execute plan to the
execution engine.
Execute Job- Internally, the process of execution job is
a MapReduce job. The execution engine sends the job
to JobTracker, which is in Name node and it assigns
this job to TaskTracker, which is in Data node. Here,
the query executes MapReduce job.

Metadata Ops- Meanwhile in execution, the
execution engine can execute metadata operations
with Metastore.
Fetch Result- The execution engine receives the
results from Data nodes.
Send Results- The execution engine sends those
resultant values to the driver.
Send Results- The driver sends the results to Hive
Interfaces.

Hive- Data Types
All the data types in hive are classified into four
types
Column Types
Literals
Null Values
Complex Types

Column Types
Integral Types - Integer type data can be specified using
integral data types, INT. When the data range exceeds the
range of INT, you need to use BIGINT and if the data
range is smaller than the INT, you use SMALLINT.
TINYINT is smaller than SMALLINT.
String Types - String type data types can be specified using
single quotes (' ') or double quotes (" "). It contains two data
types: VARCHAR and CHAR. Hive follows C-types
escape characters.

Timestamp - It supports traditional UNIX timestamp with optional
nanosecond precision. It supports java.sql.Timestamp format
“YYYY-MM-DD HH:MM:SS.fffffffff” and format “yyyy-mm-
dd hh:mm:ss.ffffffffff”.
Dates - DATE values are described in year/month/day format
in the form {{YYYY-MM-DD}}.
Decimals -The DECIMAL type in Hive is as same as Big
Decimal format of Java. It is used for representing immutable
arbitrary precision.
Union Types - Union is a collection of heterogeneous data types.
You can create an instance using create union.

Literals
Floating Point Types - Floating point types are
nothing but numbers with decimal points. Generally,
this type of data is composed of DOUBLE data
type.
Decimal Type - Decimal type data is nothing but
floating point value with higher range than
DOUBLE data type. The range of decimal type is
approximately -10-308
to 10308
.

Complex Types
Arrays - Arrays in Hive are used the same way they are used in Java.
Syntax: ARRAY<data_type>
Maps - Maps in Hive are similar to Java Maps.
Syntax: MAP<primitive_type, data_type>
Structs - Structs in Hive is similar to using complex data with comment.
Syntax: STRUCT<col_name : data_type [ COMMENT
col_comment, … ]>

Create Database
hive> CREATE DATABASE [IF
NOT EXISTS] userdb;
hive> CREATE SCHEMA userdb;
hive> SHOW DATABASES;

Drop Database
hive>DROP DATABASE [IF
EXISTS] userdb;
hive> DROP DATABASE [IF
EXISTS] userdb CASCADE;
hive> DROP SCHEMA userdb;

Create Table
hive> CREATE TABLE IF NOT EXISTS
employee(eid int, name String, salary String, destination
String)
>COMMENT ‘Employee details’
>ROW FORMAT DELIMITED
>FIELDS TERMINATED BY ‘t’
>LINES TERMINATED BY ‘n’
>STORED AS TEXTFILE;

Partition
Hive organizes tables into partitions. It is a way of dividing a
table into related parts based on the values of partitioned
columns such as date, city, and department. Using partition, it
is easy to query a portion of the data.
Adding partition- Syntax - hive> ALTER TABLE
employee ADD PARTITION(year =‘2013’) location
‘/2012/part2012’;
Dropping partition - Syntax - hive>ALTER TABLE
employee DROP [IF EXISTS] PARTITION
(year=‘2013’);

id, name, dept, year
1, Mark, TP, 2012
2, Bob, HR, 2012
3, Sam,SC, 2013
4, Adam, SC, 2013

HiveQL - Select Where
The Hive Query Language (HiveQL) is a
query language for Hive to process and analyze
structured data in a Metastore.
hive> SELECT * FROM employee
WHERE salary>30000;

HiveQL - Select Order
By
The ORDER BY clause is used to retrieve
the details based on one column and sort the
result set by ascending or descending order.
hive> SELECT Id, Name, Dept FROM
employee ORDER BY DEPT;

HiveQL - Select-Group
By
The GROUP BY clause is used to group all
the records in a result set using a particular
collection column. It is used to query a group of
records.
hive> SELECT Dept,count(*) FROM
employee GROUP BY DEPT;

HiveQL - Select-Joins
JOIN is a clause that is used for combining specific fields from two tables by
using values common to each one. It is used to combine records from two or
more tables in the database. It is more or less similar to SQL JOIN.
There are different types of joins given as follows:
•
JOIN
•
LEFT OUTER JOIN
•
RIGHT OUTER JOIN
•
FULL OUTER JOIN

JOIN
JOIN clause is used to combine and retrieve the
records from multiple tables. JOIN is same as
OUTER JOIN in SQL. A JOIN condition is to
be raised using the primary keys and foreign keys of
the tables.
hive> SELECT c.ID, c.NAME, c.AGE,
o.AMOUNT FROM CUSTOMERS c
JOIN ORDERS o ON (c.ID =
o.CUSTOMER_ID);

Left Outer Join
The HiveQL LEFT OUTER JOIN returns all the rows
from the left table, even if there are no matches in the right
table. This means, if the ON clause matches 0 (zero) records
in the right table, the JOIN still returns a row in the result, but
with NULL in each column from the right table.
hive> SELECT c.ID, c.NAME, o.AMOUNT,
o.DATE FROM CUSTOMERS c LEFT
OUTER JOIN ORDERS o ON (c.ID =
o.CUSTOMER_ID);

Right Outer Join
The HiveQL RIGHT OUTER JOIN returns all
the rows from the right table, even if there are no matches
in the left table. If the ON clause matches 0 (zero)
records in the left table, the JOIN still returns a row in
the result, but with NULL in each column from the left
table.
o.DATE FROM CUSTOMERS c RIGHT
o.CUSTOMER_ID);

Full Outer Join
The HiveQL FULL OUTER JOIN combines the
records of both the left and the right outer tables that
fulfill the JOIN condition. The joined table contains
either all the records from both the tables, or fills in
NULL values for missing matches on either side.
o.DATE FROM CUSTOMERS c FULL
o.CUSTOMER_ID);

Hive(ppt)

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