Comparing sql and nosql dbs

The following is a short, incomplete history of the SQL
 1987 – Initial ISO/IEC Standard
 1989 – Referential Integrity
 1992 – SQL2
 1995 SQL/CLI (ODBC)
 1996 SQL/PSM – Procedural Language extensions
 1999 – User Defined Types
 2003 – SQL/XML
 2008 – Expansions and corrections
 2011 (or 2012) System Versioned and Application Time
Period Tables
2

 Data stored in columns and tables
 Relationships represented by data
 Data Manipulation Language
 Data Definition Language
 Transactions
 Abstraction from physical layer
3

 Applications specify what, not how
 Query optimization engine
 Physical layer can change without modifying
applications
 Create indexes to support queries
 In Memory databases
4

 Data manipulated with Select, Insert, Update, &
Delete statements
 Select T1.Column1, T2.Column2 …
From Table1, Table2 …
Where T1.Column1 = T2.Column1 …
 Data Aggregation
 Compound statements
 Functions and Procedures
 Explicit transaction control
5

 Schema defined at the start
 Create Table (Column1 Datatype1, Column2 Datatype
2, …)
 Constraints to define and enforce relationships
 Primary Key
 Foreign Key
 Etc.
 Triggers to respond to Insert, Update , & Delete
 Stored Modules
 Alter …
 Drop …
 Security and Access Control
6

 Atomic – All of the work in a transaction completes
(commit) or none of it completes
 Consistent – A transaction transforms the database
from one consistent state to another consistent state.
Consistency is defined in terms of constraints.
 Isolated – The results of any changes made during a
transaction are not visible until the transaction has
committed.
 Durable – The results of a committed transaction
survive failures
7

 Commercial
 IBM DB2
 Oracle RDMS
 Microsoft SQL Server
 Sybase SQL Anywhere
 Open Source (with commercial options)
 MySQL
 Ingres
Significant portions of the
world’s economy use SQL databases!
8

From www.nosql-database.org:
Next Generation Databases mostly addressing some of the
points: being non-relational, distributed, open-source
and horizontal scalable. The original intention has been
modern web-scale databases. The movement began
early 2009 and is growing rapidly. Often more
characteristics apply as: schema-free, easy replication
support, simple API, eventually consistent / BASE
(not ACID), a huge data amount, and more.
9

http://www.nosql-database.org/ lists 122 NoSQL
Databases
 Cassandra
 CouchDB
 Hadoop & Hbase
 MongoDB
 StupidDB
 Etc.
10

 Large data volumes
 Google’s “big data”
 Scalable replication and distribution
 Potentially thousands of machines
 Potentially distributed around the world
 Queries need to return answers quickly
 Mostly query, few updates
 Asynchronous Inserts & Updates
 Schema-less
 ACID transaction properties are not needed – BASE
 CAP Theorem
 Open source development
11

 Acronym contrived to be the opposite of ACID
 Basically Available,
 Soft state,
 Eventually Consistent
 Characteristics
 Weak consistency – stale data OK
 Availability first
 Best effort
 Approximate answers OK
 Aggressive (optimistic)
 Simpler and faster
12

A distributed system can support only two of the
following characteristics:
 Consistency
 Availability
 Partition tolerance
The slides from Brewer’s July 2000 talk do not define
these characteristics.
13

 all nodes see the same data at the same time –
Wikipedia
 client perceives that a set of operations has occurred
all at once – Pritchett
 More like Atomic in ACID transaction properties
14

 node failures do not prevent survivors from
continuing to operate – Wikipedia
 Every operation must terminate in an intended
response – Pritchett
15

 the system continues to operate despite
arbitrary message loss – Wikipedia
 Operations will complete, even if individual
components are unavailable – Pritchett
16

Discussing NoSQL databases is complicated because
there are a variety of types:
 Column Store – Each storage block contains data from
only one column
 Document Store – stores documents made up of
tagged elements
 Key-Value Store – Hash table of keys
17

 XML Databases
 Graph Databases
 Codasyl Databases
 Object Oriented Databases
 Etc…
 Will not address these today
18

 Each storage block contains data from only one
column
 Example: Hadoop/Hbase
 http://hadoop.apache.org/
 Yahoo, Facebook
 Example: Ingres VectorWise
 Column Store integrated with an SQL database
 http://www.ingres.com/products/vectorwise
19

 More efficient than row (or document) store if:
 Multiple row/record/documents are inserted at the
same time so updates of column blocks can be
aggregated
 Retrievals access only some of the columns in a
row/record/document
20

 Example: CouchDB
 http://couchdb.apache.org/
 BBC
 Example: MongoDB
 http://www.mongodb.org/
 Foursquare, Shutterfly
 JSON – JavaScript Object Notation
21

{
"_id": "guid goes here",
"_rev": "314159",
"type": "abstract",
"author": "Keith W. Hare"
"title": "SQL Standard and NoSQL Databases",
"body": "NoSQL databases (either no-SQL or Not Only SQL)
are currently a hot topic in some parts of
computing.",
"creation_timestamp": "2011/05/10 13:30:00 +0004"
}
22

 "_id"
 GUID – Global Unique Identifier
 Passed in or generated by CouchDB
 "_rev"
 Revision number
 Versioning mechanism
 "type", "author", "title", etc.
 Arbitrary tags
 Schema-less
 Could be validated after the fact by user-written routine
23

 Hash tables of Keys
 Values stored with Keys
 Fast access to small data values
 Example – Project-Voldemort
 http://www.project-voldemort.com/
 Linkedin
 Example – MemCacheDB
 http://memcachedb.org/
 Backend storage is Berkeley-DB
24

 Technique for indexing and searching large data
volumes
 Two Phases, Map and Reduce
 Map
 Extract sets of Key-Value pairs from underlying data
 Potentially in Parallel on multiple machines
 Reduce
 Merge and sort sets of Key-Value pairs
 Results may be useful for other searches
25

 Map Reduce techniques differ across products
 Implemented by application developers, not by
underlying software
26

Google granted US Patent 7,650,331, January 2010
System and method for efficient large-scale data processing
A large-scale data processing system and method includes one
or more application-independent map modules configured to
read input data and to apply at least one application-specific
map operation to the input data to produce intermediate data
values, wherein the map operation is automatically parallelized
across multiple processors in the parallel processing
environment. A plurality of intermediate data structures are
used to store the intermediate data values. One or more
application-independent reduce modules are configured to
retrieve the intermediate data values and to apply at least one
application-specific reduce operation to the intermediate
data values to provide output data.
27

 Syntax varies
 HTML
 Java Script
 Etc.
 Asynchronous – Inserts and updates do not wait for
confirmation
 Versioned
 Optimistic Concurrency
28

 Syntax Varies
 No set-based query language
 Procedural program languages such as Java, C, etc.
 Application specifies retrieval path
 No query optimizer
 Quick answer is important
 May not be a single “right” answer
29

 Small upfront software costs
 Suitable for large scale distribution on commodity
hardware
30

 NoSQL databases reject:
 Overhead of ACID transactions
 “Complexity” of SQL
 Burden of up-front schema design
 Declarative query expression
 Yesterday’s technology
 Programmer responsible for
 Step-by-step procedural language
 Navigating access path
31

 SQL Databases
 Predefined Schema
 Standard definition and interface language
 Tight consistency
 Well defined semantics
 NoSQL Database
 No predefined Schema
 Per-product definition and interface language
 Getting an answer quickly is more important than
getting a correct answer
32

Comparing sql and nosql dbs

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