What is the difference between a Relational and Non-Relational Database

Question

I know that solutions like MySQL  PostgreSQL and MS SQL Server are relational database systems  and NoSQL  MongoDB  etc  are Non-Relational DBMS   However  what are the differences between the two types of system    Layman terms are preferable   Thanks

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Hmm  not quite sure what your question is   In the title you ask about Databases  DB   whereas in the body of your text you ask about Database Management Systems  DBMS   The two are completely different and require different answers   A DBMS is a tool that allows you to access a DB   Other than the data itself  a DB is the concept of how that data is structured   So just like you can program with Oriented Object methodology with a non-OO powered compiler  or vice-versa  so can you set-up a relational database without an RDBMS or use an RDBMS to store non-relational data   I ll focus on what Relational Database  RDB  means and leave the discussion about what systems do to others   A relational database  the concept  is a data structure that allows you to link information from different  tables   or different types of data buckets  A data bucket must contain what is called a key or index  that allows to uniquely identify any atomic chunk of data within the bucket   Other data buckets may refer to that key so as to create a link between their data atoms and the atom pointed to by the key   A non-relational database just stores data without explicit and structured mechanisms to link data from different buckets to one another   As to implementing such a scheme  if you have a paper file with an index and in a different paper file you refer to the index to get at the relevant information  then you have implemented a relational database  albeit quite a simple one  So you see that you do not even need a computer  of course it can become tedious very quickly without one to help   similarly you do not need an RDBMS  though arguably an RDBMS is the right tool for the job  That said there are variations as to what the different tools out there can do so choosing the right tool for the job may not be all that straightforward   I hope this is layman terms enough and is helpful to your understanding

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Try to explain this question in a level referring to a little bit technology  Take MongoDB and Traditional SQL for comparison  imagine the scenario of  posting a Tweet on Twitter  This tweet contains 9 pictures  How do you store this tweet and its corresponding pictures   In terms of traditional relationship SQL  you can store the tweets and pictures in separate tables  and represent the connection through building a new table   What s more  you can set a field which is an image type  and zip the 9 pictures into a binary document and store it in this field   Using MongoDB  you could build a document like this  similar to the concept of a table in relational SQL        id   XXX     user   XXX     date   xxxx-xx-xx     content      text   XXXX     picture    p1 png   p2 png   p3 png        Therefore  in my opinion  the main difference is about how do you store the data and the storage level of the relationships between them   In this example  the data is the tweet and the pictures  The different mechanism about storage level of relationship between them also play a important role in the difference between both   I hope this small example helps show the difference between SQL and NoSQL  ACID and BASE    Here s a link of picture about the goals of NoSQL from the Internet   http   icamchuwordpress-wordpress stor sinaapp com uploads 2015 01 dbc795f6f262e9d01fa0ab9b323b2dd1 b png

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First up let me start by saying why we need a database   We need a database to help organise information in such a manner that we can retrieve that data stored in a efficient manner   Examples of relational database management systems SQL    1 Oracle Database    2 SQLite    3 PostgreSQL    4 MySQL     5 Microsoft SQL Server     6 IBM DB2  Examples of non relational database management systems NoSQL   1 MongoDB  2 Cassandra  3 Redis  4 Couchbase  5 HBase  6 DocumentDB  7 Neo4j  Relational databases have normalized data  as in information is stored in tables in forms of rows and columns  and normally when data is in normalized form  it helps to reduce data redundancy  and the data in tables are normally related to each other  so when we want to retrieve the data  we can query the data by using join statements and retrieve data as per our need This is suited when we want to have more writes  less reads  and not much data involved  also its really easy relatively to update data in tables than in non relational databases  Horizontal scaling not possible  vertical scaling possible to some extent CAP Consistency  Availability  Partition Tolerant   and ACID  Atomicity  Consistency  Isolation  Duration compliance   Let me show entering data to a relational database using PostgreSQL as an example    First create a product table as follows   CREATE TABLE products       product no integer      name text      price numeric      then insert the data  INSERT INTO products  product no  name  price  VALUES  1   Cheese   9 99     Let s look at another different example    Here in a relational database  we can link the student table and subject table using relationships  via foreign key  subject ID  but in a non relational database no need to have two documents  as no relationships  so we store all the subject details and student details in one document say student document  then data is getting duplicated  which makes updating records troublesome   In non relational databases  there is no fixed schema  data is not normalized  no relationships between data is created  all data mostly put in one document  Well suited when handling lots of data  and can transfer lots of data at once  best where high amounts of reads and less writes  and less updates  bit difficult to query data  as no fixed schema  Horizontal and vertical scaling is possible CAP  Consistency  Availability  Partition Tolerant and BASE  Basically Available  soft state  Eventually consistent compliance   Let me show an example to enter data to a non relational database using Mongodb  db users insertOne  name     Mary     age  28   occupation     writer       db users insertOne  name     Ben      age  21     Hence you can understand that to the database called db  and there is a collections called users  and document called insertOne to which we add data  and there is no fixed schema as our first record has 3 attributes  and second attribute has 2 attributes only  this is no problem in non relational databases  but this cannot be done in relational databases  as relational databases have a fixed schema   Let s look at another different example    Studname     Ash     Subname     Mathematics     LecturerName     Mr  Oak        Hence we can see in non relational database we can enter both student details and subject details into one document  as no relationships defined in non relational databases  but here this way can lead to data duplication  and hence errors in updating can occur therefore   Hope this explains everything

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In layman terms it s strongly structured vs unstructured  which implies that you have different degrees of adaptability for your DB  Differences arise in indexation particularly as you need to ensure that a certain reference index can link to a another item -  this a relation  The more strict structure of relational DB comes from this requirement   To note that NosDB apaprently provides both relational and non relational DBs and a way to query both http   www alachisoft com nosdb sql-cheat-sheet html

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Most of what you  know  is wrong   First of all  as a few of the relational gurus routinely  and sometimes stridently  point out  SQL doesn t really fit nearly as closely with relational theory as many people think  Second  most of the differences in  NoSQL  stuff has relatively little to do with whether it s relational or not  Finally  it s pretty difficult to say how  NoSQL  differs from SQL because both represent a pretty wide range of possibilities   The one major difference that you can count on is that almost anything that supports SQL supports things like triggers in the database itself -- i e  you can design rules into the database proper that are intended to ensure that the data is always internally consistent  For example  you can set things up so your database asserts that a person must have an address  If you do so  anytime you add a person  it will basically force you to associate that person with some address  You might add a new address or you might associate them with some existing address  but one way or another  the person must have an address  Likewise  if you delete an address  it ll force you to either remove all the people currently at that address  or associate each with some other address  You can do the same for other relationships  such as saying every person must have a mother  every office must have a phone number  etc   Note that these sorts of things are also guaranteed to happen atomically  so if somebody else looks at the database as you re adding the person  they ll either not see the person at all  or else they ll see the person with the address  or the mother  etc    Most of the NoSQL databases do not attempt to provide this kind of enforcement in the database proper  It s up to you  in the code that uses the database  to enforce any relationships necessary for your data  In most cases  it s also possible to see data that s only partially correct  so even if you have a family tree where every person is supposed to be associated with parents  there can be times that whatever constraints you ve imposed won t really be enforced  Some will let you do that at will  Others guarantee that it only happens temporarily  though exactly how long it can will last can be open to question

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The difference between relational and non-relational is exactly that   The relational database architecture provides with constraints objects such as primary keys  foreign keys  etc that allows one to tie two or more tables in a relation   This is good so that we normalize our tables which is to say split information about what the database represents into many different tables  once can keep the integrity of the data   For example  say you have a series of table that houses information about an employee   You could not delete a record from a table without deleting all the records that pertain to such record from the other tables   In this way you implement data integrity   The non-relational database doesn t provide this constraints constructs that will allow you to implement data integrity   Unless you don t implement this constraint in the front end application that is utilized to populate the databases  tables  you are implementing a mess that can be compared with the wild west

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The relational database uses a formal system of predicates to address data  The underlying physical implementation is of no substance and can vary to optimize for certain operations  but it must always assume the relational model  In layman s terms  that s just saying I know exactly how many values  attributes  each row  tuple  in my table  relation  has and now I want to exploit the fact accordingly  thoroughly and to it s extreme  That s the true nature of the beast  nbsp   Since we re obviously the generation that has had a relational upbringing  if you look at NoSQL database models from the perspective of the relational model  again in layman s terms  the first obvious difference is that no assumptions about the number of values a row can contain is ever made  This is really oversimplifying the matter and does not cleanly apply to the intricacies of the physical models of every NoSQL database  but it s the pinnacle of the relational model and the first assumption we have to leave behind or  if you d rather  the biggest leap we have to make   We can agree to two things that are true for every DBMS  it can store any kind of data and has enough mathematical underpinnings to make it possible to manage the data in any way imaginable  The reality is that you ll never want to make the mistake of putting any of the two points to the test  but rather just stick with what the actual DBMS was really made for  In layman s terms  respect the beast within    Please note that I ve avoided comparing the  obviously  well founded standards revolving around the relational model against the many flavors provided by NoSQL databases  If you d like  consider NoSQL databases as an umbrella term for any DBMS that does not completely assume the relational model  in exclusion to everything else  The differences are too many  but that s the principal difference and the one I think would be of most use to you to understand the two

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Relational databases have a mathematical basis  set theory  relational theory   which are distilled into SQL    Structured Query Language   NoSQL s many forms  e g  document-based  graph-based  object-based  key-value store  etc   may or may not be based on a single underpinning mathematical theory   As S  Lott has correctly pointed out  hierarchical data stores do indeed have a mathematical basis   The same might be said for graph databases     I m not aware of a universal query language for NoSQL databases

[relational-database] What is the difference between a Relational and Non-Relational Database?

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