# SQL vs NoSQL databases

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**What's the difference?** :cold_sweat:

* SQL databases are relational (defines relationships in the form of tables.)

* noSQL databases are non-relational/distributed (do not require a fixed schema, avoids joins)

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**SQL** databases use structured query language (SQL) for defining and manipulating data & are table-based. SQL requires that you use predefined schemas to determine the structure of your data before you work with it. In addition, all of your data must follow the same structure. :nail_care:

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**noSQL** database, on the other hand, has dynamic schema for unstructured data, and data is stored in many ways: it can be column-oriented, document-oriented, graph-based or organized as a KeyValue store. Does not require a particular query language. :frowning:

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**Examples**

**SQL** --> Oracle, Postgres, and MS-SQL

**noSQL** --> MongoDB, Redis, Neo4j, Cassandra, Hbase

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## Examples of the data structure of SQL and NoSQL databases

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### SQL

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1. Relational database in tabular format (rows and columns)

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2. Online analytical processing, or OLAP uses multidimensional data 

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### NoSQL

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1. A column family containing 3 rows. Each row contains its own set of columns.

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2. A graph database is essentially a collection of nodes and edges. Each node represents an entity (such as a person or business) and each edge represents a connection or relationship between two nodes.

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3. Document database

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4. Key - Value 

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## Pros and cons of SQL and NoSQL databases

https://www.softwaretestinghelp.com/sql-vs-nosql/

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| SQL | NoSQL |
| -------- | -------- |
| -/+ fixed data structure | + flexible data structures |
| + normalized data | - redundant data |
| + standard and powerful query language | - no standard interface, less powerful queries |

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| SQL | NoSQL |
| -------- | -------- |
| + commercial and community support due to age of the technology | - less support |
| + code free | + hierarchical data |
| + data retrieval speed | + handles big data |

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## Examples of queries for SQL and NoSQL databases :anguished:


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This question is the source of a number of jokes, including:

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- The truth is that NoSQL is NOT a standard. It does NOT have a specification. Of any kind.
- All it is is a term that describes a whole bunch of completely-different products.

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In reality, you have a number of ways to query NoSQL databases, including:

- Ironically, some NoSQL databases now support SQL for querying;
- Most NoSQL databases have unique custom interfaces(eg: MongoDB)
- Many NoSQL databases support (or have plug-ins to e.g. Hadoop that support) Map/Reduce style "querying".

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## That being said, here are some examples for queries

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### Selecting everything from a collection:
- SQL

- NoSQL(MongoDB)

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### Selecting with a condition
- SQL

- MongoDB

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## But switch to anything other than MongoDB and you have new syntax
## (NoSQL is a concept, not a product/language):angry:

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