> For the complete documentation index, see [llms.txt](https://liuzhenglaichn.gitbook.io/system-design/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://liuzhenglaichn.gitbook.io/system-design/basics/sql-vs-nosql.md).

# SQL vs NoSQL

SQL: relational database store data in tables which are formed in rows and columns. 

NoSQL: 

* key-value
* document
* graph

## High level differences

### Storage

SQL: table

NoSQL: key-value, document, graph.

### Schema

SQL: fixed

NoSQL: dynamic

### Querying

SQL: uses SQL (structured query language)

NoSQL: UnQL (unstructured query language).

### Scalability

SQL: vertically scalable. Hard to horizontally scale

NoSQL: horizontally scalable.

### Reliability or ACID Compliancy (Atomicity, Consistency, Isolation, Durability)

SQL: ACID compliant

NoSQL: sacrifice ACID compliance for performance and scalability.

## Ideal Applications

<https://www.sitepoint.com/sql-vs-nosql-differences/>

### Projects where SQL is ideal

* logical related discrete data requirements which can be identified up-front
* data integrity is essential
* standards-based proven technology with good developer experience and support.

### **Projects where NoSQL is ideal**

* unrelated, indeterminate or evolving data requirements
* simpler or looser project objectives, able to start coding immediately
* speed and scalability is imperative.

<https://github.com/donnemartin/system-design-primer#sql-or-nosql>

* Rapid ingest of clickstream and log data
* Leaderboard or scoring data
* Temporary data, such as a shopping cart
* Frequently accessed ('hot') tables
* Metadata/lookup tables


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