MySQL vs. PostgreSQL vs. Redis

MySQL vs. PostgreSQL vs. Redis
MySQL is a popular open source relational database management database, that is based on SQL (structured query language).

PostgreSQL is an advanced open source relational database management database that too uses the SQL but also uses the advanced features that makes it more powerful.

So What makes it advanced and what are the radical difference in between PostgreSQL and MySQL?

ACID Compliance
ACID (Atomicity, Consistency, Isolation, and Durability) in the database is very imperial to its existence. What it means is that " no data is lost or miscommunication".

PostgreSQL is fully ACID complaint whereas MySQL is partially ACID complaint with only certain engines.
SQL Compliance

SQL compliance is necessary so that database can be transferred from one database to another. For example. Oracle to PostgreSQL/MySQL or vice versa.

PostgreSQL is largely SQL compliant whereas MySQL is partially complaint like CHECK constraint is not supported in MySQL.
Performance
PostgreSQL is used in large systems where read and write speeds are crucial.
For example: Geospatial data support, Data Warehousing and data analysis applications that require fast read/write speeds.

MySQL is a chosen for web based projects that need a database simply for straightforward data transactions

REDIS:
REDIS is acronym for “Remote + Dictionary+ Server”.
• Store data in key value pairs.
• It is an open source and NO-SQL database.
• use data-structures to store data like set, list, string etc.
• Interaction with data is through the command basis.
• It is an in-memory database it means it keeps the data in cache. Therefore it is super-fast. Although it has option to write in disk.
• Can be used as a second database to make query faster.
• can be used as a caching system or full-fledged database.