SQL and NoSQL databases

  Concept Of  SQL and NoSQL databases.

    A database is information that is set up for easy access, management and updating. Computer databases typically store aggregations of data records or files that contain information, such as sales transactions, customer data, financials and product information.

    Databases are used for storing, maintaining and accessing any sort of data. They collect information on people, places or things. That information is gathered in one place so that it can be observed and analyzed. Databases can be thought of as an organized collection of information.

SQL :-

• RELATIONAL DATABASE MANAGEMENT SYSTEM (RDBMS)
• These databases have fixed or static or predefined schema
• These databases are not suited for hierarchical data storage.
• These databases are best suited for complex queries
• Vertically Scalable
• Follows ACID property
• Examples: MySQL, PostgreSQL, Oracle, MS-SQL Server, etc.

NoSQL :-

• Non-relational or distributed database system.
• They have dynamic schema
• These databases are best suited for hierarchical data storage.
• These databases are not so good for complex queries
• Horizontally scalable
• Follows CAP(consistency, availability, partition tolerance)
• Examples: MongoDB, GraphQL, HBase, Neo4j, Cassandra, etc.

Order Of Execution Of Clauses

1. FROM - Tables are joined to get the base data.
2. WHERE - The base data is filtered.
3. GROUP BY - The filtered base data is grouped.
4. HAVING - The grouped base data is filtered.
5. SELECT - The final data is returned.
6. ORDER BY - The final data is sorted.
7. LIMIT - The returned data is limited to row count.