EXPLAIN shows how the query engine plans to execute the query. possible_keys represents what all available indices are there which can be used in this query. The key column represents which index is actually going to be used out of all possible indices in this query.
SHOW TABLE STATUS WHERE name = 'index_demo' \\G;
Cap Theroem
database engine based DBMS such as mySQL, percona, MariaDB. I compare it to postgresSQL.
Things to do before sharding: Indexing, partitioning, replication
Update your database statistics often or your SQL queries will suffer (full scan or index scan)
view vs materialised view
Database Page Size and OS/FS Page Size
https://dba.stackexchange.com/questions/224969/what-is-the-relation-between-mysql-pages-and-operating-system-pages
A data could be anything like about customers, products, employees, orders, …etc. and can be in any format like text format, numeric, dates, document files, images, audio, or video.
A database is an organized collection of data.
There are many ways to organize a database and many different types of databases designed for different purposes. Within databases, tables are organized in schemas.
The database schema is its structure described in a formal language supported by the database management system (DBMS).
Schema refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases).
In a relational database, the schema defines the tables, fields, relationships, views, indexes, packages, procedures, functions, queues, triggers, types, sequences, materialized views, synonyms, database links, directories, XML schemas, and other elements.