DBMS SQL

Structured Query Language, popularly known as SQL is a domain specific language used to manage data in relational database management systems (RDBMS).

It allows the user to perform operations such as create, delete etc. on tables in database
It also allows operations such as read, insert, update, delete etc. on the data stored in the tables.
All popular relational database management softwares such as MySQL, PostgreSQL, Oracle, Microsoft Access, IDBM Db2, SQLite etc. use SQL to manage the database.
SQL is a simple english like language which is used to query the database to perform various operations on the database.

Rules for a Better SQL Schema

Only use lowercase letters, numbers and underscores for database, schema, column and table name.
Use simple & meaningful, table and column name. This is because sometimes, we refer the attribute of a table from another table as foreign key.
SQL is not a case sensitive language, however the keywords used in the SQL query are generally written in uppercase.
Using SQL queries you can perform various operations on the database.

When a SQL statement executes, system first performs various checks such as syntax check, semantic check, shared pool check on the SQL query during parsing phase.
In the second phase, which is also known as hard parsing phase, system performs query optimization and generate various execution plans.
In the next phase, row source generator software receives the optimal execution plan and generate a iterative plan that is used by the database.
Last step is execution of the query based on the iterative plan generated in the previous step.