SQL Overview

Table, Fields and Rows

Table is a collection of data. It consists of fields. Field is a column in a table that contains data of the table. Record or row is individual entries containing data of a table. 

SQL Constraints

Constraints are rules enforced on columns or tables. The idea is to increase accuracy and reliability of data. 

• Not null
• Default
• Unique
• Primary Key
• Foreign Key
• Check
• Index

Different types of SQL

SQL : Query language operates on sets

PL/SQL : proprietary procedural language used by Oracle

PL/pgSQL : proprietary procedural language used on PostgreSQL

TSQL : propritetary procedural language used by Microsoft in SQL Server

http://stackoverflow.com/questions/1043265/what-is-the-difference-between-sql-pl-sql-and-t-sql

SQL Server vs. Oracle

In comparison SQL is much easier to use than Oracle mainly because oracle has lot more configurations comparatively. Also SQL Server integrates much easily with .NET Framework.

http://stackoverflow.com/questions/689807/sql-server-vs-oracle

References

http://www.tutorialspoint.com/sql/sql-rdbms-concepts.htm