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Video: SQL Basics for Beginners

https://www.youtube.com/watch?v=zbMHLJ0dY4w

Introduction to SQL

• Features

• Well defined standards

• Each query has to be written in a specific way

• Can create multiple views

Data and Database

• Database: data from user is process, stored

• Types

• Distributed Database

• Object Oriented Database

• Centralized Database

• Operational Database

• Graph Database

• NoSQL Database

• Cloud Database

• Relational Database

Popular Databases

• mongoDB

• Postgres

• Microsoft access

• Microsoft sql server

• Mysql

• Oracle

Table: collection of data in a tabular form

• Contains data values named values

• Intersection of rows and columns = cell

• Any amount of rows, set amount of columns

• Table has to have a name

• Tuples: single row of table which contains single record for that relation

• Attributes: features of an entity

• Has a name and data value

• Table constraints: restrictions defined by user when table is created

• Have to be decided during creation of table

• Check default

• Primary key

• Foreign key

• Not null

• Index

• Unique

SQL Queries

• Select statement: what part of table you want to select

• Where clause: if we need only certain records, filters through table

• And, or, not operator: just like operators in java

• Insert into: inserting new record or data into table

• Aggregate values

• Average, min, etc.

• Order by: sort result in ascending or descending order

• Null values: are null (field with no value)

• Update: modify rows in a table

• Delete: delete rows