SQL: From Basics to Advanced+ Sql interview(Beginner to Pro)

Why SQL

Store large number of records

Share huge data set among many people

Add and edit data easily

Quick and easy to find information

RDBMS TERMINOLOGY

Column   as Attribute

Row as Entity Instance

Table as Entity

AlternateKey as UniqueKey

RELATIONSHIPS Cardinality

90% of the tables in database will be linked with another tables.

10%of the tables will be independent.

There are three types of relationships between tables

one to one

one to many

many to many

Tables can have a single / multiple relationships or may not have relationships.

Structured data – 2 dimensional data Rows,Columns

PrimaryKey in one table will be given as ForiegnKey in another table to build relationship.

DATA MODELING

RDBMS

PrimaryKey & ForiegnKey with relationship between them.

1 to 1 – any PrimaryKey can become ForiegnKey

1 to many employees in a department

PK of parent table will be FK in child table

Department table Deptid(PK),DeptName,

Employees Table  Empid,EmpName,DeptId(FK)

many to many(students and teachers,patients & doctors,Hospital & Doctors)(TeacherId,TeacherName)(StudentId,StudentName,TeacherId)

New table will be created and extra column will be added(Bridge Table)

Patient Table(PatientNo(PK),PatientName,Adress),

Doctors Table(DoctorNo(PK),Name,Qualification,Salary, DateOfJoining, DateOfResigning)

Patient Doctor Table()

SDLC-Software Development Life Cycle

Requirement

Analysis & Design

Development

Testing

Release

Domain expert(SRS documentation)

Architect

SQL developers

Testers

Deployers(TL/Manager)

ERD(Entity Relationship Diagram)

Peter Chan-Used to design Database

Referential Integrity

SQL server performs existence check when we create relationship.

SELF REFERENTIAL TABLES

A table which has both PrimaryKey and ForiegnKey in it & ForiegnKey refering the primary key in the same table.

You are going to learn

commands (DDL,DML,DQL,DCL,TCL)

datatypes

constraints

CONSTRAINS

Null

Default

PrimaryKey

UniqueKey

ForiegnKey

Check

Auto Increment

views

operators

query writing

joins

sub query

derived table

Views

Indexes

Stored Procedures

Triggers

Functions

Cursors