Written by BLOGDAY Updated at Aug 16, 2024 | Reading time: 5
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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
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.
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)
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)
SDLC-Software Development Life Cycle
Domain expert(SRS documentation)
ERD(Entity Relationship Diagram)
Peter Chan-Used to design Database
SQL server performs existence check when we create relationship.
commands (DDL,DML,DQL,DCL,TCL)
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