relationships as a table

[Vinodh Kumar P]

I have the tables tblEmployees and tblProjects.
tblProjects has one column called Percentagetime, to hold the percentage of
time by an employee for a project.

My Question : Why should we introduce a 3rd table called
tblProjectsAndEmployees?
tblProjectsAndEmployees will have
1)EmployeeNumber(PrimaryKey in tblEmployees)
2)ProjectNumber(Primary key in tblProjects)
3)PercentageTime

Having only the tblEmployees and tblProjects is not sufficient?
Kind Regards,
Vinodh Kumar P

[Erland Sommarskog]

Vinodh Kumar P (vi****@here.com) writes:

I have the tables tblEmployees and tblProjects. tblProjects has one
column called Percentagetime, to hold the percentage of time by an
employee for a project.

My Question : Why should we introduce a 3rd table called
tblProjectsAndEmployees?
tblProjectsAndEmployees will have
1)EmployeeNumber(PrimaryKey in tblEmployees)
2)ProjectNumber(Primary key in tblProjects)
3)PercentageTime

Having only the tblEmployees and tblProjects is not sufficient?

As long as an employee only works on one single project it is. Or a project
never can be staffed by more than one employee.

But in real life an employee works on more than project, and project have
several members. Then you have a many-to-many relation, and the typical
way to sort that out is to introduce a linking table.

--
Erland Sommarskog, SQL Server MVP, es****@sommarskog.se

Books Online for SQL Server SP3 at
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