Database design

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Database design

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DanCafeFood

Posted Wednesday, February 11, 2009 9:11 AM

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I have the following Data:

Instructors Course ID Class Company Room
Dan Smith 100 AJAX American Airlines 500
Dianne Ross 200 WPF Boeing 502
Donna White 300 LINQ Lufthansa 500
Donna White 100 AJAX Lufthansa 501

There is a one to many relationship between room and course (1 room can have
many courses)
There is a one to many relationship between Course and Teacher (1 course can be
taught by many teachers)
There is also Many to Many relationship between Company and Class

How would I design the database?

Post #654968

JestersGrind

Posted Wednesday, February 11, 2009 9:17 AM

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Hmm... This looks an awful lot like homework. Why don't you post what you think the design should look like and maybe someone will critique it?

Greg

Post #654975

Jack Corbett

Posted Wednesday, February 11, 2009 9:31 AM

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DanCafeFood (2/11/2009)

I
There is a one to many relationship between room and course (1 room can have
many courses)
There is a one to many relationship between Course and Teacher (1 course can be
taught by many teachers)
There is also Many to Many relationship between Company and Class

How would I design the database?

It looks like you already a have the basic table srtuctures defined in the statement above. You have rooms (table names should always be plural), teachers, courses (I'm assuming courses and classes are the same), and companies. Then you just need to define your relationships. A search on Many To Many relationship in database design will return many resources.

As Greg said, post what your ideas and folks will comment on them.

Jack Corbett

Applications Developer

Don't let the good be the enemy of the best. -- Paul Fleming

Check out these links on how to get faster and more accurate answers:
Forum Etiquette: How to post data/code on a forum to get the best help
Need an Answer? Actually, No ... You Need a Question
How to Post Performance Problems
Crosstabs and Pivots or How to turn rows into columns Part 1
Crosstabs and Pivots or How to turn rows into columns Part 2

Post #654996

DanCafeFood

Posted Wednesday, February 11, 2009 9:52 AM

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I wanted to paste the database diagram picture here. Is there a way to paste it.

Post #655027

DanCafeFood

Posted Wednesday, February 11, 2009 10:25 AM

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I guess there is no way to paste a database diagram here, so here is my idea:

CREATE TABLE [dbo].[tblClass](
[ClassName] [nchar](10) NULL,
[RoomName] [nchar](10) NULL
) ON [PRIMARY]

GO
ALTER TABLE [dbo].[tblClass] ADD CONSTRAINT [PK_ClassName] PRIMARY KEY CLUSTERED
(
[ClassName] ASC
)GO

CREATE TABLE [dbo].[tblCompany](
[CompanyID] [nchar](10) NULL,
[CompanyName] [nchar](10) NULL
) ON [PRIMARY]

GO
ALTER TABLE [dbo].[tblCompany] ADD CONSTRAINT [PK_CompanyID] PRIMARY KEY CLUSTERED
(
[CompanyID] ASC
)GO

CREATE TABLE [dbo].[tblRooms](
[RoomName] [nchar](10) NULL
) ON [PRIMARY]

GO
ALTER TABLE [dbo].[tblCompany] ADD CONSTRAINT [PK_RoomName] PRIMARY KEY CLUSTERED
(
[RoomName] ASC
)GO

CREATE TABLE [dbo].[tblTeachers](
[CompanyId] [nchar](10) NULL,
[Teacher] [nchar](10) NULL
) ON [PRIMARY]

GO

ALTER TABLE [dbo].[tblTeachers] ADD CONSTRAINT [PK_Teacher] PRIMARY KEY CLUSTERED
(
[Teacher] ASC
)GO

CREATE TABLE [dbo].[tblCompClass](
[CompanyId] [nchar](10) NULL,
[ClassID] [nchar](10) NULL
) ON [PRIMARY]

GO

ALTER TABLE [dbo].tblCompClass] WITH CHECK ADD CONSTRAINT [FK_tblCompClass_Company] FOREIGN KEY([CompanyID])
REFERENCES [dbo].[tblCompany] ([CompanyID])
GO

ALTER TABLE [dbo].[tblCompClass] CHECK CONSTRAINT [FK_tblCompClass_Company]
GO

ALTER TABLE [dbo].[tblCompClass] WITH CHECK ADD CONSTRAINT [FK_tblCompClass_tblClass] FOREIGN KEY([ClassName])
REFERENCES [dbo].[tblClass] ([ClassName])
GO

ALTER TABLE [dbo].[tblCompClass] CHECK CONSTRAINT [FK_tblCompClass_tblClass]
GO

ALTER TABLE [dbo].[tblTeacher] WITH CHECK ADD CONSTRAINT [FK_tblTeacher_tblCompany] FOREIGN KEY([CompanyID])
REFERENCES [dbo].[tblCompany] ([CompanyID])
GO

ALTER TABLE [dbo].[tblTeacher] CHECK CONSTRAINT [FK_tblTeacher_tblCompany]
GO

ALTER TABLE [dbo].[tblClass] WITH CHECK ADD CONSTRAINT [FK_tblClass_tblRooms] FOREIGN KEY([RoomName])
REFERENCES [dbo].[tblRooms] ([RoomName])
GO

ALTER TABLE [dbo].[tblClass] CHECK CONSTRAINT [FK_tblClass_tblRooms]
GO

Post #655066

Jack Corbett

Posted Wednesday, February 11, 2009 10:46 AM

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Looks like it would work. One of my preferences is to to use an identity column as the primary key (adding a unique constraint on the true primary key) and then use that id column as the foreign key in other tables. If you do not do this and room names can change you need to make sure CASCADE updates on your relationships.

Post #655091

DanCafeFood

Posted Wednesday, February 11, 2009 10:50 AM

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Jack,
Thanks for the reply. It makes sense to add the ID identity column in Rooms table. My question is, does this design looks too normalized?

Post #655095

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