Relationships As A Table
Jul 20, 2005
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
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Jul 20, 2005
Hi,Does anyone have any suggestions on the best to go about enforcing arelationship between two tables that exist within separate databaseson the same SQL Server instance.
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May 19, 2008
Hi,
I'm working on a database for which I require to have a lot of relations from my Persons table to other tables. I will need my primary key in those other tables: about 10 to 15 tables, to be able to relate to my persons data.
I believe this means I have 10 to 15 clustered indexes on this table.
Is this the right way of working? I know too many of this relations to other tables will have impact on performance concerning insert and updates.
But I noticed in the adventureworks example it works just this way for the products table.
What is the max limit of this kind of relations? (for reasonably good performance)
Should I use triggers instead? - for those with the least user interaction?
Thanks in advance,
Mike
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Jan 26, 2004
Hello,
I am looking to print the table structure of a Microsoft SQL Server 7 database through the Enterprise Manager Utility. I would like to print it to a plotter but the print options in the Enterprise Manager are inadequate. I believe I will need to use another program to manipulate the object prior to plot due to its size. I have the following tools available:
VB6
Autocad
(Do not have Adobe Writer)
Is there a way to get this print object to Autocad or even as a bitmap?
Thanks is advance,
bds
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Nov 12, 2007
What is the iso sql query to get the relationships between all tables in a db?
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Aug 3, 2006
I have spend days researching this and found others with the exact same
problem but there are no useful replies as people don't seem to
understand our problem. Please read this carefully...
What is the best way to create relationships between new SQL tables? For example, say I want to create a new database with tables for Customer, Orders and Details, how to I relate these tables?
- Edit via the Dataset designer in Visual Studio 2005?
- Use the Server Explorer's Table designer in Visual Studio? (not sure how to use the 'relationship' icon)
- Use SQL Server Managment Studio Express (SSMSE) Database Diagram
- Something else?
I am using Visual Studio 2005 Standard and SQL Server 2005 Express (SP1).
I created a new database in Visual Studio's Server Explorer and then used the Table Designer to create two new Tables (Customers and Orders). I then assigned primary keys but I don't know the best way to relate the tables.
If I create and edit a new dataset, I can graphically drag a relationship between the tables. HOWEVER, this relationship isn't recognized by SQL Server Management Studio Express (SSMSE). I found this out when I tried to create a database diagram, none of the relationships appear in SQL?! This would cause problems when I want to deploy the database to my client.
If however, I START in SSMSE and create the tables there, then open a Database Diagram in SSMSE and graphically link the tables, then Visual Studio will see all the relationships.
I thought it was supposed to be a seamless integration between Visual Studio 2005 and SQL Server 2005. Am I missing something?
Richard
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May 9, 2007
I am trying to update 2 tables at the same time by adding new records to them and then making sure that they are related on my junction table?
Table1
packageID
Packagename
Table2 (JunctionTable)
PackageID
JobID
Table3
JobID
JobName
And I want to create a new package and new Job Name at the same time I would need to make multiple insert statements
First take care of the new Package
INSERT INTO Table1 (PackageName) Value (@PackageName)
Then Take Care of the JobName
INSERT INTO Table3 (JobName) Value (@JobName)
Finally marry the two together
but how?
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Mar 29, 2008
Can I programatically access all relationships for a sql table? I know i can do this in the table designer ...
---Jim
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May 30, 2008
:eek: =>First ,2nd ,3rd normalization
=>Data Integrity
=>Mappings-
1 1:1 mappings
2 1:2 mappings
3 Many :MAny mappings
=>Establish relationship
1.Simple
2.Complex
3. Multiple
Defination of these all or details with subjects also
pls reply me soon
it is urgent for me
thanks in advance
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Jul 23, 2005
What is the best way to setup relationships between one lookup tableand many other tables. The tables did not have any lookup tablerelationships which I am adding. One lookup table is used for same datain several different places.To use one lookup tables with several tables, I had to disable "CascadeUpdate" and only have "enforce relationships for updates and inserts"checked.Any pros/cons?Thanks in advance.P
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Nov 9, 2005
Hello,I want to be able to view data from 3 tables using the JOIN statement, butI'm not sure of how to do it. I think i don't know the syntax of the joins.Iimagine this is easy for the experienced - but Im not.Allow me to explain:I have 2 Tables: PERSON and SIGNPERSON------PersonNo int (Primary Key)Name varchar(50)StarSign intFavFood intSIGN----StarSign int (Primary Key)StarSignName varchar(50)Relationship: SIGN has a one-to-many relationship with PERSON. The linkingfield is called 'StarSign'.Question 1:I want to display all the peoples names, and their star sign (whether theyhave one or not).Answer 1:SELECT PERSON.Name, SIGN.StarSignNameFROM PERSON LEFT OUTER JOIN SIGN ON PERSON.StarSign = SIGN.StarSign;No problems there. But now I want to do the same thing, but have theirfavourite food displayed as well. So an additional table is needed:FOOD----FavFood int (Primary Key)FavFoodName varchar(50)Relationship: FOOD has a one-to-many relationship with PERSON. The linkingfield is called 'FavFood'.Question 2:I want to display all the peoples names, their star signs (whether theyhave one or not), and their favourite food (whether they have one or not).Answer 1:???I'm not sure what to do. Notice that I want to use an LEFT OUTER JOIN so ALLthe rows from table PERSON will appear 'irrespective' of whether they haverelated records in the other tables.Jack.
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Mar 26, 2008
I'm building an application that tracks courses and equivalent courses. For example, say I have course A which a user should get credit for if they have taken equivalent courses. So if a user has taken (course B or course C) AND (course D or course E) he should get credit for Course A. What's the best way to setup a SQL table to create these type of equivalent relationships?
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Aug 22, 2007
Hi,
I'm looking for a query I can use to alter table relationships. What I want to do in particular, is to set every relationship to cascade on update. Can anyone point me out to a solution? MSDN seems very vague in this subject.
Thanks,
Tiago
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May 5, 2015
I'm using Sql Server 2012 Enterprise and have a database with over 400 tables. I am looking at one diagram which contains about 20 (or so) tables and their relationships. When I right-click on a relationship line I only see information about which tables are connected on that line but not on which fields. Can I get that information from the Diagram or can I only get that from the sys tables?
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Apr 11, 2006
Hello again,
I'm going through my tables and rewriting them so that I can create relationship-based constraints and create foreign keys among my tables. I didn't have a problem with a few of the tables but I seem to have come across a slightly confusing hiccup.
Here's the query for my Classes table:
Code:
CREATE TABLE Classes
(
class_id
INT
IDENTITY
PRIMARY KEY
NOT NULL,
teacher_id
INT
NOT NULL,
class_title
VARCHAR(50)
NOT NULL,
class_grade
SMALLINT
NOT NULL
DEFAULT 6,
class_tardies
SMALLINT
NOT NULL
DEFAULT 0,
class_absences
SMALLINT
NOT NULL
DEFAULT 0,
CONSTRAINT Teacher_instructs_ClassFKIndex1 FOREIGN KEY (teacher_id)
REFERENCES Users (user_id)
)
This statement runs without problems and I Create the relationship with my Users table just fine, having renamed it to teacher_id. I have a 1:n relationship between users and tables AND an n:m relationship because a user can be a student or a teacher, the difference is one field, user_type, which denotes what type of user a person is. In any case, the relationship that's 1:n from users to classes is that of the teacher instructing the class. The problem exists when I run my query for the intermediary table between the class and the gradebook:
Code:
CREATE TABLE Classes_have_Grades
(
class_id
INT
PRIMARY KEY
NOT NULL,
teacher_id
INT
NOT NULL,
grade_id
INT
NOT NULL,
CONSTRAINT Grades_for_ClassesFKIndex1 FOREIGN KEY (grade_id)
REFERENCES Grades (grade_id),
CONSTRAINT Classes_have_gradesFKIndex2 FOREIGN KEY (class_id, teacher_id)
REFERENCES Classes (class_id, teacher_id)
)
Query Analyzer spits out: Quote: Originally Posted by Query Analyzer There are no primary or candidate keys in the referenced table 'Classes' that match the referencing column list in the foreign key 'Classes_have_gradesFKIndex2'. Now, I know in SQL Server 2000 you can only have one primary key. Does that mean I can have a multi-columned Primary key (which is in fact what I would like) or does that mean that just one field can be a primary key and that a table can have only the one primary key?
In addition, what is a "candidate" key? Will making the other fields "Candidate" keys solve my problem?
Thank you for your assistance.
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May 29, 2007
Ok, so I open up a book on beginning sql and it discusses relationships.There is something that appears wrong. I am not understanding how the book is describing the one to one relationship. In it's figure, it shows that the same agency can have two different artist id's. But according to it's definition of one to one list can be related from both tables.Can someone explain this further please?Thanks in advance.
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Aug 8, 2007
How do you show many to many relationships in ASP.NET with datasources?
I can retrieve the information from the database easily but I can't manage to save that information into a variable so that i can then call for only information in the M2M table related to the ID Key I want. For example..1 <asp:Label ID="lblTestLabel" Text='<%# DataBinder.Eval(Container.DataItem, "title_id") %>' Runat="server" />
2
3 <script language="VB" runat="server">
4 sub Page_Load(sender as Object, e as EventArgs)
5 Dim lblTitleID As Label = Repeater1.FindControl("lblTestLabel")
6 Response.Write(lblTitleID.text)
7 End Sub
8 </script>
When I try to run this script it dosn't work and I get the error:
System.NullReferenceException: Object reference not set to an instance of an object.
For line 6 of the code above. Is there a way to just retrieve information from a datasource without storing information into a label first?
PS: I use sqldatasource tags to retrieve information like:1 <asp:SqlDataSource ID="DataSet1" runat="server"
2 ConnectionString="Driver={MySQL ODBC 3.51 Driver};server=localhost;database=;user=;pwd=;option=3;"
3 ProviderName="System.Data.Odbc"
4 SelectCommand="Select * from titles order by title_id">
5 </asp:SqlDataSource>
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Aug 10, 2007
Can someone help me sort something out. Suppose we have two tables in a database.One is named Person, and one is named Birthday. Is this a many to many relationshipor a 1 to many relationship?
Person has many birthdays. Example. Joe Schmoe has a birthday for every year of his life. birthday(7/11/1976) has many People (Many people have a birthday on 7/11/1976.
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Feb 2, 2004
Is there any easy way of getting all the relationships for the tables in aSQL server db? I've looked through Google and the Books online but I'm barely scratching the surface on the systables. I know I can go to each individual table and get the dependencies or even print out the diagram through Enterprise Manager but I really don't want to have to type out all the primary/foreign keys for 100+ tables. Any help on getting this data either through a 3rd party software or querying the systables would be great.
THT
DMW
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Mar 21, 2001
We have a table with approximately 150 colums and 2/3 of them are bit datatypes. We do not expect much activity on this table. Does it make sense to separate it into a few tables instead of 1 with one-to-one relationships? Will the join(s) significantly slow down our web application? Thank you
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Aug 6, 2004
My hosting servers have "myLittleAdmin" installed. I am new to ms sql I have some experience with Access but I have never set up Relationships inside the database server. I have always just relied on my application logic to call the relations. What is the benefit to setting up relationships in sql, if any?
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Nov 11, 2004
Is there a tool in Enterprise manager to list out the one to many & many relationships with a database?????:?:
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Feb 1, 2007
Hey, I have SQL Sever Enterpise Manager. I am new at this company and I need to know the relationships between ALL the tables. Is there anywhere I can go to view all the primary keys and the relationships?
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Jun 1, 2007
I am viewing tables in the ‘object explorer’- I can see the tables. If I open it up I can see columns, keys, constraints etc…
So I can see they key… can I tell which table/field the foreign key is connected to?
thanks
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Oct 17, 2007
Hello,
I have 3 tables. Posts, PostsTags and Tags.
This is a many to many relationship.
So PostsTags has the following columns:
PostId (PK) and TagId (PK)
I always did that way in SQL 2005.
In some examples I see PostsTags have 3 columns:
PostTagId(PK), PostId (FK), TagId (FK)
Should I use it this way, instead?
Thanks,
Miguel
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Jul 13, 2006
Is it possible to have 2 different databases and create relationships inbetween the two? I am thinking about way down the road and the size of the databases and I believe that I need to split my data into multiple databases to keep from running into the size limitations.
Davids Learning
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May 29, 2007
Ok, so I open up a book on beginning sql and it discusses relationships.
There is something that appears wrong. I am not understanding how the book is describing the one to one relationship. In it's figure, it shows that the same agency can have two different artist id's. But according to it's definition of one to one list can be related from both tables.
http://foo.gearsector.com/foo/instr_scrns/oneToMany.gif
Can someone explain this further please?
Thanks in advance.
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Apr 1, 2008
How can I use with relationShips in SQl?
Tamir BLoch .
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Apr 3, 2007
Hello!
I have a really small database in terms of number of objects, but very big in terms of data (possibly millions of records). I always try to design my databases to be in the 3rd normal form (at least I hope they are!), but sometimes (for databases consisting of just a few tables) maintaining M:N relationships looks like an over-bloated approach to me... Let's see an actual example. I have a table like this:
Code SnippetCreate table [Airfares]
(
[OriginCity] Char(3) NOT NULL,
[DestCity] Char(3) NOT NULL,
[FareDate] Datetime Default getdate() NOT NULL,
[Price] Decimal(9,2) Default 0 NOT NULL,
[PriceChange] Decimal(9,2) Default 0 NOT NULL,
[Wrong] Bit Default 0 NOT NULL,
Primary Key ([OriginCity],[DestCity],[FareDate])
)
go
Now, at first there also was an Airline nvarchar(50) field, which stored the airline name. But now the client requested to store fares for a few airlines if it's the same price and city pair. This way we can have 3 airlines offering the same price on the same itinerary for example. So I added a dictionary table called Airlines:
Code SnippetCreate table [Airlines]
(
[AirlineCode] Char(2) NOT NULL,
[Name] Nvarchar(50) NOT NULL,
Primary Key ([AirlineCode])
)
go
Now, there are two things I can do. We are obviously dealing with the M:N relationship type here. I can either add another nvarchar column in the first table, like Airlines nvarchar(255) and store something like 'AA,AB,AC' there - those would be airline codes. OR I could do it the proper way and create a cross-reference table which will connect both Airfares and Airlines tables (this will store as many records as there are airlines for that particular itinerary, offerring the same price):
Code SnippetCreate table [AirfareAirlines]
(
[AirlineCode] Char(2) NOT NULL,
[OriginCity] Char(3) NOT NULL,
[DestCity] Char(3) NOT NULL,
[FareDate] Datetime Default getdate() NOT NULL,
Primary Key ([AirlineCode],[OriginCity],[DestCity],[FareDate])
)
go
But this is starting to look overly complicated, isn't it? The pros of this are I'm going to get real relationships, referential integrity, etc., but cons are more difficult code to query all this. What would you do? Do we really need referential integrity everywhere? Are there times when we're better not using relationships? I have seen many programmers skip referential integrity before, which always made me think they are missing something important in a Relational Database Management System.
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Feb 13, 2008
Hi
How I can get to see the relationships, like in access, in sql 2005?
Thank,
K
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Mar 16, 2008
Ok - I am still a bit weak on SQL. My understanding of FK relationships in a database are to reinforce the data integrity - Correct? For example, does it make sure that the id given for SiteID does indeed exists. Can it link tables like JOIN in select statements? If not, is there any gains by creating them, such as performance?
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Feb 15, 2004
I'm having some trouble working out how to query some data. Rather than explain up front, here's some examples of what I want to achieve:
*******************************************************
I've got a structure which looks vaguely like this:
[ANCESTORS]
Grandparent
Parent
Child
If limit by grandparents, then I only get the lineage for that particular grandparent. I.e.:
SELECT *
FROM [ANCESTORS]
( some sort of joins here )
Where Grandparent.Name = 'Cybill'
This would return all of the children of 'Cybill' and their children. Now, if I use the following query:
SELECT *
FROM [ANCESTORS]
( some sort of joins here )
Where Child.Name = 'Jean'
This would return Jean's parents + the parents of Jean's parents (Jean's grandparents).
Likewise, if I enter:
SELECT *
FROM [ANCESTORS]
( some sort of joins here )
Where Parent.Name = 'Ron'
Then I would get Ron's parents and also his children.
*******************************************************
So, as you can see, at first it appears that I'm after a LEFT JOIN - meaning that the grandparents don't need to have child records to be returned, but, then it turns out that I need INNER JOINS - to limit grandparents when I choose children.
Can anybody see my dilemma here?
Mark-up ASP.net posts here
MarkItUp.com
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Nov 27, 2005
Hi
I am using the Web Matrix Project to write a .NET
application. I have set up a database using MSDE which I
accessed through the Web Matrix Project to start with. I have now
found the Web Data Administrator which I use to backup my database and
help to transfer it to the Server where I hope to run this application
(if I ever get it finished!).
I need to set up some relationships between database tables but cannot
see a way to do this. SQL Server Books on Line referes to
Enterprise Manager which I believe ships with the full MS SQL Server
package (and costs a package). I am doing this on a
shoe-string. Any ideas on how to do it?
Thanks in advance.
Mike
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