Monday, November 21, 2005

Returning comma seperated details from a table ...

I saw an question in one of the SQL newsgroup which I visit frequently (offlate). That person is having a problem with retriving data from a table. Let me explain it in detail.

Sample table structure:

Create table empTest
(
[Id] int identity,
Contact varchar(100),
Employee_Id int
)
Go


Let us populate few records into the table:

Insert into empTest (Contact, Employee_Id) values ( 'vmvadivel@gmail.com', 101)
Insert into empTest (Contact, Employee_Id) values ( '04452014353', 101)
Insert into empTest (Contact, Employee_Id) values ( 'vmvadivel@yahoo.com', 102)
Insert into empTest (Contact, Employee_Id) values ( '9104452015000', 102)
Go

And now, as you could see each employee has more than one contact details. So if you query the table as Select * from EmpTest it would list couple of records for each employee. Instead of this won't it be nice if we could generate comma seperated contact details for each employee. i.e., There would be only one record for an employee.

Something like this, (Employee_Id, Contact )

101 vmvadivel@gmail.com, 04452014353
102 vmvadivel@yahoo.com, 9104452015000
etc.,


Solution:

-- Temp variable
Declare @strContact varchar(8000)

-- Build the comma seperated contact list
Select @strContact = Coalesce(@strContact + ', ', '') + ET.Contact From empTest ET where ET.Employee_Id = 101

--Display the comma seperated contact list
Select @strContact


This above code snippet would work for a given employee id. Now this can generalized to work for all employee id as shown below:

Create function dbo.GetEmpDetails(@EmpID int)
Returns Varchar(8000)
As
Begin
Declare @Contact varchar(8000)
Select @Contact = Coalesce(@Contact + ', ', '') + ET.Contact From empTest ET
Where ET.Employee_Id = @EmpID

Return @Contact
End
Go


Select distinct Employee_ID, dbo.GetEmpDetails(Employee_Id) as ListOfContacts From empTest
Go


To be frank I got the base logic from an article in 4guysfromrolla.com and customized it according to our need here.

9 comments:

Anonymous said...
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Anonymous said...

Is there any way you could do the same query in Oracle?

Vadivel said...

Hmm I don't have much of Oracle experience.. I am sorry.

Parameshwaran.K(Param) said...

it's good that you have done this but don't you think that it will affect the performance issue.can you tell me why & when this would be required?

Vadivel said...

Param, surely this would have a performance hit. These kind of manipulation would be better if done on the client side rather than in the T-SQL part.

But as I said, I have provided the query which that user was looking for. Needless to say one other guy have already warned about this performance stuff.

Matija Lah said...

I suggest you warn potential users of the function of the caveats that lurk beneath this fairly simple method.

See this post for more details:
http://milambda.blogspot.com/2005/07/return-related-values-as-array.html

Vadivel said...

Yeah you are right Matija. Thanks for posting your link here.

R said...

Thanks.. was a great help...

Anonymous said...

Thanks for the hint. Concetenation is commonly used and such methods are frequently required by sql developers. I recently found one using XML PATH() at http://www.kodyaz.com/articles/concatenate-using-xml-path.aspx