Question

The table consists of columns user1, user2, connectionStrength and the example records are the following:

A,B,0.2
A,C,0.5
A,G,0.1
B,C,0.8
W,Q,0.4
G,Q,0.5

I would like to retrieve all users within the defined degree of connection for the selected user and then draw a graph of connections. The question however is how to select all the records from the table that fulfill the condition. For example if user A is selected and the degree is set to 2 the following records from the example should be selected:

A,B,0.2
A,C,0.5
A,G,0.1
B,C,0.8
G,Q,0.5

The example above is hypothetical. In reality there are more than 200M connections in the database I work on and currently I use C# and Microsoft SQL Server 2008 for the analysis.

Does anyone know how to write a function (string GetQuery(string selectedUser, int degreeOfConnection)) to compose a query which returns all the records that fulfill the condition (degree of connection for the selected user)?

Edit #1

I tried to get connections by executing recursive query the following way:

WITH user_connections(user1, user2, link_strength, Level)
AS
(
SELECT user1, user2, link_strength, 0 AS Level FROM [dbo].[monthly_connections] AS mc WHERE user1 = '1ADF1126F26B4AD4441A3C552FCE04A4F7A79760'
UNION ALL
SELECT mc.user1, mc.user2, mc.link_strength, Level + 1 FROM [dbo].[monthly_connections] AS mc INNER JOIN user_connections AS uc ON uc.user2 = mc.user1
)
SELECT user1, user2, link_strength FROM user_connections OPTION(MAXRECURSION 1)

The query has been executing for more than 40 minutes so far so I would be very thankful if anyone could just check if the statement is composed correctly.

Thank you!

Answer 1

SQL 2005 and up allows you to create recursive queries using Common Table Expressions. The samples in the documentation should be enough to get you started.