How do I compare 2 rows from the same table (SQL Server)?

sql, sql-server, t-sql

Solution

You can join a table to itself as many times as you require, it is called a self join.

An alias is assigned to each instance of the table (as in the example below) to differentiate one from another.

SELECT a.SelfJoinTableID
FROM   dbo.SelfJoinTable a
       INNER JOIN dbo.SelfJoinTable b
         ON a.SelfJoinTableID = b.SelfJoinTableID
       INNER JOIN dbo.SelfJoinTable c
         ON a.SelfJoinTableID = c.SelfJoinTableID
WHERE  a.Status = 'Status to filter a'
       AND b.Status = 'Status to filter b'
       AND c.Status = 'Status to filter c'

Problem

I need to create a background job that processes a table looking for rows matching on a particular id with different statuses. It will store the row data in a string to compare the data against a row with a matching id. I know the syntax to get the row data, but I have never tried comparing 2 rows from the same table before. How is it done? Would I need to use variables to store the data from each? Or some other way? (Using SQL Server 2008)

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