同一表中的相互匹配的SQL Server查询（2012）

Question

We have a table with following columns in Tenants Table.

TenantID
Name
address
Current_Bedrooms
Bedrooms_Needed
Current_City
City_Needed

For a given row, how can we write a query that will find the match the bedrooms_Needed with Current_Bedrooms (same with city) in other rows

example

Select * from Tenants where Current_Bedrooms = Bedrooms_Needed and TenantID = 1234

Answer 1

It sounds like you want the tenants to 'swap' with eachother? You can join the tenants table with itself (aliased as t1 and t2 ), while specifying the matching criteria as the join condition:

Select T1.Name As TenantFrom, t2.Name AS TenantTo
from Tenants t1
INNER JOIN Tenants t2
ON t1.Bedrooms_Needed = t2.Current_Bedrooms 
AND t1.City_Needed = t2.Current_City
AND t1.TenantID <> t2.TenantID
WHERE t1.TenantID = 1234;

The tenant id exclusion is to prevent self-matches in the event of the tenant living in an exact match already.

Edit, Re Mutual Matches

In order to find pairs of mutually matching tenants, you will need to add the reciprocal criteria as additional filters:

Select T1.Name As TenantFrom, t2.Name AS TenantTo
from Tenants t1
INNER JOIN Tenants t2
ON t1.Bedrooms_Needed = t2.Current_Bedrooms 
AND t1.City_Needed = t2.Current_City
AND t1.Current_Bedrooms = t2.Bedrooms_Needed
AND t1.Current_City = t2.City_Needed 
AND t1.TenantID <> t2.TenantID
WHERE t1.TenantID = 1234;