MSSQL - Compare data from 1 table to multiple tables

Question

I need to do a comparison from one table (which is a CRM inventory) to 4 other tables (which are webserver inventories). Currently I am using the following query, but I am getting duplicates and false positives due to the fact it is rechecking the first table against each other table and simply outputting the results every time then displaying them all together:

SELECT sc.Client,
       ws.[Host Header],
       ws.[IP Address],
       ws.[Status]
FROM   sc
       FULL JOIN ws
              ON sc.Urls = ws.[Host Header]
WHERE  sc.Client IS NULL
        OR ws.[Host Header] IS NULL
        OR sc.Urls <> ws.[Host Header]
UNION
SELECT sc.Client,
       ws2.[Host Header],
       ws2.[IP Address],
       ws2.[Status]
FROM   sc
       FULL JOIN ws2
              ON sc.Urls = ws2.[Host Header]
WHERE  sc.Client IS NULL
        OR ws2.[Host Header] IS NULL
        OR sc.Urls <> ws2.[Host Header]
UNION
SELECT sc.Client,
       ws3.[Host Header],
       ws3.[IP Address],
       ws3.[Status]
FROM   sc
       FULL JOIN ws3
              ON sc.Urls = ws3.[Host Header]
WHERE  sc.Client IS NULL
        OR ws3.[Host Header] IS NULL
        OR sc.Urls <> ws3.[Host Header]
UNION
SELECT sc.Client,
       ws4.[Host Header],
       ws4.[IP Address],
       ws4.[Status]
FROM   sc
       FULL JOIN ws4
              ON sc.Urls = ws4.[Host Header]
WHERE  sc.Client IS NULL
        OR ws4.[Host Header] IS NULL
        OR sc.Urls <> ws4.[Host Header] 

Can someone point me in the right direction? I want to return only the distinct results from each of the tables that are null or mismatching in the sc.Client and ws.[Host Header] fields and there are no duplicates between the 4 webserver tables.

Thanks!

Answer 1

Why don't you try first to perform a UNION between all ws tables and then perform FULL JOIN of sc table against the table expression resulting from the UNION operation? – Giorgos Betsos

This was dead on! I adjusted my query to the following and everything worked great!

SELECT sc.Client, ws.[Host Header], ws.[IP Address], ws.[Status]
FROM sc full outer join (select * from ws1 union all select * from ws2 union all select * from ws3 union all select * from ws4) as ws ON sc.Urls = ws.[Host Header]

Thanks!