Selecting Override Record(s) - sql-server

Question

Selecting records with column value NOT NULL vs one that are NULL
It sounds like a typical SELECT * FROM Table WHERE Column IS NOT NULL...but not quite
Below is a table that represents a portion of data that I need to work with.
<table>
<tr>
<td align="center">Index</td>
<td align="center">A</td>
<td align="center">B</td>
<td align="center">C</td>
</tr>
<tr>
<td align="center">0</td>
<td align="center">NULL</td>
<td align="center">NULL</td>
<td align="center">NULL</td>
</tr>
<tr>
<td align="center">1</td>
<td align="center">NULL</td>
<td align="center">NULL</td>
<td align="center">1</td>
</tr>
<tr>
<td align="center">2</td>
<td align="center">NULL</td>
<td align="center">1</td>
<td align="center">NULL</td>
</tr>
<tr>
<td align="center">3</td>
<td align="center">NULL</td>
<td align="center">1</td>
<td align="center">1</td>
</tr>
<tr>
<td align="center">4</td>
<td align="center">1</td>
<td align="center">NULL</td>
<td align="center">NULL</td>
</tr>
<tr>
<td align="center">5</td>
<td align="center">1</td>
<td align="center">NULL</td>
<td align="center">1</td>
</tr>
<tr>
<td align="center">6</td>
<td align="center">1</td>
<td align="center">1</td>
<td align="center">NULL</td>
</tr>
<tr>
<td align="center">7</td>
<td align="center">1</td>
<td align="center">1</td>
<td align="center">1</td>
</tr>
</table>
Index 0 record represent the default record that everyone would use if there was no override value for A, B, or C
I am always querying with values for A, B & C but if nothing is found I want the NULL record OR NULL value combination.
By the way I am trying to do this SQL-Server 2005.
I have been trying something like
SELECT * FROM Table
WHERE (A = 1 OR A IS NULL) OR (B = 1 OR B IS NULL) OR (C = 1 )
The actual query is a cross join of 4 tables...so the table of values represent the final part of what I am trying to solve.
Also Index 0 represent the result if nothing matches...but I could have more that one record return and process further in php

Answer 1

Assuming your where clause has the intent to always return 1 or 0 records...
simply union the index 0 always and select the top 1 descending. This will always return 1 record and it will always be the 1 matching criteria OR the 0, unless your where clause returns more than 1 record, in which case this will return the highest index matched.
SELECT Top 1 *
FROM (
SELECT *
FROM TABLE
WHERE A=A AND B=B AND C=C
UNION ALL
SELECT * FROM TABLE WHERE INDEX=0) B
ORDER BY index desc;