title: SQL Server : help removing duplicates in alternating rows
body: <pre><code>Column 0    Column 1        Column 2    Column 3    Column 4
  csus        00287y109       38          NULL        169
  mbus        01185pag4       NULL        NULL        1
  mbus        01185pag4       100         NULL        18
  mbus        018033DR8       100         NULL        5
  psus        20002309        26          NULL        5
  cbus        025816aq2       NULL        NULL        169
  cdus        02586tbj2X      101         NULL        1
  cdus        02586tbj2X      NULL        NULL        1
  </code></pre>
  
  <p>I need to remove duplicate rows from this table named combined. However not all rows are duplicated nor are the duplicate rows identical in every column. An example duplicate is row 2 and row 3. The criteria for removal is if a row exists where Column 0 and Column 1 (these are the actual column headers) are identical, keep the row which has a value in Column 2, drop the row with NULL in Column 2 if a duplicate row exists with a value in Column 0 and Column 1 and Column 2. Null values are okay as you see in Column 2, row 6 because this is not duplicated with any other row based on my criteria which focuses on the first three columns. Null is not okay if Column 0 and Column 1 are duplicated. Column 3 is always NULL and it does not matter if Column 4 is duplicated or not. The final two rows, rows 7 and 8 are also duplicated. I would want to keep row 7 because it has a value in Column 2.</p>
  
  <p><strong>Added</strong> the expected result</p>
  
  <pre><code>Column 0    Column 1        Column 2    Column 3    Column 4
  csus        00287y109       38          NULL        169
  mbus        01185pag4       100         NULL        18
  mbus        018033DR8       100         NULL        5
  psus        20002309        26          NULL        5
  cbus        025816aq2       NULL        NULL        169
  cdus        02586tbj2X      101         NULL        1
  </code></pre>
  
  <p>In the desired result Row 2 and row 8 have been removed.</p>