From: esquel@sommarskog.se   
      
   Phil Hunt (aaa@aaa.com) writes:   
   > In the studio query design, I can join any tables up. Now I understand   
   > Inner Join is associative. But if there is an Outer join in the mix, how   
   > does the studio determine the order of the joint ?   
      
   I don't know. And the reason I don't know is because I never use the   
   Query Designer. And I can't really recommend usage of it. There are   
   just too many SQL constructs it does not support.   
      
   On the other hand, I do know the difference between LEFT and RIGHT JOIN.   
   Well, tney are not very different. These two queries are equal:   
      
   SELECT a.col1, b.col2   
   FROM   a   
   LEFT   JOIN b ON a.col0 = b.col0   
      
   SELECT a.col1, b.col2   
   FROM   b   
   RIGHT  JOIN a ON a.col0 = b.col0   
      
   Both queries will return all rows in table a. For the rows where there is no   
   matching row in b, the value of b.col2 will be NULL.   
      
   So when do you use LEFT JOIN and when do you use RIGHT JOIN? The answer   
   is that you always use LEFT JOIN and never RIGHT JOIN. At least that is   
   what I do. RIGHT JOIN gives me headache, because everything is   
   backwards.   
      
   The simple rule is: in a LFFT JOIN all rows in the table on the left side   
   are retained, while the table on the right side is filtered by the ON   
   clause.   
      
      
      
   --   
   Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se   
      
   Links for SQL Server Books Online:   
   SQL 2008: http://msdn.microsoft.com/en-us/sqlserver/cc514207.aspx   
   SQL 2005: http://msdn.microsoft.com/en-us/sqlserver/bb895970.aspx   
      
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