Performance in Inner Join on VBAK

Question

HI,
For a customized report the select statement was written like this which is giving time out error for large data. How one can improve performance of following Inner Joins.
  SELECT  *
      INTO CORRESPONDING FIELDS OF TABLE it_tab
       FROM vbak as A INNER JOIN vbuk as B
              ON Avbeln = Bvbeln
            INNER JOIN vbkd as C
             ON Avbeln = Cvbeln
  WHERE    A~vbeln      IN  so_vbeln
     AND   A~audat      IN  so_audat
     AND   A~auart      IN  so_auart
     AND   A~augru      IN  so_augru
     AND   A~faksk    IN  so_faksp
     AND   A~vkorg      IN  so_vkorg
     AND   A~vtweg      IN  so_vtweg
     AND   A~spart      IN  so_spart
     AND   A~vkbur      IN  so_vkbur
     AND   A~vkgrp      IN  so_vkgrp
     AND   A~vsbed      IN  so_vsbed
     AND   A~kunnr      IN  so_kunnr
     and   B~gbstk      IN  so_gbstx
     AND   C~posnr       =  '000000'.
Thanks
anya
Moderator message: FAQ, it all depends on the content of the so_ ranges at runtime.
Please Read before Posting in the Performance and Tuning Forum
Edited by: Thomas Zloch on Nov 1, 2010 11:57 AM

Answer 1

Others have already responded, and I would only like to dwell on the answers for a short while. Or maybe rather the question.
This question is typical for the inexperienced developer. This particular question is actually a little different, because there is a straight answer: there is no difference. For most questions of this type the answer is "it depends", because one
particular syntax can happen to perform better with one set of data and indexes, but with a different data/index profile another syntax gives better result.
Ideally, as long as two queries are logically equivalent, the syntax should not matter at all, because the optimizer should always figure out the best way to achieve the result. In practice, this is not the case, because there are lots of limitaitons in
an optimizer in an RDBMS.
While it certainly can matter for performance how you write your queries, that is not what you should focus on. What you should focus is to express your query as clearly as possible, and make sure that you have the relevant indexes in place. There is one
rule when it comes to query-writing you should take your heart: never entable a column in a condition in an expression, because that is likely to render index on that column useless.
For this particular question, the answer is that as you long as you write code for SQL Server, use the JOIN syntax. But if you use that in the Oracle world, you may get funny looks from people. It's a different culture over there...
Erland Sommarskog, SQL Server MVP, [email protected]