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Editorial Team
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Asked: 2026-05-28T14:10:06+00:00

To retrieve values which are not in db, I use Common Table Expression like

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To retrieve values which are not in db, I use Common Table Expression like this :

;WITH new_id (id) AS (
  SELECT '0x01'
  UNION ALL SELECT '0x00'
  UNION ALL SELECT '0x03'
  UNION ALL SELECT '0x04'
  UNION ALL SELECT '0x05'
)

SELECT  id AS p
FROM   new_id ni EXCEPT(SELECT id FROM table)

Is this an optimized way to retrieve values which are not stored in DB ?

Kind regards,

Florian

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1 Answer

  1. Editorial Team

    That should be fine.

    For a large number of rows (especially if they contain long string values) I have noticed that these internal tables of constants can take a long time to compile but I doubt you will hit this issue for 30 rows.

    From a quick test this end they have an advantage over table variables as SQL Server seems to maintain some statistical information about them so can choose an appropriate join type.

    I just tried a CTE with 500 rows and 50 distinct values and the estimated number of rows in the plan below was correct. (though it is a bit of a shame that having worked all this stuff out at compile time and presumably having generated a distinct list of ids for that purpose that SQL Server doesn’t just substitute that into the plan instead of having to do it again at run time)

    Plan

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