Query - Good practice of a query

  • Hi,

    Most of the SPs in our db written in a old format style and i dont thing that is the best way of write a query.

    eg:

    1) in where criteria

    where 1=1

    and ....

    I dont think 1=1 is necessary in where criteria. is it affect performance?

    2) all sps are written with RETURN stt. I dont think this RETURN required.

    can you also suggest some best approach/practice to write a query?

  • Even if you don't explicitly state a return value, all stored procedures have one. I prefer to do something along these lines in 2005 (similar, but different error handling, in 2000).

    CREATE MyProc

    AS

    BEGIN TRY

    ... write the query

    END TRY

    BEGIN CATCH

    ...more error handling as necessary

    RETURN ERROR_NUMBER();

    END CATCH

    RETURN 0;

    "The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
    - Theodore Roosevelt

    Author of:
    SQL Server Execution Plans
    SQL Server Query Performance Tuning

  • Balaji (1/26/2008)


    I dont think 1=1 is necessary in where criteria. is it affect performance?

    Not necessary at all. It shouldn't affect performance. The optimiser should be smart enough to ignore it. however, better be safe and take it out.

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass
  • Balaji (1/26/2008)


    1) in where criteria

    where 1=1

    and ....

    The only time I've seen this done is in generated queries. That is, a query is built from selecting various options where any combination may occur.sqlstring = "SELECT ... WHERE 1=1"

    if (opt1) then sqlstring = sqlstring + " AND (...)"

    if (opt2) then sqlstring = sqlstring + " AND (...)"

    if (op33) then sqlstring = sqlstring + " AND (...)"

    If the queries are 'hardcoded' then you may as well clean them up.

    Balaji (1/26/2008)


    can you also suggest some best approach/practice to write a query?

    Write it so it returns the right results:)

    Seriously... I've found that, although it doesn't affect performance, consistent good formatting helps keep track of what's going on. If your db has all the foreign keys defined properly, then SSMS' view creation is a good way to start; I then edit the SQL to include aliases (otherwise it's far too messy) and finallly switch to a query window to get the formatting right as the layout generated by SSMS is pretty unreadable.

    Derek.

    Derek

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