Making Dynamic Queries Static

  • Leon Platt

    SSCommitted

    Points: 1921

    Comments posted to this topic are about the content posted at http://www.sqlservercentral.com/columnists/lplatt/makingdynamicqueriesstatic.asp

  • jodiem

    SSC Veteran

    Points: 254

    Thanks for the article, it is very useful.

    I would love to see your > solution and can I ask for a between solution also.

    This is the query that I'm trying to do at the moment:

    I need a query that does both And's or Ors and works on multiple tables. Eg the query is about house features The Square foot is stored in one table The rooms are stored in another table The features are stored in another table again (Similar to your scenario in your article).

    The user wants to query a house that is between 2000 and 3000 square foot, with 3 bathrooms (from the rooms table) and with the following features eg porch, fireplace (each stored as a record in the features table)

    That was the simplified version, I would love to be able to expand it to query other things that we store about the houses.

    Jodie

  • Robert W Marda

    SSChampion

    Points: 13413

    One way to modify solution 2 to work with the mentioned operators (=, <>, > , <, IN) is to create the WHERE clause like this:

    WHERE (A.name = @Aname or @Aname = '') and (C.firstName like @Cfirst or @Cfirst = '') and (C.lastName like @Clast or @Clast = '') and (D.city like @city or @city = '') and (D.state = @state or D.state = '') and (D.phone like @phone or @phone = '')

    This solution removes the assumption that a NULL record is included. It also means that if you do not want to limit the result set by a city name simply send in @city = '' and that part of the WHERE clause will be completely ignored. It will just limit the result set on all other parameters that are not equal to ''.

    Robert Marda

    Robert W. Marda
    Billing and OSS Specialist - SQL Programmer
    MCL Systems

  • steven powell

    Mr or Mrs. 500

    Points: 557

    here's one way to solve the problem posed by soln. number two

    and isnull(ColumnOne, '%') like @pSearchArg

    to use other operators (=, > etc.) try something like

    and ColumnOne = insnull(@pSearchArg, ColumnOne)

    the optimiser can still use an index on ColumnOne if there is one

  • Andy Jones, DBA

    Hall of Fame

    Points: 3641

    Hi, how about :-

    SELECT

    *

    from

    account A

    inner Join Contact C on a.primarykey=c.accountkey

    inner join Address D on A.primarykey=D.foreignkey

    WHERE

    case

    when @Aname is null then A.Name

    else @Aname

    end = A.Name

    and

    case

    when @Cfirst is null then C.firstName

    else @Cfirst

    end = C.firstName

    and

    case

    when @Clast is null then C.lastName

    else @Clast

    end = C.lastName

    and

    case

    when @city is null then D.city

    else @city

    end = D.city

    and

    case

    when @state is null then D.state

    else @state

    end = D.state

    and

    case

    when @phone is null then D.phone

    else @phone

    end = D.phone

    Andy

    andyj93@hotmail.com

    .

  • Lee Dise

    SSCarpal Tunnel

    Points: 4384

    The only time you absolutely need to use dynamic SQL is when, at compile time, you do not know the names of the database or the database objects against which your query will execute.

    WHERE criteria do not count: As the author pointed out, there are ways to construct a WHERE clause to go this way or that depending upon whether a parameter value is missing.

    It's the FROM clause that makes dynamic SQL essential. If, for example, I wish to write a procedure that performs a query against system tables, and I want at run time to specify which database I'm querying. The only way to turn the database name into a variable is through dynamic SQL. Or if your database contains two or more tables having the same or similar structure, and again you won't know until run-time which tables are to be queried... this is a job for dynamic SQL.

  • RyanRandall

    SSChampion

    Points: 13623

    I guess you could change your FROM situation to a WHERE situation by creating a view of the union of your similar tables (together with a flag to indicate where they're from).

    This would, of course, have other implications.

    Ryan Randall

    Solutions are easy. Understanding the problem, now, that's the hard part.

  • toddbkc

    SSC Veteran

    Points: 254

    I have had good luck using the OR statement instead of LIKE. Often, I find that the LIKE statement doesn't always like to read the index.

    So, when I do this, the statement looks like:

    select * from table1

    where (@first_name IS NULL or first_name = @first_name)

    and (@last_name IS NULL or last_name = @last_name) etc...

    I've found really great performance overall in the majority of cases. Of course, this doesn't handle if you really wanted the LIKE statement, but often I am looking for an exact match.

    Todd


    Todd

  • Leon Platt

    SSCommitted

    Points: 1921

    Thanks; everyone for the responses to my article. I will try to address everyone in the next day or two. Lets start with spowell_2 because your solution is basically the same as mine was. My solution was:

    isnull(Column, ' ') like @Parameter.

    Unfortunately you take a little hit with cpu time to do the isnull function on each column but its a very clean solution.

    tbredehoft - what do you do with the parameters where the user does not enter any search critera? You end up with a situation like where (firstName is null or firstname='')

  • duanxn

    SSC Enthusiast

    Points: 110

    Hi, I think

    ColumnOne = insnull(@pSearchArg, ColumnOne)

    whill not work, because null value in ColumnOne will fail this expression.

    I'd like to use something like the following if you insist on using "like":

    CREATE PROCEDURE sp_MySearch

    @p1 varchar(50),

    @p2 varchar(50),

    AS

    select * from t where

    isnull(c1, '') like case when len(isnull(@p1,'')) =0 then isnull(c1, '') else '%'+@p1+'%' end and

    isnull(c2, '') like case when len(isnull(@p2,'')) =0 then isnull(c2, '') else '%'+@p2+'%' end

    Of cause the performance using "like" is far poor than using a "="

  • duanxn

    SSC Enthusiast

    Points: 110

    Sorry, I should use this instead of my last post:

    CREATE PROCEDURE sp_MySearch

    @p1 varchar(50),

    @p2 varchar(50)

    As

    select * from t

    where

    isnull(c1, isnull(@p1,'')) like case when len(isnull(@p1,'')) =0 then isnull(c1, '') else '%'+@p1+'%' end and

    isnull(c2, isnull(@p2,'')) like case when len(isnull(@p2,'')) =0 then isnull(c2, '') else '%'+@p2+'%' end

  • Mohammad Fayaz

    Grasshopper

    Points: 21

    Hi Leon,

    Great article. I thnk even this solution would work:

     

    IsNull(state,'') like IsNull(@State,'')

    Or

    state like IsNull(@state,state)+''

    I am using this in a procedure and it seems to work fine.

     

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