Making Dynamic Queries Static

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Making Dynamic Queries Static

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Leon Platt

Posted Sunday, April 28, 2002 12:00 AM

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

Post #3839

jodiem

Posted Wednesday, May 01, 2002 11:40 PM

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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

Post #32592

Robert W Marda

Posted Thursday, May 02, 2002 1:53 AM

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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
SQL Programmer
Ipreo

Post #32593

steven powell

Posted Thursday, May 02, 2002 3:47 AM

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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

Post #32594

andyj93

Posted Thursday, May 02, 2002 4:16 AM

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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

Regards,
Andy Jones

Post #32595

Lee Dise

Posted Thursday, May 02, 2002 7:20 AM

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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.

Post #32596

RyanRandall

Posted Thursday, May 02, 2002 10:20 AM

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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.

Post #32597

toddbkc

Posted Thursday, May 02, 2002 12:34 PM

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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

Post #32598

Leon Platt

Posted Monday, May 06, 2002 9:54 PM

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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='')

Post #32599

duanxn

Posted Thursday, July 11, 2002 2:23 PM

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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 "="

Post #32600

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