Conditional Where Clause

Hi - I am writing a C# program using SQL Server. The form I have is
collecting search criteria for a database. The main 3 fields are Category,
Type, Author.
Any combination of the 3 fields can be used. That is, All 3 fields can be
used to search on, or just 2 or just 1. If the user selects 1 or 2 fields,
I
can't use the 3rd field in the where clause of the query.
How can I create a generic query and pass a string for the "where" clause
instead of creating 7 specific queries for each possible combination of
search criteria.
Thanks,
SarahCREATE PROCEDURE getbook
@.category VARCHAR(10) = NULL,
@.bookType VARCHAR(10) = NULL,
@.author VARCHAR(10) = NULL
AS
SELECT category,
booktype,
author
FROM book
WHERE (category = @.category OR @.category IS NULL )
AND (booktype = @.bookType OR @.bookType IS NULL )
AND (author = @.author OR @.author IS NULL )|||Sarah,
From what you say is the following correct:
You want a Stored Procedure that takes 3 parameters and returns a recordset
based on the passed parameters.
The SELECT statement itself will be static, and both the first two params
will be used if present, and the third [arameter will only be used if neithe
r
of the first two params are present.
Does that sum it up?
Tony
"Sarah Sarah" wrote:

> Hi - I am writing a C# program using SQL Server. The form I have is
> collecting search criteria for a database. The main 3 fields are Category
,
> Type, Author.
> Any combination of the 3 fields can be used. That is, All 3 fields can b
e
> used to search on, or just 2 or just 1. If the user selects 1 or 2 fields
, I
> can't use the 3rd field in the where clause of the query.
> How can I create a generic query and pass a string for the "where" clause
> instead of creating 7 specific queries for each possible combination of
> search criteria.
> Thanks,
> Sarah|||Sarah,
Bearing in mind the mutual exclusivity between params 1,2 and param 3, the
following code will work:::
CREATE STORED PROCEDURE [dbo].[usp_GetSearchResults]
@.Category varchar(100)='',
@.Type varchar(100)='',
@.Author varchar(100)
AS
DECLARE @.sSQL varchar(2000)
SET @.sSQL = ''
IF @.Category ='' AND @.Type =''
BEGIN
SET @.sSQL = @.sSQL + ' SELECT Category, Type, Author '
SET @.sSQL = @.sSQL + ' FROM tblMYTABLE '
SET @.sSQL = @.sSQL + ' WHERE (@.Category='' OR Category=' + CHAR(39) +
@.Category + CHAR(39) + ') '
SET @.sSQL = @.sSQL + ' AND (@.Author ='' OR Author=' + CHAR(39) + @.Author +
CHAR(39) + ') '
END
ELSE
BEGIN
SET @.sSQL = @.sSQL + ' SELECT Category, Type, Author '
SET @.sSQL = @.sSQL + ' FROM tblMYTABLE '
SET @.sSQL = @.sSQL + ' WHERE (@.Category='' OR Category=' + CHAR(39) +
@.Category + CHAR(39) + ') '
SET @.sSQL = @.sSQL + ' AND (@.Type ='' OR Type=' + CHAR(39) + @.Type +
CHAR(39) + ') '
END
EXEC (@.sSQL)
You do not necessarily need the character string to create the select
statement, it does help with debugging though.
Hope it helps,
Tony
"Sarah Sarah" wrote:

> Hi - I am writing a C# program using SQL Server. The form I have is
> collecting search criteria for a database. The main 3 fields are Category
,
> Type, Author.
> Any combination of the 3 fields can be used. That is, All 3 fields can b
e
> used to search on, or just 2 or just 1. If the user selects 1 or 2 fields
, I
> can't use the 3rd field in the where clause of the query.
> How can I create a generic query and pass a string for the "where" clause
> instead of creating 7 specific queries for each possible combination of
> search criteria.
> Thanks,
> Sarah|||KenJ - thanks - this logic will work, but I am getting a syntax error:
"Duplicated parameter names are not allowed"
when I try to do this in Query builder. Any idea what would cause this erro
r.
Thanks,
Sarah
"KenJ" wrote:

> CREATE PROCEDURE getbook
> @.category VARCHAR(10) = NULL,
> @.bookType VARCHAR(10) = NULL,
> @.author VARCHAR(10) = NULL
> AS
> SELECT category,
> booktype,
> author
> FROM book
> WHERE (category = @.category OR @.category IS NULL )
> AND (booktype = @.bookType OR @.bookType IS NULL )
> AND (author = @.author OR @.author IS NULL )
>|||I'm not familiar with query builder. Can you run it in query analyzer?
Here is a sample script that creates a table, loads some dummy data,
runs the procedure with several variations then drops the table and
procedure. I've run it in query analyzer to be sure it works...
USE tempdb
GO
SET nocount ON
GO
CREATE TABLE book (
bookid INT IDENTITY( 1 , 1 ) NOT NULL PRIMARY KEY
, category VARCHAR(10) NULL
, booktype VARCHAR(10) NULL
, author VARCHAR(10) NULL)
GO
INSERT book
VALUES('fiction'
, 'paperback'
, 'twain')
INSERT book
VALUES('fiction'
, 'hardbound'
, 'asimov')
INSERT book
VALUES('fiction'
, 'paperback'
, 'rand')
GO
CREATE PROCEDURE getbook
@.category VARCHAR(10) = NULL
, @.bookType VARCHAR(10) = NULL
, @.author VARCHAR(10) = NULL
AS
SELECT category
, booktype
, author
FROM book
WHERE (category = @.category
OR @.category IS NULL )
AND (booktype = @.bookType
OR @.bookType IS NULL )
AND (author = @.author
OR @.author IS NULL )
GO
-- get all fiction books
EXEC getbook @.category = 'fiction'
-- all fiction books by rand
EXEC getbook @.category = 'fiction' ,
@.author = 'rand'
-- all paperbacks
EXEC getbook @.bookType = 'paperback'
-- returns all books since we don't supply any filter
EXEC getbook
GO
DROP TABLE book
GO
DROP PROCEDURE getbook
GO|||On Wed, 1 Feb 2006 16:50:27 -0800, Sarah Sarah wrote:

>Hi - I am writing a C# program using SQL Server. The form I have is
>collecting search criteria for a database. The main 3 fields are Category,
>Type, Author.
>Any combination of the 3 fields can be used. That is, All 3 fields can be
>used to search on, or just 2 or just 1. If the user selects 1 or 2 fields,
I
>can't use the 3rd field in the where clause of the query.
>How can I create a generic query and pass a string for the "where" clause
>instead of creating 7 specific queries for each possible combination of
>search criteria.
Hi Sarah,
Many ways to skin this cat can be found i Erland Sommarskog's article:
http://www.sommarskog.se/dyn-search.html
Hugo Kornelis, SQL Server MVP|||Please post DDL, so that people do not have to guess what the keys,
constraints, Declarative Referential Integrity, data types, etc. in
your schema are. Sample data is also a good idea, along with clear
specifications. It is very hard to debug code when you do not let us
see it.
It would also help if you would learn that a field and a column nothing
whatsoever alike and that names like "type", "category", etc. are too
vague to be data element names/. Try something like this:
CREATE PROCEDURE GetBook
(@.my_book_category VARCHAR(10) = NULL, -- wild guess
@.my_book_type INTEGER = NULL, -- Dewey Decimal ?
@.my_author_name VARCHAR(25) = NULL)
AS
SELECT book_category, book_type, author_name
FROM Library
WHERE book_category = COALESCE (@.my_book_category, book_category)
AND book_type = COALESCE (@.my_book_type, book_type)
AND author_name = COALESCE (@.my_author_name, author_)name) ;|||> WHERE book_category = COALESCE (@.my_book_category, book_category)
> AND book_type = COALESCE (@.my_book_type, book_type)
> AND author_name = COALESCE (@.my_author_name, author_)name) ;
That would give a tablescan.
Can you imagine how badly that will perform on a table with a few million
rows perhaps 1GB in size.
To do the tablescan everytime a user ran the query SQL Server would have to
read 1GB of data.
Now, multiply that by 10 users, thats 10GB of data SQL Server now needs to
read in order to process all 10 queries.
You are going to need one hell of a big box!
The correct way to do this is to either use IF..ELSE to make the query more
specific depending on which parameters are specified, ie. only put the
parameters specified on the WHERE clause.
Tony Rogerson
SQL Server MVP
http://sqlserverfaq.com - free video tutorials
"--CELKO--" <jcelko212@.earthlink.net> wrote in message
news:1138944895.900338.14850@.g47g2000cwa.googlegroups.com...
> Please post DDL, so that people do not have to guess what the keys,
> constraints, Declarative Referential Integrity, data types, etc. in
> your schema are. Sample data is also a good idea, along with clear
> specifications. It is very hard to debug code when you do not let us
> see it.
> It would also help if you would learn that a field and a column nothing
> whatsoever alike and that names like "type", "category", etc. are too
> vague to be data element names/. Try something like this:
> CREATE PROCEDURE GetBook
> (@.my_book_category VARCHAR(10) = NULL, -- wild guess
> @.my_book_type INTEGER = NULL, -- Dewey Decimal ?
> @.my_author_name VARCHAR(25) = NULL)
> AS
> SELECT book_category, book_type, author_name
> FROM Library
> WHERE book_category = COALESCE (@.my_book_category, book_category)
> AND book_type = COALESCE (@.my_book_type, book_type)
> AND author_name = COALESCE (@.my_author_name, author_)name) ;
>|||Don't forget Ken that the query below will give you a very general plan so
you'll probably end up doing a table scan.
Check the plan before you decided on the solution.
Much better to use IF ELSE or dynamic SQL and taylor your query to the
parameters passed.
Tony.
Tony Rogerson
SQL Server MVP
http://sqlserverfaq.com - free video tutorials
"KenJ" <kenjohnson@.hotmail.com> wrote in message
news:1138899994.839100.3010@.o13g2000cwo.googlegroups.com...
> I'm not familiar with query builder. Can you run it in query analyzer?
> Here is a sample script that creates a table, loads some dummy data,
> runs the procedure with several variations then drops the table and
> procedure. I've run it in query analyzer to be sure it works...
> USE tempdb
> GO
> SET nocount ON
> GO
> CREATE TABLE book (
> bookid INT IDENTITY( 1 , 1 ) NOT NULL PRIMARY KEY
> , category VARCHAR(10) NULL
> , booktype VARCHAR(10) NULL
> , author VARCHAR(10) NULL)
> GO
> INSERT book
> VALUES('fiction'
> , 'paperback'
> , 'twain')
> INSERT book
> VALUES('fiction'
> , 'hardbound'
> , 'asimov')
> INSERT book
> VALUES('fiction'
> , 'paperback'
> , 'rand')
> GO
> CREATE PROCEDURE getbook
> @.category VARCHAR(10) = NULL
> , @.bookType VARCHAR(10) = NULL
> , @.author VARCHAR(10) = NULL
> AS
> SELECT category
> , booktype
> , author
> FROM book
> WHERE (category = @.category
> OR @.category IS NULL )
> AND (booktype = @.bookType
> OR @.bookType IS NULL )
> AND (author = @.author
> OR @.author IS NULL )
> GO
> -- get all fiction books
> EXEC getbook @.category = 'fiction'
> -- all fiction books by rand
> EXEC getbook @.category = 'fiction' ,
> @.author = 'rand'
> -- all paperbacks
> EXEC getbook @.bookType = 'paperback'
> -- returns all books since we don't supply any filter
> EXEC getbook
> GO
> DROP TABLE book
> GO
> DROP PROCEDURE getbook
> GO
>