Database

26-Mar-05 5:57

Suppose i create sp

CREATE PROC myProc @criteria1 int,
@criteria2 nvarchar(50) = ''

AS

SELECT * FROM myTable

WHERE column1 = @criteria1
AND
column2 = @criteria2
GO

---------------------------

my question is in case the parameter @criteria2 is empty (equal '')
i want the select will ignore this criteria
so it perform like:

SELECT * FROM myTable

WHERE column1 = @criteria1

-----
the same with other criterias.
I can have a lot of parameters and and some of them can be empty or not.
Thanks.

------------------------------------
To study, study and only to study

turbochimp26-Mar-05 11:35

turbochimp

26-Mar-05 11:35

You can use conditional logic in your procedure, but you may want to consider why you've got empty parameters coming into a stored procedure - there are valid reasons, but it's nice to try to avoid it. You can also set defaults on parameters to sidestep having to use conditional logic in some cases.

Example:

-- These variables would typically be input params<br />
declare @param1 nvarchar(10)<br />
declare @param2 nvarchar(10)<br />
set @param2 = 'Value1'<br />
<br />
-- These variables just hold the length of the params<br />
declare @lenP1 int<br />
declare @lenP2 int<br />
set @lenP1 = len(@param1)<br />
set @lenP2 = len(@param2)<br />
<br />
-- Outputs the state of the params<br />
if @lenP1 > 0 and @lenP2 > 0<br />
	select 'Both parameters were provided.'<br />
else if @lenP1 > 0 and (@lenP2 = 0 or @lenP2 is null)<br />
	select 'The first parameter was provided but the second was omitted'<br />
else<br />
        -- This statement will be executed.<br />
	select 'The second parameter was provided but the first was omitted'

The most exciting phrase to hear in science, the one that heralds the most discoveries, is not 'Eureka!' ('I found it!') but 'That's funny...’

Colin Angus Mackay29-Mar-05 1:03

29-Mar-05 1:03

Instead of defaulting the value to an empty string you can leave it as null

Then you can do a select like this

CREATE PROCEDURE MyProcedure
@criteria1 int,
@criteria2 varchar(50)
AS

SELECT *
FROM MyTable
WHERE column1 = @criteria1
AND (@criteria2 IS NULL OR column2 = @criteria2)
GO

The key here is the AND... line. What it says is that if @criteria2 is null then the clause is true. If @criteria2 is not null then column2 must equal @criteria2 for the clause to be true. In an OR condition one or both sides must be true for the whole to be true.

Does this help?

My: Blog | Photos | Next SQL Presentation
WDevs.com - Open Source Code Hosting, Blogs, FTP, Mail and More

_J_29-Mar-05 1:41

29-Mar-05 1:41

Yes, thanks it's help. However the statement that u wrote:

AND (@criteria2 IS NULL OR column2 = @criteria2)

possible write as:

WHERE column1 = @criteria1
AND (column2 = ISNULL(@criteria2, column2))

------------------------------------
To study, study and only to study

Colin Angus Mackay29-Mar-05 1:48

29-Mar-05 1:48

If you want you can write it that way too. However, I'd think that using a function like this wouldn't be as efficient (but SQL Server often surprises me with what it can do efficiently and what not) - so, if that is important to you then you should consider writing both versions and running them through the query analyser to see which generates the better execution plan.

My: Blog | Photos | Next SQL Presentation
WDevs.com - Open Source Code Hosting, Blogs, FTP, Mail and More

_J_29-Mar-05 1:51

29-Mar-05 1:51

generates the better execution plan, what do u mean by saying it?
how to check execution plan in the query analyser.

Thank u

------------------------------------
To study, study and only to study

Colin Angus Mackay29-Mar-05 1:56

29-Mar-05 1:56

Query-->Show Execution Plan. Or Press Ctrl+K

Then run the query. The plan that the query optimiser used will be shown after the query is run. You can examine it to see which is more efficient.

My: Blog | Photos | Next SQL Presentation
WDevs.com - Open Source Code Hosting, Blogs, FTP, Mail and More

_J_29-Mar-05 2:02

Saving file in SQL Server

29-Mar-05 2:02

thanks i got it,

I have another question to u: i have stored procedure that perform select ... from ....
also this procedure return value (e.g. return 0)

if i call to the sp by EXECUTE i got the result of my sp(result of query.)

if i do:
DECLARE @res int

EXEC @res = My Stored proc
PRINT @res

i got only what the sp return.

how to get the return value and the query result(set result) both?

------------------------------------
To study, study and only to study

dabuskol25-Mar-05 19:48

dabuskol

25-Mar-05 19:48

Hi Guys,

Please give advice.
I have a program that attached files. What I do is after pressing the save button it saves the entire path of the file to my table plus of course the key (attach with columns userid,fileloc,filename) regarding the physical file I saved it in a pre defined directory in our server which is related to my WEB PAGE PROJECT.

Question: What is the advantage of saving the entire file into a SQL Server rather than what i've mentined above?

/Dabuskol

Re: Saving file in SQL Server

turbochimp25-Mar-05 20:12

turbochimp

25-Mar-05 20:12

That's kind of a hard question to answer without any other context. It seems like, if you have to ask what the advantages are, it's probably not something you really need to worry about just yet.

I guess there are obvious differences, but it's hard to say if they're advantages without knowing what it is you're trying to accomplish.

If the application may be sold to others, or there are potential file system sharing issues (networked users may need access to files), then saving the files to the database may be an advantage.

If file versioning is something you want to implement, databases offer some advantages over the file system alone.

Backups may be arguably simpler (or at least require less third-party software in many cases).

There are potential security advantages in storing files in a database - it's almost impossible to execute a malicious script if it's stored in a BLOB...

There are no doubt other, more situation-specific advantages to storing files in a database versus the file system, but there are also potential disadvantages.

Accessing a file stored in a database is seldom as fast as accessing one from the file system.
Sharing copies of a file stored in a database certainly takes more steps than sharing one on the file system.
Storing files of any size in a database can cause significant bloat, etc.

Good luck.

The most exciting phrase to hear in science, the one that heralds the most discoveries, is not 'Eureka!' ('I found it!') but 'That's funny...’

SELECT TOP

vuthaianh25-Mar-05 12:10

vuthaianh

25-Mar-05 12:10

CREATE PROCEDURE proname
@param int,

AS
SELECT TOP @param field1, field2, fiedl3
FROM tablename
GO

When executing the stored procedure i above, i'm reported that error happens at @param
How could i pass parameter in 'SELECT TOP' statement above
Thanks

Re: SELECT TOP

turbochimp25-Mar-05 17:49

turbochimp

25-Mar-05 17:49

You aren't allowed to use a parameter with TOP in that way.

You could, however, concatenate a sql expression using the parameter, like:

declare @param int<br />
declare @sql nvarchar(100)<br />
set @param = 10<br />
<br />
set @sql = 'select top ' + cast(@param as nvarchar(4)) + ' * from FooTable'<br />
<br />
exec (@sql)

Does that help?

The most exciting phrase to hear in science, the one that heralds the most discoveries, is not 'Eureka!' ('I found it!') but 'That's funny...’

Simplify a T-SQL

WDI25-Mar-05 7:41

WDI

25-Mar-05 7:41

How i can simplify this statement to better performance?
T is a table .
Column ID is not unique.

SELECT DISTINCT ID FROM T

WHERE
ID IN (SELECT ID FROM T WHERE TypeID = i)
and ID IN (SELECT ID FROM T WHERE TypeID = j)
.
.
.
and ID IN (SELECT ID FROM T WHERE TypeID = k)

and ID NOT IN (SELECT ID FROM T WHERE TypeID NOT IN (i , j , ... , k ) )

Michael Potter25-Mar-05 8:24

Michael Potter

25-Mar-05 8:24

If you are looking for all IDs that have a record with a TypeID of i and j and k and at least one other TypeID then I think this would work:

SELECT
    DISTINCT a.ID
FROM
    T AS a
INNER JOIN 
    T AS b
    ON (a.ID = b.ID)
INNER JOIN
    T AS c
    ON (a.ID = c.ID)
INNER JOIN
    T AS d
    ON (a.ID = d.ID)
WHERE
    a.TypeID = i,
    b.TypeID = j,
    c.TypeID = k,
    d.TypeId NOT IN (i,j,k)

WDI25-Mar-05 9:10

WDI

25-Mar-05 9:10

There is an error in your statement.

Are u sure this statement has a better performance?

Any Idea?

Michael Potter25-Mar-05 11:34

Michael Potter

25-Mar-05 11:34

The error might be in the engine - I use MS SQL 2000 - or it may be that there is typo since I didn't create any test tables.

Only examining the execution plan between the two queries and testing will tell you which one is faster. Indexes also help.

My experience is that IN (or NOT IN) statments tend to generate more table scans whereas JOIN makes use of indexes better. Given your set of criteria, an index on [TypeID, ID] could generate a faster query.

Tony Lewis25-Mar-05 9:41

Tony Lewis

25-Mar-05 9:41

Try this:

select ID from
(Select ID, sum(case when TypeID in ('I', 'J', 'K', 'L', 'M') then 1 else 0 end) as InList,
sum(case when TypeID in ('I', 'J', 'K', 'L', 'M') then 0 else 1 end) as NotInList
from t
group by ID) as foo
where inlist > 0 and NotInList = 0

Tony Lewis
SQL "Guru"
XAKTsoft, Inc.

andyharman28-Mar-05 4:32

andyharman

28-Mar-05 4:32

I used the following method a few years back:

SELECT ID FROM T
WHERE TypeId IN (i, j, k)
GROUP BY ID
HAVING COUNT(DISTINCT TypeId) = 3

Where "3" is the number of terms in the "IN" clause. To handle your "NOT IN" requirement, you could use the following:

SELECT ID FROM T
WHERE ID IN (SELECT ID FROM T
    WHERE TypeId IN (i, j, k)
    GROUP BY ID
    HAVING COUNT(DISTINCT TypeId) = 3)
GROUP BY ID
HAVING COUNT(DISTINCT TypeId) = 3

I don't know how fast this will run against your chosen database engine. Under SQL-Server, I would normally expect the following indexes to help:

Clustered index on T (ID, TypeId)

And possibly:

Nonclustered index on T (TypeId)

Hope this helps.

Regards
Andy

DateTime

vuthaianh25-Mar-05 5:24

vuthaianh

25-Mar-05 5:24

i just want to save time in a field got type is datetime, but every time i insert time into the field, SQL SERVER automatically add day to that field.
Any way to solve this problem? Thanks in advance

Re: DateTime

Colin Angus Mackay25-Mar-05 6:29