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  • What are the advantages of a query using a derived table(s) over a query not using them?

    - by AspOnMyNet
    I know how derived tables are used, but I still can’t really see any real advantages of using them. For example, in the following article http://techahead.wordpress.com/2007/10/01/sql-derived-tables/ the author tried to show benefits of a query using derived table over a query without one with an example, where we want to generate a report that shows off the total number of orders each customer placed in 1996, and we want this result set to include all customers, including those that didn’t place any orders that year and those that have never placed any orders at all( he’s using Northwind database ). But when I compare the two queries, I fail to see any advantages of a query using a derived table ( if nothing else, use of a derived table doesn't appear to simplify our code, at least not in this example): Regular query: SELECT C.CustomerID, C.CompanyName, COUNT(O.OrderID) AS TotalOrders FROM Customers C LEFT OUTER JOIN Orders O ON C.CustomerID = O.CustomerID AND YEAR(O.OrderDate) = 1996 GROUP BY C.CustomerID, C.CompanyName Query using a derived table: SELECT C.CustomerID, C.CompanyName, COUNT(dOrders.OrderID) AS TotalOrders FROM Customers C LEFT OUTER JOIN (SELECT * FROM Orders WHERE YEAR(Orders.OrderDate) = 1996) AS dOrders ON C.CustomerID = dOrders.CustomerID GROUP BY C.CustomerID, C.CompanyName Perhaps this just wasn’t a good example, so could you show me an example where benefits of derived table are more obvious? thanx

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  • Join Where Rows Don't Exist or Where Criteria Matches...?

    - by Greg
    I'm trying to write a query to tell me which orders have valid promocodes. Promocodes are only valid between certain dates and optionally certain packages. I'm having trouble even explaining how this works (see psudo-ish code below) but basically if there are packages associated with a promocode then the order has to have one of those packages and be within a valid date range otherwise it just has to be in a valid date range. The whole "if PrmoPackage rows exist" thing is really throwing me off and I feel like I should be able to do this without a whole bunch of Unions. (I'm not even sure if that would make it easier at this point...) Anybody have any ideas for the query? if `OrderPromoCode` = `PromoCode` then if `OrderTimestamp` is between `PromoStartTimestamp` and `PromoEndTimestamp` then if `PromoCode` has packages associated with it //yes then if `PackageID` is one of the specified packages //yes code is valid //no invalid //no code is valid Order: OrderID* | OrderTimestamp | PackageID | OrderPromoCode 1 | 1/2/11 | 1 | ABC 2 | 1/3/11 | 2 | ABC 3 | 3/2/11 | 2 | DEF 4 | 4/2/11 | 3 | GHI Promo: PromoCode* | PromoStartTimestamp* | PromoEndTimestamp* ABC | 1/1/11 | 2/1/11 ABC | 3/1/11 | 4/1/11 DEF | 1/1/11 | 1/11/13 GHI | 1/1/11 | 1/11/13 PromoPackage: PromoCode* | PromoStartTimestamp* | PromoEndTimestamp* | PackageID* ABC | 1/1/11 | 2/1/11 | 1 ABC | 1/1/11 | 2/1/11 | 3 GHI | 1/1/11 | 1/11/13 | 1 Desired Result: OrderID | IsPromoCodeValid 1 | 1 2 | 0 3 | 1 4 | 0

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  • SQL Server unique constraint problem

    - by b0x0rz
    How to create a unique constraint on a varchar(max) field in visual studio, visually. the problem is when i try it: manage indexes and keys add columns I can only chose the bigint columns, but not any of the varchar(max) ones. Do I maybe have to use check constraints? If yes, what to put in the expression? Thnx for the info

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  • How to lock a table for inserting in sql?

    - by Nandini
    hi, i have a web application in which i have a page named 'Data'.Many people will try to insert data into the table at a given time.So the reference no other than the primary key will get duplicated which should not be permitted.For inserting the data into the DB table, i am using a stored procedure in SQL.In my vb.net web application, i am using Business layer with enterprise library for calling the stored procedure.Now i want to lock the table for inserting so that when multiple user inserts, there wont be any complication.How can i do this?Please advice Regards

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  • Where to put conditionals in ANSI-syntax SQL queries

    - by RenderIn
    What's the difference between these two queries? I've been resistant to jumping on the ANSI-syntax bandwagon because I have not been able to unravel various syntactical ambiguities. Is 1) returning the product of the join and only then filtering out those joined records which have weight = 500? And is 2) filtering out those prior to the join? Is 2 bad syntax? Why might I use that? 1: SELECT SOMETHING FROM FOO INNER JOIN BAR ON FOO.NAME = BAR.NAME WHERE BAR.WEIGHT < 500 2: SELECT SOMETHING FROM FOO INNER JOIN BAR ON FOO.NAME = BAR.NAME AND BAR.WEIGHT < 500

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  • SQL Server unique contraint problem

    - by b0x0rz
    How to create a unique constraint on a varchar(max) field in visual studio, visually. the problem is when i try it: manage indexes and keys add columns i can only chose the bigint columns, but not any of the varchar(max) ones. do i maybe have to use check constraints? if yes, what to put in the expression? thnx for the info

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  • how to save byte[] value to varbinary(64) field on database

    - by shamim
    byte[] a = HashEncript("a"); public byte[] HashEncript(string Password) { SHA512Managed sha = new SHA512Managed(); byte[] hash = sha.ComputeHash(UnicodeEncoding.Unicode.GetBytes(Password)); return hash; } i want to save byte[] a this value on my database .My database field is varbinary(64).i use msSQL2008 .how to save ,want to know the insert query with C# code.

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  • Is it OK to re-create many SQL connections (SQL 2008)

    - by Mr. Flibble
    When performing many inserts into a database I would usually have code like this: using (var connection = new SqlConnection(connStr)) { connection.Open(); foreach (var item in items) { var cmd = new SqlCommand("INSERT ...") cmd.ExecuteNonQuery(); } } I now want to shard the database and therefore need to choose the connection string based on the item being inserted. This would make my code run more like this foreach (var item in items) { connStr = GetConnectionString(item); using (var connection = new SqlConnection(connStr)) { connection.Open(); var cmd = new SqlCommand("INSERT ...") cmd.ExecuteNonQuery(); } } Which basically means it's creating a new connection to the database for each item. Will this work or will recreating connections for each insert cause terrible overhead?

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  • How much Stored Procedures created everyday ?

    - by Space Cracker
    I make a query that return to me the count of Stored Procedure that created everyday as follow SELECT convert(varchar, crdate, 103) as Date,Count(*) as Counter FROM sysobjects WHERE (xtype = 'p') AND (name NOT LIKE 'dt%') Group by convert(varchar, crdate, 103) and its already work but dates appear in string format that i can't order it such as below 01/03/2010 3 01/04/2008 4 01/05/2010 5 01/11/2008 1 01/12/2008 4 02/03/2008 1 02/03/2010 2 02/04/2008 4 02/05/2010 2 02/11/2008 2 02/11/2009 2 02/12/2008 4 03/01/2010 1 03/02/2010 2 03/03/2010 2 03/04/2008 2 03/04/2010 2 03/05/2008 1 03/05/2010 2 I want to make that in which date is in datetime format that i can make order by successfully, i tried convert(datetime, crdate, 103) but it show Full date any idea of how to do ?

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  • Using "CASE" in Where clause to choose various column harm the performance

    - by zivgabo
    I have query which needs to be dynamic on some of the columns, meaning I get a parameter and according its value I decide which column to fetch in my Where clause. I've implemented this request using "CASE" expression: (CASE @isArrivalTime WHEN 1 THEN ArrivalTime ELSE PickedupTime END) >= DATEADD(mi, -@TZOffsetInMins, @sTime) AND (CASE @isArrivalTime WHEN 1 THEN ArrivalTime ELSE PickedupTime END) < DATEADD(mi, -@TZOffsetInMins, @fTime) If @isArrivalTime = 1 then chose ArrivalTime column else chose PickedupTime column. I have a clustered index on ArrivalTime and nonclustered index on PickedupTime. I've noticed that when I'm using this query (with @isArrivalTime = 1), my performance is a lot worse comparing to only using ArrivalTime. Maybe the query optimizer can't use\choose the index properly in this way? I compared the execution plans an noticed that when I'm using the CASE 32% of the time is being wasted on the index scan, but when I didn't use the CASE(just usedArrivalTime`) only 3% were wasted on this index scan. Anyone know the reason for this?

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  • SQL Server store procedure encrypt is safe?

    - by George2
    I am using SQL Server 2008 Enterprise on Windows Server 2003 Enterprise. I developed some store procedure for SQL Server and the machine installed with SQL Server may not be fully under my control (may be used by un-trusted 3rd party). I want to protect my store procedure T-SQL source code (i.e. not viewable by some other party) by using encrypt store procedure function provided by SQL Server. I am not sure whether encrypt store procedure is 100% safe and whether the administrator of the machine (installed with SQL Server) still have ways to view store procedure's source codes? thanks in advance, George

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  • sql - get the latest date of two columns

    - by stacker
    table1 - date1 datetime not null - date2 nvarchar null I want to get the latest date of this two. select date1, date2, (CASE WHEN date1 > CAST(date2 as DateTime) THEN date1 ELSE date2 END) as DateTime) as LatestDate from table1 please note that date2 can be null. in this case, date1 win.

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  • Sql Server Where Case Then Is Null Else Is Not Null

    - by Fabio Montezuma
    I have a procedure which receive a bit variable called @FL_FINALIZADA. If it is null or false I want to restrict my select to show only the rows that contain null DT_FINALIZACAO values. Otherwise I want to show the rows containing not null DT_FINALIZACAO values. Something like this: SELECT * FROM ... WHERE ... AND (OPE.DT_FINALIZACAO = CASE WHEN (@FL_FINALIZADA <> 1) THEN NULL END OR OPE.DT_FINALIZACAO IS NOT NULL) In this case I receive the message: None of the result expressions in a CASE specification can be NULL. How can I achieve this? Thanks in advance.

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  • Help understand difference in sql query

    - by Anil Namde
    Select user_name [User Name], first_name [First Name], last_name [Last Name] Form tab_user ORDER BY user_name Select user_name [User Name], first_name [First Name], last_name [Last Name] Form tab_user ORDER BY User Name Above are the two queries, Is there any difference because of the user_name used instead of User Name Is there something that should be taken care/worried when using something like this.

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  • "lock request time out period exceeded" Error When Trying to See DB Hierarchies

    - by Lloyd Banks
    I have a DB that I can run basic queries (albeit much slower than normal) off of. When I try to see the hierarchy trees for tables, views, or procedures in SSMS Object Explorer, I get the "lock request time out period exceeded". My Report Server reports that run off of objects in this DB are no longer completing. Jobs associated with procedures stored on this DB also do not run. I tried using sp_who2 to find and kill all connections on the DB. This has not solved the problem. What is going on here? How can I resolve this?

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  • SQL Server Performance

    - by khan24
    I have tables in which 35000 to 40000 records are available. Inspite using ajax the performance of the website is very low. Can any body please suggest some ideas or tips for the problem. Thanks in advance.

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  • Pivot Table from data with merged cells

    - by Graeme
    I have a energy spreadsheet for multiple sites. the first row has month and year. the next row has columns for date invoice received, KW hours and cost. So there are three columns for each month. I have merged the month cell across the three columns. When i create a pivot table the date kw/h and costs are labled date1, date2, etc. Can I link the months headings to the subheadings to get meaningful headings in the pivot table????

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  • Big table or multiple separate tables? (database design question)

    - by Khou
    This is a database design question. I want to build an invoice web application, an invoice can have many items, and each user can have an inventory list of product items that they can store and choose to add to an invoice item. My questions are: 1. Should I store all product inventory for all users using my application under one single table? Or have a separate product inventory table created for each user? 2. Is this even possible? 1 table is easier, but what if this single table grows too big, will I have a problem? (primary key INT).

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  • Selecting random top 3 listings per shop for a range of active advertising shops

    - by GraGra33
    I’m trying to display a list of shops each with 3 random items from their shop, if they have 3 or more listings, that are actively advertising. I have 3 tables: one for the shops – “Shops”, one for the listings – “Listings” and one that tracks active advertisers – “AdShops”. Using the below statement, the listings returned are random however I’m not getting exactly 3 listings (rows) returned per shop. SELECT AdShops.ID, Shops.url, Shops.image_url, Shops.user_name AS shop_name, Shops.title, L.listing_id AS listing_id, L.title AS listing_title, L.price as price, L.image_url AS listing_image_url, L.url AS listing_url FROM AdShops INNER JOIN Shops ON AdShops.user_id = Shops.user_id INNER JOIN Listings AS L ON Shops.user_id = L.user_id WHERE (Shops.is_vacation = 0 AND Shops.listing_count > 2 AND L.listing_id IN (SELECT TOP 3 L2.listing_id FROM Listings AS L2 WHERE L2.listing_id IN (SELECT TOP 100 PERCENT L3.listing_id FROM Listings AS L3 WHERE (L3.user_id = L.user_id) ) ORDER BY NEWID() ) ) ORDER BY Shops.shop_name I’m stumped. Anyone have any ideas on how to fix it? The ideal solution would be one record per store with the 3 listings (and associated data) were in columns and not rows – is this possible?

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