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  • Query to return substring from string in SQL Server

    - by Jowie
    I have a user defined function called Sync_CheckData under Scalar-valued functions in Microsoft SQL Server. What it actually does is to check the quantity of issued product and balance quantity are the same. If something is wrong, returns an ErrorStr nvarchar(255). Output Example: Balance Stock Error for Product ID : 4 From the above string, I want to get 4 so that later on I can SELECT the rows which is giving errors by using WHERE clause (WHERE Product_ID = 4). Which SQL function can I use to get the substring?

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  • Loop through non-integer rows using SQL

    - by Jesse
    I know how to accomplish my task with .NET, but I wanted to do this just in SQL. I need to loop through all of the rows where the primary key is somewhat arbitrary. It can be a number or a series of letters, and probably any number of unusual things. I know I could do something like this... DECLARE @numRows INT SET @numRows = (SELECT COUNT(pkField) FROM myTable) DECLARE @I INT SET @I = 1 WHILE (@I <= @numRows) BEGIN --Do what I need to here SET @I = @I + 1 END ...if my rows were indexed in a contiguous fashion, but I don't know enough about SQL to do that if they're not. I keep coming across the use of "cursors," but I come across just as much reading about avoiding cursors. I found this SO solution but I'm not sure if that's what I'm needing? I appreciate any ideas.

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  • See queries that hit SQL

    - by Shaded
    I have a really basic stupid easy question about sql... and I'll probably get -100 points... but here it goes anyway... Is there a way using sql 2008 Management Studio to look at the queries that hit the server? I'm trying to debug a program and I get messages like "Incorrect syntax near the keyword 'AND'". Since the queries are being dynamically generated it's a hassle to figure out what is going to the server. Any help is appreciated!

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  • Cannot find the certificate

    - by user409756
    We get a T-SQL (SQL Server 2008 R2) error on BACKUP CERTIFICATE: ERROR_NUMBER 15151, SEVERITY 16, STATE 1, PROCEDURE -, LINE 8, MESSAGE: Cannot find the certificate 'certificate1', because it does not exist or you do not have permission. We can see the certificate in master.sys.certificates. Our pseudo-code: copy an unattached template_db to db1 attach db1 create certificate1 (in stored procedure in master db) generate @password CREATE DATABASE ENCRYPTION KEY … ENCRYPTION BY SERVER CERTIFICATE '+@certificate_name +… (in stored procedure in db1) turn on Transparent Database Encryption for db1 using certificate1. (N'ALTER DATABASE '+@db_name+N' SET ENCRYPTION ON') N’BACKUP CERTIFICATE '+@certificate_name+N' TO FILE = '''+@certificate_file_path+N''' WITH PRIVATE KEY ( FILE = '''+@private_key_file_path+N''', ENCRYPTION BY PASSWORD = '''+@password+N'''' To try to work-around the error, we tested three ways with the BACKUP CERTIFICATE code in a different databases each time, including db1 and master. All get the same error. Any ideas? Thanks.

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  • How would I duplicate the Rank function in a Sql Server Compact Edition SELECT statement?

    - by AMissico
    It doesn't look like SQL Server Compact Edition supports the RANK() function. (See Functions (SQL Server Compact Edition) at http://msdn.microsoft.com/en-us/library/ms174077(SQL.90).aspx). How would I duplicate the RANK() function in a SQL Server Compact Edition SELECT statement. (Please use Northwind.sdf for any sample select statements, as it is the only one I can open with SQL Server 2005 Management Studio.)

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  • How to Create Views for All Tables with Oracle SQL Developer

    - by thatjeffsmith
    Got this question over the weekend via a friend and Oracle ACE Director, so I thought I would share the answer here. If you want to quickly generate DDL to create VIEWs for all the tables in your system, the easiest way to do that with SQL Developer is to create a data model. Wait, why would I want to do this? StackOverflow has a few things to say on this subject… So, start with importing a data dictionary. Step One: Open of Create a Model In SQL Developer, go to View – Data Modeler – Browser. Then in the browser panel, expand your design and create a new Relational Model. Step Two: Import your Data Dictionary This is a fancy way of saying, ‘suck objects out of the database into my model’ This will open a wizard to connect, select your schema(s), objects, etc. Once they’re in your model, you’re ready to cook with gas I’m using HR (Human Resources) for this example. You should end up with something that looks like this. Our favorite HR model Now we’re ready to generate the views! Step Three: Auto-generate the Views Go to Tools – Data Modeler – Table to View Wizard. I don’t want all my tables included, and I want to change the naming standard Decide if you want to change the default generated view names By default the views will be created as ‘V_TABLE_NAME.’ If you don’t like the ‘V_’ you can enter your own. You also can reference the object and model name with variables as shown in the screenshot above. I’m going to go with something a little more personal. The views are the little green boxes in the diagram Can’t find your views? They should be grouped together in your diagram. Don’t forget to use the Navigator to easily find and navigate to those model diagram objects! Step Four: Generate the DDL Ok, let’s use the Generate DDL button on the toolbar. Un-check everything but your views If you used a prefix, take advantage of that to create a filter. You might have existing views in your model that you don’t want to include, right? Once you click ‘OK’ the DDL will be generated. -- Generated by Oracle SQL Developer Data Modeler 4.0.0.825 -- at: 2013-11-04 10:26:39 EST -- site: Oracle Database 11g -- type: Oracle Database 11g CREATE OR REPLACE VIEW HR.TJS_BLOG_COUNTRIES ( COUNTRY_ID , COUNTRY_NAME , REGION_ID ) AS SELECT COUNTRY_ID , COUNTRY_NAME , REGION_ID FROM HR.COUNTRIES ; CREATE OR REPLACE VIEW HR.TJS_BLOG_EMPLOYEES ( EMPLOYEE_ID , FIRST_NAME , LAST_NAME , EMAIL , PHONE_NUMBER , HIRE_DATE , JOB_ID , SALARY , COMMISSION_PCT , MANAGER_ID , DEPARTMENT_ID ) AS SELECT EMPLOYEE_ID , FIRST_NAME , LAST_NAME , EMAIL , PHONE_NUMBER , HIRE_DATE , JOB_ID , SALARY , COMMISSION_PCT , MANAGER_ID , DEPARTMENT_ID FROM HR.EMPLOYEES ; CREATE OR REPLACE VIEW HR.TJS_BLOG_JOBS ( JOB_ID , JOB_TITLE , MIN_SALARY , MAX_SALARY ) AS SELECT JOB_ID , JOB_TITLE , MIN_SALARY , MAX_SALARY FROM HR.JOBS ; CREATE OR REPLACE VIEW HR.TJS_BLOG_JOB_HISTORY ( EMPLOYEE_ID , START_DATE , END_DATE , JOB_ID , DEPARTMENT_ID ) AS SELECT EMPLOYEE_ID , START_DATE , END_DATE , JOB_ID , DEPARTMENT_ID FROM HR.JOB_HISTORY ; CREATE OR REPLACE VIEW HR.TJS_BLOG_LOCATIONS ( LOCATION_ID , STREET_ADDRESS , POSTAL_CODE , CITY , STATE_PROVINCE , COUNTRY_ID ) AS SELECT LOCATION_ID , STREET_ADDRESS , POSTAL_CODE , CITY , STATE_PROVINCE , COUNTRY_ID FROM HR.LOCATIONS ; CREATE OR REPLACE VIEW HR.TJS_BLOG_REGIONS ( REGION_ID , REGION_NAME ) AS SELECT REGION_ID , REGION_NAME FROM HR.REGIONS ; -- Oracle SQL Developer Data Modeler Summary Report: -- -- CREATE TABLE 0 -- CREATE INDEX 0 -- ALTER TABLE 0 -- CREATE VIEW 6 -- CREATE PACKAGE 0 -- CREATE PACKAGE BODY 0 -- CREATE PROCEDURE 0 -- CREATE FUNCTION 0 -- CREATE TRIGGER 0 -- ALTER TRIGGER 0 -- CREATE COLLECTION TYPE 0 -- CREATE STRUCTURED TYPE 0 -- CREATE STRUCTURED TYPE BODY 0 -- CREATE CLUSTER 0 -- CREATE CONTEXT 0 -- CREATE DATABASE 0 -- CREATE DIMENSION 0 -- CREATE DIRECTORY 0 -- CREATE DISK GROUP 0 -- CREATE ROLE 0 -- CREATE ROLLBACK SEGMENT 0 -- CREATE SEQUENCE 0 -- CREATE MATERIALIZED VIEW 0 -- CREATE SYNONYM 0 -- CREATE TABLESPACE 0 -- CREATE USER 0 -- -- DROP TABLESPACE 0 -- DROP DATABASE 0 -- -- REDACTION POLICY 0 -- -- ERRORS 0 -- WARNINGS 0 You can then choose to save this to a file or not. This has a few steps, but as the number of tables in your system increases, so does the amount of time this feature can save you!

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  • System Variables, Stored Procedures or Functions for Meta Data

    - by BuckWoody
    Whenever you want to know something about SQL Server’s configuration, whether that’s the Instance itself or a database, you have a few options. If you want to know “dynamic” data, such as how much memory or CPU is consumed or what a particular query is doing, you should be using the Dynamic Management Views (DMVs) that you can read about here: http://msdn.microsoft.com/en-us/library/ms188754.aspx  But if you’re looking for how much memory is installed on the server, the version of the Instance, the drive letters of the backups and so on, you have other choices. The first of these are system variables. You access these with a SELECT statement, and they are useful when you need a discrete value for use, say in another query or to put into a table. You can read more about those here: http://msdn.microsoft.com/en-us/library/ms173823.aspx You also have a few stored procedures you can use. These often bring back a lot more data, pre-formatted for the screen. You access these with the EXECUTE syntax. It is a bit more difficult to take the data they return and get a single value or place the results in another table, but it is possible. You can read more about those here: http://msdn.microsoft.com/en-us/library/ms187961.aspx Yet another option is to use a system function, which you access with a SELECT statement, which also brings back a discrete value that you can use in a test or to place in another table. You can read about those here: http://msdn.microsoft.com/en-us/library/ms187812.aspx  By the way, many of these constructs simply query from tables in the master or msdb databases for the Instance or the system tables in a user database. You can get much of the information there as well, and there are even system views in each database to show you the meta-data dealing with structure – more on that here: http://msdn.microsoft.com/en-us/library/ms186778.aspx  Some of these choices are the only way to get at a certain piece of data. But others overlap – you can use one or the other, they both come back with the same data. So, like many Microsoft products, you have multiple ways to do the same thing. And that’s OK – just research what each is used for and how it’s intended to be used, and you’ll be able to select (pun intended) the right choice. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Export all SSIS packages from msdb using Powershell

    - by jamiet
    Have you ever wanted to dump all the SSIS packages stored in msdb out to files? Of course you have, who wouldn’t? Right? Well, at least one person does because this was the subject of a thread (save all ssis packages to file) on the SSIS forum earlier today. Some of you may have already figured out a way of doing this but for those that haven’t here is a nifty little script that will do it for you and it uses our favourite jack-of-all tools … Powershell!! Imagine I have the following package folder structure on my Integration Services server (i.e. in [msdb]): There are two packages in there called “20110111 Chaining Expression components” & “Package”, I want to export those two packages into a folder structure that mirrors that in [msdb]. Here is the Powershell script that will do that:Param($SQLInstance = "localhost") #####Add all the SQL goodies (including Invoke-Sqlcmd)##### add-pssnapin sqlserverprovidersnapin100 -ErrorAction SilentlyContinue add-pssnapin sqlservercmdletsnapin100 -ErrorAction SilentlyContinue cls $Packages = Invoke-Sqlcmd -MaxCharLength 10000000 -ServerInstance $SQLInstance -Query "WITH cte AS ( SELECT cast(foldername as varchar(max)) as folderpath, folderid FROM msdb..sysssispackagefolders WHERE parentfolderid = '00000000-0000-0000-0000-000000000000' UNION ALL SELECT cast(c.folderpath + '\' + f.foldername as varchar(max)), f.folderid FROM msdb..sysssispackagefolders f INNER JOIN cte c ON c.folderid = f.parentfolderid ) SELECT c.folderpath,p.name,CAST(CAST(packagedata AS VARBINARY(MAX)) AS VARCHAR(MAX)) as pkg FROM cte c INNER JOIN msdb..sysssispackages p ON c.folderid = p.folderid WHERE c.folderpath NOT LIKE 'Data Collector%'" Foreach ($pkg in $Packages) { $pkgName = $Pkg.name $folderPath = $Pkg.folderpath $fullfolderPath = "c:\temp\$folderPath\" if(!(test-path -path $fullfolderPath)) { mkdir $fullfolderPath | Out-Null } $pkg.pkg | Out-File -Force -encoding ascii -FilePath "$fullfolderPath\$pkgName.dtsx" } To run it simply change the “localhost” parameter of the server you want to connect to either by editing the script or passing it in when the script is executed. It will create the folder structure in C:\Temp (which you can also easily change if you so wish – just edit the script accordingly). Here’s the folder structure that it created for me: Notice how it is a mirror of the folder structure in [msdb]. Hope this is useful! @Jamiet UPDATE: THis post prompted Chad Miller to write a post describing his Powershell add-in that utilises a SSIS API to do exporting of packages. Go take a read here: http://sev17.com/2011/02/importing-and-exporting-ssis-packages-using-powershell/

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  • Export all SSIS packages from msdb using Powershell

    - by jamiet
    Have you ever wanted to dump all the SSIS packages stored in msdb out to files? Of course you have, who wouldn’t? Right? Well, at least one person does because this was the subject of a thread (save all ssis packages to file) on the SSIS forum earlier today. Some of you may have already figured out a way of doing this but for those that haven’t here is a nifty little script that will do it for you and it uses our favourite jack-of-all tools … Powershell!!   Imagine I have the following package folder structure on my Integration Services server (i.e. in [msdb]): There are two packages in there called “20110111 Chaining Expression components” & “Package”, I want to export those two packages into a folder structure that mirrors that in [msdb]. Here is the Powershell script that will do that:   Param($SQLInstance = "localhost") #####Add all the SQL goodies (including Invoke-Sqlcmd)##### add-pssnapin sqlserverprovidersnapin100 -ErrorAction SilentlyContinue add-pssnapin sqlservercmdletsnapin100 -ErrorAction SilentlyContinue cls $Packages = Invoke-Sqlcmd -MaxCharLength 10000000 -ServerInstance $SQLInstance -Query "WITH cte AS ( SELECT cast(foldername as varchar(max)) as folderpath, folderid FROM msdb..sysssispackagefolders WHERE parentfolderid = '00000000-0000-0000-0000-000000000000' UNION ALL SELECT cast(c.folderpath + '\' + f.foldername as varchar(max)), f.folderid FROM msdb..sysssispackagefolders f INNER JOIN cte c ON c.folderid = f.parentfolderid ) SELECT c.folderpath,p.name,CAST(CAST(packagedata AS VARBINARY(MAX)) AS VARCHAR(MAX)) as pkg FROM cte c INNER JOIN msdb..sysssispackages p ON c.folderid = p.folderid WHERE c.folderpath NOT LIKE 'Data Collector%'" Foreach ($pkg in $Packages) { $pkgName = $Pkg.name $folderPath = $Pkg.folderpath $fullfolderPath = "c:\temp\$folderPath\" if(!(test-path -path $fullfolderPath)) { mkdir $fullfolderPath | Out-Null } $pkg.pkg | Out-File -Force -encoding ascii -FilePath "$fullfolderPath\$pkgName.dtsx" }   To run it simply change the “localhost” parameter of the server you want to connect to either by editing the script or passing it in when the script is executed. It will create the folder structure in C:\Temp (which you can also easily change if you so wish – just edit the script accordingly). Here’s the folder structure that it created for me: Notice how it is a mirror of the folder structure in [msdb]. Hope this is useful! @Jamiet

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  • Collation errors in business

    - by Rob Farley
    At the PASS Summit last month, I did a set (Lightning Talk) about collation, and in particular, the difference between the “English” spoken by people from the US, Australia and the UK. One of the examples I gave was that in the US drivers might stop for gas, whereas in Australia, they just open the window a little. This is what’s known as a paraprosdokian, where you suddenly realise you misunderstood the first part of the sentence, based on what was said in the second. My current favourite is Emo Phillip’s line “I like to play chess with old men in the park, but it can be hard to find thirty-two of them.” Essentially, this a collation error, one that good comedians can get mileage from. Unfortunately, collation is at its worst when we have a computer comparing two things in different collations. They might look the same, and sound the same, but if one of the things is in SQL English, and the other one is in Windows English, the poor database server (with no sense of humour) will get suspicious of developers (who all have senses of humour, obviously), and declare a collation error, worried that it might not realise some nuance of the language. One example is the common scenario of a case-sensitive collation and a case-insensitive one. One may think that “Rob” and “rob” are the same, but the other might not. Clearly one of them is my name, and the other is a verb which means to steal (people called “Nick” have the same problem, of course), but I have no idea whether “Rob” and “rob” should be considered the same or not – it depends on the collation. I told a lie before – collation isn’t at its worst in the computer world, because the computer has the sense to complain about the collation issue. People don’t. People will say something, with their own understanding of what they mean. Other people will listen, and apply their own collation to it. I remember when someone was asking me about a situation which had annoyed me. They asked if I was ‘pissed’, and I said yes. I meant that I was annoyed, but they were asking if I’d been drinking. It took a moment for us to realise the misunderstanding. In business, the problem is escalated. A business user may explain something in a particular way, using terminology that they understand, but using words that mean something else to a technical person. I remember a situation with a checkbox on a form (back in VB6 days from memory). It was used to indicate that something was approved, and indicated whether a particular database field should store True or False – nothing more. However, the client understood it to mean that an entire workflow system would be implemented, with different users have permission to approve items and more. The project manager I’d just taken over from clearly hadn’t appreciated that, and I faced a situation of explaining the misunderstanding to the client. Lots of fun... Collation errors aren’t just a database setting that you can ignore. You need to remember that Americans speak a different type of English to Aussies and Poms, and techies speak a different language to their clients.

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  • Cloud – the forecast is improving

    - by Rob Farley
    There is a lot of discussion about “the cloud”, and how that affects people’s data stories. Today the discussion enters the realm of T-SQL Tuesday, hosted this month by Jorge Segarra. Over the years, companies have invested a lot in making sure that their data is good, and I mean every aspect of it – the quality of it, the security of it, the performance of it, and more. Experts such as those of us at LobsterPot Solutions have helped these companies with this, and continue to work with clients to make sure that data is a strong part of their business, not an oversight. Whether business intelligence systems are being utilised or not, every business needs to be able to rely on its data, and have the confidence in it. Data should be a foundation upon which a business is built. In the past, data had been stored in paper-based systems. Filing cabinets stored vital information. Today, people have server rooms with storage of various kinds, recognising that filing cabinets don’t necessarily scale particularly well. It’s easy to ‘lose’ data in a filing cabinet, when you have people who need to make sure that the sheets of paper are in the right spot, and that you know how things are stored. Databases help solve that problem, but still the idea of a large filing cabinet continues, it just doesn’t involve paper. If something happens to the physical ‘filing cabinet’, then the problems are larger still. Then the data itself is under threat. Many clients have generators in case the power goes out, redundant cables in case the connectivity dies, and spare servers in other buildings just in case they’re required. But still they’re maintaining filing cabinets. You see, people like filing cabinets. There’s something to be said for having your data ‘close’. Even if the data is not in readable form, living as bits on a disk somewhere, the idea that its home is ‘in the building’ is comforting to many people. They simply don’t want to move their data anywhere else. The cloud offers an alternative to this, and the human element is an obstacle. By leveraging the cloud, companies can have someone else look after their filing cabinet. A lot of people really don’t like the idea of this, partly because the administrators of the data, those people who could potentially log in with escalated rights and see more than they should be allowed to, who need to be trusted to respond if there’s a problem, are now a faceless entity in the cloud. But this doesn’t mean that the cloud is bad – this is simply a concern that some people may have. In new functionality that’s on its way, we see other hybrid mechanisms that mean that people can leverage parts of the cloud with less fear. Companies can use cloud storage to hold their backup data, for example, backups that have been encrypted and are therefore not able to be read by anyone (including administrators) who don’t have the right password. Companies can have a database instance that runs locally, but which has its data files in the cloud, complete with Transparent Data Encryption if needed. There can be a higher level of control, making the change easier to accept. Hybrid options allow people who have had fears (potentially very justifiable) to take a new look at the cloud, and to start embracing some of the benefits of the cloud (such as letting someone else take care of storage, high availability, and more) without losing the feeling of the data being close. @rob_farley

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  • My server is slower than the average user's computer, should I still offload Access queries to SQL Server? [closed]

    - by andrewb
    Possible Duplicate: How do you do Load Testing and Capacity Planning for Databases I have a database set up with MS Access 2007 front ends and an SQL Server 2005 back end. At the moment, all the queries are saved in the front end as I've only recently moved to an SQL Server backend. I'm wondering how much of those queries I should save as stored procedures/views on SQL Server. About the system The number of concurrent users is only a handful, though it could be as high as 25 at one time (very unlikely). The average computer has an Intel i3-2120 CPU running at 3.3 GHz, which gets a PassMark score of 3,987, whilst the server has an Intel Xeon E5335 running at 2.0 GHz, which gets a PassMark score of 2,637. Always an awkward situation when an i3 outperforms a Xeon... though the i3 is from Q1 2011 and the Xeon is Q2 2009. There is potential for a server upgrade in the future, though it wouldn't come easy. I'm inclined to move the queries to the back end, as they are beginning to take noticeable time and I figure that is a better way of doing things. I like the idea of throwing everything at the server, then pushing for a server upgrade. It makes more sense in my mind to be upgrading one server rather than 30 PCs. Or am I being overzealous? Why my question isn't a duplicate It seems that my question has been misinterpreted and labelled a duplicate of quite a different question, one about testing and capacity planning. I'll try explain how my question is very different from the linked question. The crux of my question is something like "Even though my server is technically slower, is it better to have it doing more of the queries?" There's two ways that people could have answered this: I agree the server is going to be slower, but the extra benefits of such and such (like the less Access the better) means you should move most to the server anyway. (OR no it doesn't outweigh the benefit, keep them in Access) Actually the server will be faster because of such and such. I'm hoping that people out there could provide some answers like this, and the question in the dupe link doesn't really provide either of these answers. Ok sure, I suppose I could do extensive performance testing to compare Access queries running on a local machine to SQL Server queries running on the server, but that sounds like a very hard task (particularly performance testing of access) compared to someone giving some quick general guidance, and again, my question is looking for a lot more than immediate performance benefit.

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  • Install Sql Server Developer Edition 32-bit (or Enterprise Edition) on Windows 7 Home Premium 64-bit

    - by ali62b
    Is there any work around to Successfully install SQL server 2008 32-bit on Windows 7 Home premium 64-bit ? If this is the case I first installed VS 2008 SP 1 on my machine and when I click on install.exe file for installing SQL Server 2008 (Developer Edition) I get an error related to .NET Framework version which is installed already on my PC. { I get the same error trying to install Enterprise Edition}

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  • How do I get SQL Profiler to show statements with column names like 'password'?

    - by Kev
    I'm profiling a database just now and need to see the UPDATE and INSERT statements being executed on a particular table. However, because the table has a 'Password' column the SQL Profiler is being understandingly cautious and replacing the TextData column with: -- 'password' was found in the text of this event. -- The text has been replaced with this comment for security reasons. How do I prevent it doing this because I need to see the SQL statement being executed?

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  • SQL Server Express with Advanced Services (with Reporting Services)???

    - by Fretwizard
    I have tried to download SQL Server 2005 Express edition about 4 times trying to find the correct version that has business intelligence studio and reporting services in it? Every time I try to unhide the advanced configuration during install, it's never there... Can anyone point me to the correct download? Looking for 2005 (not 2008) because my work SQL server that I am trying to learn this for is 2005, and the training material I have is for 2005 and VS 2008 does not want to integrate with SQL2008 express.

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  • Alias a linked Server in SQL server management studio?

    - by absentmindeduk
    Hoping someone can help - is there a way in SQL server management studio 2008 R2 that I can alias a linked SQL server? I have a server, added by IP address, to which I do not have the login credentials - however as the connection is already setup I can login ok. Issue is that, this is a dev environment, prior to a live deployment and the IP I have as a linked server needs to be 'accessible' by my stored procs under a different name, eg 'myserver' not 192.168.xxx.xxx... Any help much appreciated.

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  • Joins in single-table queries

    - by Rob Farley
    Tables are only metadata. They don’t store data. I’ve written something about this before, but I want to take a viewpoint of this idea around the topic of joins, especially since it’s the topic for T-SQL Tuesday this month. Hosted this time by Sebastian Meine (@sqlity), who has a whole series on joins this month. Good for him – it’s a great topic. In that last post I discussed the fact that we write queries against tables, but that the engine turns it into a plan against indexes. My point wasn’t simply that a table is actually just a Clustered Index (or heap, which I consider just a special type of index), but that data access always happens against indexes – never tables – and we should be thinking about the indexes (specifically the non-clustered ones) when we write our queries. I described the scenario of looking up phone numbers, and how it never really occurs to us that there is a master list of phone numbers, because we think in terms of the useful non-clustered indexes that the phone companies provide us, but anyway – that’s not the point of this post. So a table is metadata. It stores information about the names of columns and their data types. Nullability, default values, constraints, triggers – these are all things that define the table, but the data isn’t stored in the table. The data that a table describes is stored in a heap or clustered index, but it goes further than this. All the useful data is going to live in non-clustered indexes. Remember this. It’s important. Stop thinking about tables, and start thinking about indexes. So let’s think about tables as indexes. This applies even in a world created by someone else, who doesn’t have the best indexes in mind for you. I’m sure you don’t need me to explain Covering Index bit – the fact that if you don’t have sufficient columns “included” in your index, your query plan will either have to do a Lookup, or else it’ll give up using your index and use one that does have everything it needs (even if that means scanning it). If you haven’t seen that before, drop me a line and I’ll run through it with you. Or go and read a post I did a long while ago about the maths involved in that decision. So – what I’m going to tell you is that a Lookup is a join. When I run SELECT CustomerID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 285; against the AdventureWorks2012 get the following plan: I’m sure you can see the join. Don’t look in the query, it’s not there. But you should be able to see the join in the plan. It’s an Inner Join, implemented by a Nested Loop. It’s pulling data in from the Index Seek, and joining that to the results of a Key Lookup. It clearly is – the QO wouldn’t call it that if it wasn’t really one. It behaves exactly like any other Nested Loop (Inner Join) operator, pulling rows from one side and putting a request in from the other. You wouldn’t have a problem accepting it as a join if the query were slightly different, such as SELECT sod.OrderQty FROM Sales.SalesOrderHeader AS soh JOIN Sales.SalesOrderDetail as sod on sod.SalesOrderID = soh.SalesOrderID WHERE soh.SalesPersonID = 285; Amazingly similar, of course. This one is an explicit join, the first example was just as much a join, even thought you didn’t actually ask for one. You need to consider this when you’re thinking about your queries. But it gets more interesting. Consider this query: SELECT SalesOrderID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 276 AND CustomerID = 29522; It doesn’t look like there’s a join here either, but look at the plan. That’s not some Lookup in action – that’s a proper Merge Join. The Query Optimizer has worked out that it can get the data it needs by looking in two separate indexes and then doing a Merge Join on the data that it gets. Both indexes used are ordered by the column that’s indexed (one on SalesPersonID, one on CustomerID), and then by the CIX key SalesOrderID. Just like when you seek in the phone book to Farley, the Farleys you have are ordered by FirstName, these seek operations return the data ordered by the next field. This order is SalesOrderID, even though you didn’t explicitly put that column in the index definition. The result is two datasets that are ordered by SalesOrderID, making them very mergeable. Another example is the simple query SELECT CustomerID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 276; This one prefers a Hash Match to a standard lookup even! This isn’t just ordinary index intersection, this is something else again! Just like before, we could imagine it better with two whole tables, but we shouldn’t try to distinguish between joining two tables and joining two indexes. The Query Optimizer can see (using basic maths) that it’s worth doing these particular operations using these two less-than-ideal indexes (because of course, the best indexese would be on both columns – a composite such as (SalesPersonID, CustomerID – and it would have the SalesOrderID column as part of it as the CIX key still). You need to think like this too. Not in terms of excusing single-column indexes like the ones in AdventureWorks2012, but in terms of having a picture about how you’d like your queries to run. If you start to think about what data you need, where it’s coming from, and how it’s going to be used, then you will almost certainly write better queries. …and yes, this would include when you’re dealing with regular joins across multiples, not just against joins within single table queries.

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