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• When/Why to use Cascading in SQL Server?

  - by Joel Coehoorn

  When setting up foreign keys in SQL Server, under what circumstances should you have it cascade on delete or update, and what is the reasoning behind it? This probably applies to other databases as well. I'm looking most of all for concrete examples of each scenario, preferably from someone who has used them successfully.

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• FKs on all tables for status colunm

  - by Jonarch

  I have a colunm "Status" in every table in my DB. The purpose of it is to show if the given row is in use or if it has been deactivated. So values can be (0=deactive and 1= active). Two ways I see this: I can have enums or I am thinking if it is better to keep this colunm as a FK which references the main system data dictionary table which has all the codes used on the system. (website) The benefit is every table, every row can then be centralized through this FK. So if i ever want to check all rows which are deactive on my system i can from this table as all th child tables will have like status = ID 233, where 233 = deactive in the data dictionary table. Any benefit or should i stick with the old way of enums?. Also I am thinking if i need one more status for deleted or is that same as deactivated?

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• MSSQL Server using multiple ID Numbers

  - by vincer

  I have an web application that creates printable forms, these forms have a unique number on them, the problem is I have 2 forms that separate numbers need to be created for them. ie) Form1- Numbered 2000000-2999999 Form2- Numbered 3000000-3999999 dbo.test2 - is my form information table Tsel - is my autoinc table for the 3000000 series numbers Tadv - is my autoinc table for the 2000000 series numbers What I have done is create 2 tables with just autoinc row (one for 2000000 series numbers and one for 3000000 series numbers), I then created a trigger to add a record to the coresponding table, read back the autoinc number and add it to my table that stores the form information including the just created autoinc number for the right series of forms. Although it does work, I'm concerned that the numbers will get messed up under load. I'm not sure the @@IDENTITY will always return the right value when many people are using the system. (I cannot have duplicates and I need to use the numbering form show above. Thanks for any help See code below. ** TRIGGER ** CREATE TRIGGER MAKEANID2 ON dbo.test2 AFTER INSERT AS SET NOCOUNT ON declare @someid int declare @someid2 int declare @startfrom int declare @test1 varchar(10) select @someid=@@IDENTITY select @test1 = (Select name1 from test2 where sysid = @someid ) if @test1 = 'select' begin insert into Tsel Default values select @someid2 = @@IDENTITY end if @test1 = 'adv' begin insert into Tadv Default values select @someid2 = @@IDENTITY end update test2 set name2=(@someid2) where sysid = @someid SET NOCOUNT OFF

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• I built my rails app with sqlite and without specifying any db field sizes, Is my app now foobared for production?

  - by Tim Santeford

  I've been following a lot of good tutorials on building rails apps but I seem to be missing the whole specifying and validating db field sizes part. I love not needing to have to think about it when roughing out an app (I would have never done this with a PHP or ASP.net app). However, now that I'm ready to go to production, I think I might have done myself a disservice by not specifying field sizes as I went. My production db will be MySQL. What is the best practice here? Do I need to go through all of my migration files and specify sizes, update all the models with validation, and update all my form partial views with input max widths? or am I missing a critical step in my development process?

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• Storing user settings in table - how?

  - by Mdillion

  I have settings for the user about 200 settings, these include notice settings and tracing settings from user activities on objects. The problem is how to store it in the DB? Should each setting be a row or a column? If colunm then table will have 200 colunms. If row then about 3 colunms but 200 rows per user x even 10 million users = not good. So how else can i store all these settings? NOTE: these settings are a mix of text entry and FK lookups to other tables. Thanks.

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• what does "out of range" mean?

  - by user329820

  Hi I have checked these statements with mysql and no error will happen and also the out put will be 0 rows BUT my friend checked it and he found an error for SELECT becaouse it is out of range !! IS he correct? thanks CREATE TABLE T1(A INTEGER NULL); SELECT * FROM T1;

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• How to structure a table for additional data if a particular value of an enum/lookup table is chosen

  - by Soliah

  I'd like to store additional data if a particular value is chosen in the enumerated or looked-up column in a table. The obvious option is to have an extra column in the table, but this will lead to a mostly empty column and seems to be like bad approach. Is there another option/method of doing this?

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• Many tables for many users?

  - by Seagull

  I am new to web programming, so excuse the ignorance... ;-) I have a web application that in many ways can be considered to be a multi-tenant environment. By this I mean that each user of the application gets their own 'custom' environment, with absolutely no interaction between those users. So far I have built the web application as a 'single user' environment. In other words, I haven't actually done anything to support multi-users, but only worked on the functionality I want from the app. Here is my problem... What's the best way to build a multi-user environment: All users point to the same 'core' backend. In other words, I build the logic to separate users via appropriate SQL queries (eg. select * from table where user='123' and attribute='456'). Each user points to a unique tablespace, which is built separately as they join the system. In this case I would simply generate ALL the relevant SQL tables per user, with some sort of suffix for the user. (eg. now a query would look like 'select * from table_ where attribute ='456'). In short, it's a difference between "select * from table where USER=" and "select * from table_USER".

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• What is the differnce between an Oracle and Microsoft schema?

  - by Tarzan

  I am working on an enterprise project. Some of the team has an Oracle background and some has a Microsoft SQL Server background. There is much confusion when we talk about schemas. I am trying to provide some clarity. Is this an accurate way to describe the difference in the meaning of schemas between the two technologies? An Oracle schema is associated with a single user and consists of the objects owned by the user. A MS SQL Server schema schema is a namespace.

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• How to represent a 3-way relation with JPA?

  - by simpatico

  A user may have several labels, and links. Then, a user associates a label (or more) to a link. How does one represent the later relationship? A solution could be a many-to-many relationship btw user and link with the optional attribute label. http://en.wikibooks.org/wiki/Java_Persistence/ManyToMany#Mapping_a_Join_Table_with_Additional_Columns In this case the relationship btw user and label may better be 'virtual'. Any alternative I'm not seeing? PS: I've used google bookmarks terminology, as it matches my case quite well.

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• Good basic tutorial for installing and using SqlServer

  - by ripper234

  I know mysql, and I'd like to learn sqlserver. I'm currently stuck on the basics of basics: How to install and configure sql server How to connect to it I installed Sql Server through Web Platform Installer, and have Visual Studio 2008 installed. Still, I can't understand how to connect to my server: I see that the SQL service itself (SQLEXPRESS) is running in both in services.msc and Sql Server Configuration Manager I try to connect to it via the Management Studio, but I don't understand what to do. Where do I begin?

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• Multiple table_prefixes in rails

  - by stevenheidel

  I'm basically looking for a solution to exactly the same problem as described in this dead post: http://railsforum.com/viewtopic.php?pid=88192#p88192 Could someone please advise? Thanks.

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• Will extending the size of a varchar field in MySQL affect the data thats inside it?

  - by barfoon

  I am going to be extending the column from VARCHAR(350) to VARCHAR(800) - will affect any of the strings that are inside the column already?

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• Solr autocommit and autooptimize?

  - by Camran

  I will be uploading my website to a VPS soon. It is a classifieds website which uses Solr integrated with MySql. Solr is updated whenever a new classified is put or deleted. I need a way to make the commit() and optimize() be automated, for example once every 3 hours or so. How can I do this? (Details Please) When is it ideal to optimize? Thanks

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• SQL Server 2005: Rename DB Server Instance Name?

  - by Code Sherpa

  Hi, Can somebody tell me how to rename the DB server instance name and a DB name in SQL Server 2005? Right Now I Have SERVER/OLDNAME -- oldnameDB I want to change the server instance and also change the db name. I have tried: EXEC sp_renamedb 'oldName', 'newName' and that has changed the dbname as it appers in the tree directory. But, when I do "select @@servername" it is the old name. Also, the MDF and LDF files are still the old name. How do change instance and db names as a clean sweep across the server? Thanks.

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• Data Mining In vb.net

  - by user369161

  Hi please give me a simple sample for data mining in vb.net thanks everyone.

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• How to design model for multi-tiered data?

  - by Chris

  Say I have three types of object: Area, Subarea and Topic. I want to be able to display an Area, which is just a list of Subareas and the Topics contained in those Subareas. I never want to be able to display Subareas separately - they're just for breaking up the Topics. Topics can, however, appear in multiple Areas (but probably under the same Subarea). How would I design a model for this? I could use ForeignKey from Topic to Subarea and from Subarea to Area, but it seems unnecessarily complex given that I never want to interact with subareas themselves. Also, none of these objects are ever altered or added to by the user. They're just for me to represent information. Maybe there is a better way to represent it all?

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• using dummy row with NOT NULL to solve DEFAUT NULL

  - by Tony38

  I know having DEFAULT NULLS is not a good practice but I have many optional lookup values which are FK in the system so to solve this issue here is what i am doing: I use NOT NULL for every FK / lookup valve field. I have the first row in every table which is PK id = 1 as a dummy row with just "none" in all the columns. this way I can use NOT NULL in my schema and if needed reference to the none row values which should be null. Is this a good design or any other work arounds?

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• Are zip code and postal code violation of 3rd normal form?

  - by ojblass

  Given that state information is implicit in the zip code aren't storing both of them some violaiton of third normal form? Can or should you simply combine them into one field?

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• Aggregation over a few models - Django

  - by RadiantHex

  Hi folks, I'm trying to compute the average of a field over various subsets of a queryset. Player.objects.order_by('-score').filter(sex='male').aggregate(Avg('level')) This works perfectly! But... if I try to compute it for the top 50 players it does not work. Player.objects.order_by('-score').filter(sex='male')[:50].aggregate(Avg('level')) This last one returns the exact same result as the query above it, which is wrong. What am I doing wrong? Help would be very much appreciated!

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• Static selection and Ruby on Rails objects

  - by Dave

  Hi all- I have a simple problem, but am having trouble wrapping my head around it. I have an video object that should have one or more "genres". This list of genres should be prepopulated and then the user should just select one or more using autocomplete or some such. Here is the question: Is it worth creating a table with genres for the static selection? Or should it just be included in the presentation layer? If there is a static table, how do we name it correctly. I envision something like this class Video < ActiveRecord::Base has_many :genres ... end class Genre < ... belongs_to :video ... end But then we get a table called genre, that basically maps all the selected genres to their parent videos. There would need to be some static table to reference the static genres. Is this the best way to do it? Sorry if this was rambl-y a little stream of conciousness. Thanks!

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• get n records at a time from a temporary table

  - by Claudiu

  I have a temporary table with about 1 million entries. The temporary table stores the result of a larger query. I want to process these records 1000 at a time, for example. What's the best way to set up queries such that I get the first 1000 rows, then the next 1000, etc.? They are not inherently ordered, but the temporary table just has one column with an ID, so I can order it if necessary. I was thinking of creating an extra column with the temporary table to number all the rows, something like: CREATE TEMP TABLE tmptmp AS SELECT ##autonumber somehow##, id FROM .... --complicated query then I can do: SELECT * FROM tmptmp WHERE autonumber>=0 AND autonumber < 1000 etc... how would I actually accomplish this? Or is there a better way? I'm using Python and PostgreSQL.

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• help with delete where not in query

  - by kralco626

  I have a lookup table (##lookup). I know it's bad design because I'm duplicating data, but it speeds up my queries tremendously. I have a query that populates this table insert into ##lookup select distinct col1,col2,... from table1...join...etc... I would like to simulate this behavior: delete from ##lookup insert into ##lookup select distinct col1,col2,... from table1...join...etc... This would clearly update the table correctly. But this is a lot of inserting and deleting. It messes with my indexes and locks up the table for selecting from. This table could also be updated by something like: delete from ##lookup where not in (select distinct col1,col2,... from table1...join...etc...) insert into ##lookup (select distinct col1,col2,... from table1...join...etc...) except if it is already in the table The second way may take longer, but I can say "with no lock" and I will be able to select from the table. Any ideas on how to write the query the second way?

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• What is better sql string or stored procedures?

  - by Sem Dendoncker

  Hello, I have a dataaccesslayer which uses Enterprice libraries. Now I was wondering what is better? Using stored procedures to create my sql or writing sql strings within the dataaccess classes? Cheers, M

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• MySQL Limiting a query to one consistent value

  - by Lucas Matos

  My current query returns a table like: +------------+ value1 | .... value1 | .... value2 | .... value3 | .... +------------+ I want: +------------+ value1 | .... value1 | .... +------------+ I want to only receive all rows with the first value. Normally I would do a WHERE clause if I knew that value, and I cannot use a LIMIT because each value has a different number of rows. Right now My query looks like "SELECT u.*, n.something, w.* FROM ... AS u, ... AS n, ... AS w WHERE u.id = n.id AND w.val = n.val AND u.desc LIKE '%GET REQUEST VARIABLE%';" This works great, except I get way too many rows and using PHP to do this ruins code portability and is superfluous. Thanks for reading

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