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  • How would I implement separate databases for reading and writing operations?

    - by Matt
    I am interested in implementing an architecture that has two databases one for read operations and the other for writes. I have never implemented something like this and have always built single database, highly normalised systems so I am not quite sure where to begin. I have a few parts to this question. 1. What would be a good resource to find out more about this achitecture? 2. Is it just a question of replicating between two identical schemas, or would your schemas differ depending on the operations, would normalisation vary too? 3. How do you insure that data written to one database is immediately available for reading from the second? Any further help, tips, resources would be appreciated. Thanks.

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  • Check for active connection in NHibernate

    - by Dofs
    I have a system with a few different databases, and I would like to check if a certain database is down, and if so display a message to the user. Is it possible in NHibernate to check if there is an active connection to the database, without having to request data and then catch the exception?

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  • Filling a LOV in Oracle Apex based on data in another text box

    - by Martin Pugh
    I am fairly new to Oracle Apex, and have a problem. Our application currently has a method of entering data, with several text boxes and Optional List of Values. I would like to have an LOV based on information in another text box like so: select APPOINTMENT_ID PATIENT_ID from APPOINTMENT where PATIENT_ID = :P9_PAT_NUM where P9_PAT_NUM is a patient number in a text box. However, this would apparently only work if the text box has already been submitted, else it assumes the text box is null. Is there any way to get this working with an LOV, or perhaps some other method?

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  • how to combine the related version in group by

    - by randeepsp
    select count(a),b,c from APPLE join MANGO on (APPLE.link=MANGO.link) join ORANGE on (APPLE.link=ORANGE.link) where id='camel' group by b,c; the column b gives values like 1.0 1.0,R 1.0,B 2.0 2.0,B 2.0,R 3.0,C 3.0,R is there a way to modify the above quer so that all 1.0 and 1.0,R and 1.0,B are merged as 1.0 and 2.0,2.0,B are merged as 2.0 and same way for 3.0 and 4.0

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  • FluentNHibernate error -- "Invalid object name"

    - by goober
    I'm attempting to do the most simple of mappings with FluentNHibernate & Sql2005. Basically, I have a database table called "sv_Categories". I'd like to add a category, setting the ID automatically, and adding the userid and title supplied. Database table layout: CategoryID -- int -- not-null, primary key, auto-incrementing UserID -- uniqueidentifier -- not null Title -- varchar(50) -- not null Simple. My SessionFactory code (which works, as far as I can tell): _SessionFactory = Fluently.Configure().Database( MsSqlConfiguration.MsSql2005 .ConnectionString(c => c.FromConnectionStringWithKey("SVTest"))) .Mappings(x => x.FluentMappings.AddFromAssemblyOf<CategoryMap>()) .BuildSessionFactory(); My ClassMap code: public class CategoryMap : ClassMap<Category> { public CategoryMap() { Id(x => x.ID).Column("CategoryID").Unique(); Map(x => x.Title).Column("Title").Not.Nullable(); Map(x => x.UserID).Column("UserID").Not.Nullable(); } } My Class code: public class Category { public virtual int ID { get; private set; } public virtual string Title { get; set; } public virtual Guid UserID { get; set; } public Category() { // do nothing } } And the page where I save the object: public void Add(Category catToAdd) { using (ISession session = SessionProvider.GetSession()) { using (ITransaction Transaction = session.BeginTransaction()) { session.Save(catToAdd); Transaction.Commit(); } } } I receive the error Invalid object name 'Category'. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.SqlClient.SqlException: Invalid object name 'Category'. I think it might be that I haven't told the CategoryMap class to use the "sv_Categories" table, but I'm not sure how to do that. Any help would be appreciated. Thanks!

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  • Union Distinct rows but order them by number of occurrences in mysql

    - by Baversjo
    Hi I have the following query: SELECT o.id,o.name FROM object o WHERE ( o.description LIKE '%Black%' OR o.name LIKE '%Black%' ) UNION ALL SELECT o2.id,o2.name FROM object o2 WHERE ( o2.description LIKE '%iPhone%' OR o2.name LIKE '%iPhone%' ) Which procude the following: id name 2 New Black iPhone 1 New White iPhone 2 New Black iPhone I would like to UNION DISTINCT, but I would also like the result ordered by the number of occurrences of each identical row (primary: id).

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  • Exporting many tables on Oracle

    - by Adomas
    Hi, I would like to know, how to export many tables from oracle DB. I use exp.exe, create file expdat.dmp and so on. I choose to export only tables and there I must write which ones. Is there any chance of getting all of them? thanks

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  • Is there a library / tool to query MySQL data files (MyISAM / InnoDB) without the server? (the SQLit

    - by MGW
    Oftentimes I want to query my MySQL data directly without a server running or without having access to the server (but having read / write rights to the files). Is there a tool or maybe even a library around to query MySQL data files like it is possible with SQLite? I'm specifically looking for InnoDB and MyISAM support. Performance is not a factor. I don't have any knowledge about MySQL internals, but I presume it should be possible to do and not too hard to get the specific code out? Thank you for any suggestions!

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  • Does normalization really hurt performance in high traffic sites?

    - by Luke101
    I am designing a database and I would like to normalize the database. I one query I will joining about 30-40 tables. Will this hurt the website performance if it ever becomes extremely popular? This will be the main query and it will be getting called 50% of the time. The other queries I will be joining about 2 tables. I have a choice right now to normalize or not to normalize but if the normalization becomes a problem in the future i may have to rewrite 40% of the software and it may take me a long time. Does normalization really hurt in this case? Should I denormalize now while I have the time?

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  • choose append to existing backup instead of overwrite

    - by aron
    Hello, I have a database and I made it's first backup 2 days ago. Then yesterday I spent an entire adding new records. This morning I ran a backup, (but I selected append to existing backup set) as pictured below. I just ran a restore and I found that it wiped out all my data from yesterday and it restored it from the backup of 2 days ago. Not the version from this mornings backup. I zipped this backup file to be safe. I changed some data in the DB, Then I ran the back up again, but this time I selected "overwrite all existing backup sets" Now when I restore the db it's seems to restore the data from the backup correctly. I think I learned a lesson here, correctly if I'm wrong My questions is, Did I lose an entire day of work? I still have this morning's backup .bak file safe in a zip. Is there anyway I can restore is with the right data?

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  • DB Interface Design Optimization: Is it better to optimise for Fewer requests of smaller data size?

    - by Overflow
    The prevailing wisdom in webservices/web requests in general is to design your api such that you use as few requests as possible, and that each request returns therefore as much data as is needed In database design, the accepted wisdom is to design your queries to minimise size over the network, as opposed to minimizing the number of queries. They are both remote calls, so what gives?

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  • What are the Limitations for Connecting to an Access Query in Excel

    - by thornomad
    I have an Access 2007 database that has a number of tables, some are fairly large (100,000+ records); I have created a union query to pull some of the same types of data from multiple tables into one large query for pivot table manipulation and reporting. For example: SELECT Language FROM Table1 UNION ALL SELECT Language FROM Table2 UNION ALL SELECT Language FROM Table3; This works. I found, quickly, however, that a union query will not show up when connecting to the datasource from Excel 2007. So, I created a second query to reference the union query. Like so: SELECT * FROM [The Above Union Query]; This query works and it, initially, was accessible from Excel. Time passed, I've added more data. Suddenly, when I connect to my Access database from Excel my query referencing the union has disappeared. MS Access shows no signs of an issue (data displays in Access) and my other non-union queries are showing up in Excel 2007 ... but not the one that references the union. What could be going on? Why did it disappear? I noticed if I switch some of the referenced tables in the union query to a smaller table (with less rows) all of sudden the query appears in Excel again. At least, I think that's what the difference is. I really can't put my finger on why some of the union queries won't show up and some will. Am stumped and need some guidance. Thanks.

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  • Using NULL in MySQL

    - by JPro
    The data in my dabatase comes from an external source and where ever there is no data passed, I keep NULL in those places. Can anyone tell me if there are any implications in using NULL to represent empty value? Should I follow some other convention like 'data_not_available'? or something like that? Can anyone suggest?

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  • get records from sqlite group by month

    - by peacmaker
    hi i hve an sqlite db which contain transactions each transaction has an price and has an transDate i want to retrieve the sum of the transaction group by month so the retrieved records should be like the following Price month 230 2 500 3 400 4 pleas any help

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  • PHP - Language Data

    - by bobrusha
    What's the best way to store language data? Keep it as variables in some kind of lang.php file... $l_ipsum = 'smth'; $l_rand = 'string'; Or select them from a database? I'm in search of your advice.

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  • How to do this query?

    - by Damiano
    Hello everybody! I have a mysql table with these columns: ID (auto-increment) ID_BOOK (int) PRICE (double) DATA (date) I know two ID_BOOK values, example, 1 and 2. QUERY: I have to extract all the PRICE (of the ID_BOOK=1 and ID_BOOK=2) where DATA is the same! Table example: 1 1 10.00 2010-05-16 2 1 11.00 2010-05-15 3 1 12.00 2010-05-14 4 2 18.00 2010-05-16 5 2 11.50 2010-05-15 Result example: 1 1 10.00 2010-05-16 4 2 18.00 2010-05-16 2 1 11.00 2010-05-15 5 2 11.50 2010-05-15 ID_BOOK=2 hasn't 2010-05-14 so i jump it. Thank you so much!

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  • Dynamic where clause in LINQ - with column names available at runtime

    - by sandesh247
    Disclaimer: I've solved the problem using Expressions from System.Linq.Expressions, but I'm still looking for a better/easier way. Consider the following situation : var query = from c in db.Customers where (c.ContactFirstName.Contains("BlackListed") || c.ContactLastName.Contains("BlackListed") || c.Address.Contains("BlackListed")) select c; The columns/attributes that need to be checked against the blacklisted term are only available to me at runtime. How do I generate this dynamic where clause? An additional complication is that the Queryable collection (db.Customers above) is typed to a Queryable of the base class of 'Customer' (say 'Person'), and therefore writing c.Address as above is not an option.

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  • Foreign Keys and Primary Keys at the same time

    - by Bader
    hello , i am trying to create table (orderdetails) , the table has two FKs and PKs at the same keys here is my code create table OrderDetails2 ( PFOrder_ID Number(3) PFProduct_ID Number(3) CONSTRAINT PF PRIMARY KEY (PFOrder_ID,PFProduct_ID), CONSTRAINT FK_1 FOREIGN KEY (PFProudct_ID) REFERENCES Product(Product_ID), CONSTRAINT FK_2 FOREIGN KEY (PFOrder_ID) REFERENCES Orderr(Order_ID) ); i am using Oracle express , a problem pops when i run the code , here is it ORA-00907: missing right parenthesis what is the problem ?

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  • Update with inner join ?

    - by phenevo
    I have two databases: DB1 and DB2 How to do something like: update myServer.DB1.dbo.hotels.Name = myServer.DB2.dbo.hotels.Name join myServer.DB2.dbo.hotels on myServer.DB2.dbo.hotels.Code= myServer.DB1.dbo.hotels.Code where myServer.DB2.dbo.hotels.CountryCoe != myServer.DB1.dbo.hotels.CountryCode

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  • Accessing an Access DB from Outlook via VBA

    - by camastanta
    Hi The situation: In Outlook I get a message from a server. The content of the message needs to be put into an Access db. But, there may not exist another message with the same date. So, I need to look into a db if there is already a message with the same date and time. If there exists one, then it needs to be replaced and otherwise the message needs to be added to the database. The database contains a list of current positions from the vehicles on the road. The problem: I have problems to compare a date time with a date time in an Access DB via VBA. The query I use returns no records but there is a record in the database. This is the query I use: adoRS.Open "SELECT * FROM currentpositions WHERE ((currentpositions. [dateLT])=" & "#" & date_from_message & "#" & ")", adoConn, adOpenStatic, adLockOptimistic Second I need to now what the result is of that query. How can I determine the number of records that my query gives me? Thanks camastanta

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