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  • Two different definitions of database schema

    - by AspOnMyNet
    a) I found two definitions of schema: FIRST - A set of information that describes a table is known as a schema, and schemas are used to describe specific tables within a database, as well as entire databases (and the relationship between tables in them, if any). SECOND - A database schema is a way to logically group objects such as tables, views, stored procedures etc. Think of a schema as a container of objects. I assume the two descriptions describe entirely different concepts, which just happen to use the same name? b) A database schema is a way to logically group objects such as tables, views, stored procedures etc. Think of a schema as a container of objects. If I understand the above definition correctly, then database schema is similar to a namespace, only difference being that we can assign access permissions to database schema, while same can’t be done with namespaces? thanx

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  • which is better, creating a materialized view or a new table?

    - by Carson
    I have some demanding mysql queries that are needed to grap same up-to-date datasets from 5-7 mysql tables. I am thinking of creating a table or materialized view to gather all demanding columns from other tables, so as to increase performance. If I create that table, I may need to do extra insert / update / delete operation each time other tables updated. if I create materialized view, I am worrying if the performance can be greatly improved. Because data from other tables are changing very frequently. Most likely, the view may need to be created first everytime before selecting it. Any ideas? e.g. how to cache? other extra measures I can do?

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  • How can i test my DB speed? (Learning)

    - by acidzombie24
    I have design a database. Theres no columns with indexing, nor any code for optimizing. I am positive i should index certain columns since i search them a lot. My question is HOW do i test if any part of my database will be slow? ATM I am using sqlite and i will be switching to either MS Sql or MySql based on my host provider. Will creating 100,000 records in each table be enough? Or will that always be fast in sqlite and i need to do 1mil? Do i need 10mil before a database will become slow? Also how do i time it? I am using C# so should i use StopWatch or is there a ADO.NET/Sqlite function i should use?

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  • XSD problem: The value of attribute on element is not valid with respect to its type

    - by Tom Brito
    (First of all, I'm trying to learn how to handle xsd files, I know very little) I got this xsd, and just copy to Eclipse IDE, and it says there an error on line 26: <xs:element name="Issuer" type="dkx:IssuerType" /> saying: cvc-attribute.3: The value 'dkx:IssuerType' of attribute 'type' on element 'xs:element' is not valid with respect to its type, 'QName'. Any idea what is this? (as this is an example file, I'm assuming it is an independent file, hope it is)

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  • which is better, creating a view or a new table?

    - by Carson
    I have some demanding mysql queries that are needed to grap same datasets from several mysql tables. I am thinking of creating a table or view to gather all demanding columns from other tables, so as to increase performance. If I create that table, I may need to do extra insert / update / delete operation each time other tables updated. if I create view, I am worrying if the performance can be greatly improved. Because data from other tables are changing very frequently. Most likely, the view may need to be created first everytime before selecting it. Any ideas? e.g. how to cache? other extra measures I can do?

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  • Zend DB inserting relational data

    - by Wimbjorno
    I'm using the Zend Framework database relationships for a couple of weeks now. My first impression is pretty good, but I do have a question related to inserting related data into multiple tables. For a little test application I've related two tables with each other by using a fuse table. +---------------+ +---------------+ +---------------+ | Pages | | Fuse | | Prints | +---------------+ +---------------+ +---------------+ | pageid | | fuseid | | printid | | page_active | | fuse_page | | print_title | | page_author | | fuse_print | | print_content | | page_created | | fuse_locale | | ... | | ... | | ... | +---------------+ +---------------+ +---------------+ Above is an example of my DB architecture Now, my problem is how to insert related data to two separate tables and insert the two newly created ID's into the fuse table at the same time. If someone could could maybe explain or give me a topic related tutorial. I would appreciate it!

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  • NHibernate SchemaUpdate adding existing foreign keys again?

    - by afsharm
    I'm using SchemaUpdate to synchronize my hbms with existing database. Database has recently created based on hbms and is completely up-to-date. But SchemaUpdate generates all foreign key constraints again. For example suppose you have Student and Teacher. Student has association to Teacher with name ArtTeacher. ArtTeacher is a foreign key from Student to Teacher. Suppose database is up-to-date and currently holde Student, Teacher and their foreign key relation. So HBM and Database are equivalent. Know SchemaUpdate must not do anything but when I see its generated scripts, it re-produce that foreign key again. Why this happens? Is there any way to avoid it?

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  • Android From Local DB (DAO) to Server sync (JSON) - Design issue

    - by Taiko
    I sync data between my local DB and a Server. I'm looking for the cleanest way to modelise all of this. I have a com.something.db package That contains a Data Helper and couple of DAO classes that represents objects stored in the db (I didn't write that part) com.something.db --public DataHelper --public Employee @DatabaseField e.g. "name" will be an actual column name in the DB -name @DatabaseField -salary etc... (all in all 50 fields) I have a com.something.sync package That contains all the implementation detail on how to send data to the server. It boils down to a ConnectionManager that is fed by different classes that implements a 'Request' interface com.something.sync --public interface ConnectionManager --package ConnectionManagerImpl --public interface Request --package LoginRequest --package GetEmployeesRequest My issue is, at some point in the sync process, I have to JSONise and de-JSONise my data (E.g. the Employee class). But I really don't feel like having the same Employee class be responsible for both his JSONisation and his actual representation inside the local database. It really doesn't feel right, because I carefully decoupled the rest, I am only stuck on this JSON thing. What should I do ? Should I write 3 Employee classes ? EmployeeDB @DatabaseField e.g. "name" will be an actual column name in the DB -name @DatabaseField -salary -etc... 50 fields EmployeeInterface -getName -getSalary -etc... 50 fields EmployeeJSON -JSON_KEY_NAME = "name" The JSON key happens to be the same as the table name, but it isn't requirement -name -JSON_KEY_SALARY = "salary" -salary -etc... 50 fields It feels like a lot of duplicates. Is there a common pattern I can use there ?

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  • The C++ Standard Template Library as a BDB Database (part 1)

    - by Gregory Burd
    If you've used C++ you undoubtedly have used the Standard Template Libraries. Designed for in-memory management of data and collections of data this is a core aspect of all C++ programs. Berkeley DB is a database library with a variety of APIs designed to ease development, one of those APIs extends and makes use of the STL for persistent, transactional data storage. dbstl is an STL standard compatible API for Berkeley DB. You can make use of Berkeley DB via this API as if you are using C++ STL classes, and still make full use of Berkeley DB features. Being an STL library backed by a database, there are some important and useful features that dbstl can provide, while the C++ STL library can't. The following are a few typical use cases to use the dbstl extensions to the C++ STL for data storage. When data exceeds available physical memory.Berkeley DB dbstl can vastly improve performance when managing a dataset which is larger than available memory. Performance suffers when the data can't reside in memory because the OS is forced to use virtual memory and swap pages of memory to disk. Switching to BDB's dbstl improves performance while allowing you to keep using STL containers. When you need concurrent access to C++ STL containers.Few existing C++ STL implementations support concurrent access (create/read/update/delete) within a container, at best you'll find support for accessing different containers of the same type concurrently. With the Berkeley DB dbstl implementation you can concurrently access your data from multiple threads or processes with confidence in the outcome. When your objects are your database.You want to have object persistence in your application, and store objects in a database, and use the objects across different runs of your application without having to translate them to/from SQL. The dbstl is capable of storing complicated objects, even those not located on a continous chunk of memory space, directly to disk without any unnecessary overhead. These are a few reasons why you should consider using Berkeley DB's C++ STL support for your embedded database application. In the next few blog posts I'll show you a few examples of this approach, it's easy to use and easy to learn.

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  • SQL SERVER – Get Schema Name from Object ID using OBJECT_SCHEMA_NAME

    - by pinaldave
    Sometime a simple solution have even simpler solutions but we often do not practice it as we do not see value in it or find it useful. Well, today’s blog post is also about something which I have seen not practiced much in codes. We are so much comfortable with alternative usage that we do not feel like switching how we query the data. I was going over forums and I noticed that at one place user has used following code to get Schema Name from ObjectID. USE AdventureWorks2012 GO SELECT s.name AS SchemaName, t.name AS TableName, s.schema_id, t.OBJECT_ID FROM sys.Tables t INNER JOIN sys.schemas s ON s.schema_id = t.schema_id WHERE t.name = OBJECT_NAME(46623209) GO Before I continue let me say I do not see anything wrong with this script. It is just fine and one of the way to get SchemaName from Object ID. However, I have been using function OBJECT_SCHEMA_NAME to get the schema name. If I have to write the same code from the beginning I would have written the same code as following. SELECT OBJECT_SCHEMA_NAME(46623209) AS SchemaName, t.name AS TableName, t.schema_id, t.OBJECT_ID FROM sys.tables t WHERE t.name = OBJECT_NAME(46623209) GO Now, both of the above code give you exact same result. If you remove the WHERE condition it will give you information of all the tables of the database. Now the question is which one is better – honestly – it is not about one is better than other. Use the one which you prefer to use. I prefer to use second one as it requires less typing. Let me ask you the same question to you – which method to get schema name do yo use? and Why? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL System Table, SQL Tips and Tricks, T SQL, Technology

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  • BizTalk 2009 - Error when Testing Map with Flat File Source Schema

    - by StuartBrierley
    I have recently been creating some flat file schemas using the BizTalk Server 2009 Flat File Schema Wizard.  I have then been mapping these flat file schemas to a "normal" xml schema format. I have not previsouly had any cause to map flat files and ran into some trouble when testing the first of these flat file maps; with an instance of the flat file as the source it threw an XSL transform error: Test Map.btm: error btm1050: XSL transform error: Unable to write output instance to the following <file:///C:\Documents and Settings\sbrierley\Local Settings\Temp\_MapData\Test Mapping\Test Map_output.xml>. Data at the root level is invalid. Line 1, position 1. Due to the complexity of the map in question I decided to created a small test map using the same source and destination schemas to see if I could pinpoint the problem.  Although the source message instance vaildated correctly against the flat file schema, when I then tested this simplified map I got the same error. After a time of fruitless head scratching and some serious google time I figured out what the problem was. Looking at the map properties I noticed that I had the test map input set to "XML" - for a flat file instance this should be set to "native".

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  • row specific class

    - by stimpie
    How do I create a Zend_Db_Table which returns a different class for each row.? Example UserTable has id,name and type Type contains class names (admin,client,etc...) The classes admin, client are all subclasses of user If I call fetch I need to get a admin or client object depending on the corresponding value in the db.

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  • How to write a subquery using DB

    - by Rita
    SELECT SUM( amount_disbursed ) disbusedamount, (select SUM( loaninstallmentpaid_amount ) FROM ourbank_loan_repayment) paidamount, SUM( amount_disbursed )- (select SUM( loaninstallmentpaid_amount ) FROM ourbank_loan_repayment) differenceamount FROM ourbank_loan_disbursement Any Help would be appreciated

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  • Synchronising scripts / db / files from dev system to web server

    - by Spoonface
    I work as a freelance web dev, and up until now have been ftping my scripts / databases / static files to my web server manually, but I'm finding that is too error prone. So I'm looking for an app to automate uploading new and updated scripts / files / databases / etc. I know a lot of independent devs use WinSCP or Unison, but I don't think those apps can synch databases. Does anyone have any other suggestions? It doesn't need to be anything overly feature rich as I'm not working within a team or across multiple operating systems or anything like that. I can purchase any reasonably priced license if necesary. My work is primarily for PHP / MySQL / Apache on a Windows system, and then uploaded to a Linux / Apache server. thanks for your time!

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  • Foreign key on table A --> B, AND foreign key on table B --> A. How is this done?

    - by unclaimedbaggage
    Hi, I have two tables - 'business' and 'business_contacts'. The business_contact table has a many-to-one relationship with the business table. Furthermore, each business has a 'primary contact' field - which I'd assume is a one-to-many relationship with the business_contacts table. The problem, of course, is that this creates a catch-22 for data insertion. Since neither field can be null, I can't insert a business_contact until I have a corresponding business, but I can't insert a business until I have a corresponding business_contact. If anyone could help me get my head around how mutual one-to-many relationships are supposed to be dealt with I'd be most appreciative. (Project being done in MySQL if it makes any difference)

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  • Zend Framework Db Select Join table help

    - by tester2001
    I have this query: SELECT g.title, g.asin, g.platform_id, r.rank FROM games g INNER JOIN ranks r ON ( g.id = r.game_id ) ORDER BY r.rank DESC LIMIT 5` Now, this is my JOIN using Zend_Db_Select but it gives me array error $query = $this-select(); $query-from(array('g' = 'games'), array()); $query-join(array('r' = 'ranks'), 'g.id = r.game_id', array('g.title', 'g.asin', 'g.platform_id', 'r.rank')); $query-order('r.rank DESC'); $query-limit($top); $resultRows = $this-fetchAll($query); return $resultRows; Anyone know what I could be doing wrong? I want to get all the columns in 'games' to show and the 'rank' column in the ranks table.

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  • servlet connection to DB

    - by underW
    Initially, after reading books on the subject, I firmly believed that the algorithm for working with a database from a servlet is as follows: create a connection - connect to the database - form a request - send the request to the database - get the query results - process them - close connection - OK. Now, with a better understanding of the practical side, I realized that nobody does it that way, and everything happens through a connection pool according to the following algorithm: initialize the servlet - create a connection pool - a request comes from a user - take a free connection from the pool - form a request - send the request to the database - get the query results - process them - return the connection back to the pool - ok. Now I have this problem: We have 100 users, they are divided into 10 groups, each group has it's own username and password to connect to the database. Moreover, each group may have different rights to the database. How am I supposed to use a connection pool in this situation? If I understand correctly, a pool is nothing more than just a group of similar connections with a single login and password. And here I have 10 pairs of username / password. It looks like I cannot use the pool in this situation. What should I do?

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  • Berkeley DB tuple with unknown datatype

    - by Ronnie
    I'm working with a Berkeley database (in Java). I need to read a tuple where the sequence is a string, either an int or long, then another string. How can I determine if the tuple holds an int or a long? Depending on what the tuple holds, I'll do one of the following: String s1 = input.readString(); int num1 = input.readInt(); String s2= input.readString(); or String s1 = input.readString(); long num1 = input.readLong(); String s2= input.readString(); The int is 4 bytes and the long is 8 bytes. If the tuple holds an int and I read it in as a long, I get an invalid value as it converts the 4 byte int + 4 bytes of the following string into a long.

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  • Schema-less design guidelines for Google App Engine Datastore and other NoSQL DBs

    - by jamesaharvey
    Coming from a relational database background, as I'm sure many others are, I'm looking for some solid guidelines for setting up / designing my datastore on Google App Engine. Are there any good rules of thumb people have for setting up these kinds of schema-less data stores? I understand some of the basics such as denormalizing since you can't do joins, but I was wondering what other recommendations people had. The particular simple example I am working with concerns storing searches and their results. For example I have the following 2 models defined in my Google App Engine app using Python: class Search(db.Model): who = db.StringProperty() what = db.StringProperty() where = db.StringProperty() createDate = db.DateTimeProperty(auto_now_add=True) class SearchResult(db.Model): title = db.StringProperty() content = db.StringProperty() who = db.StringProperty() what = db.StringProperty() where = db.StringProperty() createDate = db.DateTimeProperty(auto_now_add=True) I'm duplicating a bunch of properties between the models for the sake of denormalization since I can't join Search and SearchResult together. Does this make sense? Or should I store a search ID in the SearchResult model and effectively 'join' the 2 models in code when I retrieve them from the datastore? Please keep in mind that this is a simple example. Both models will have a lot more properties and the way I'm approaching this right now, I would put any property I put in the Search model in the SearchResult model as well.

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  • XML Schema: How to specify an attribute with a custom 'simpleType' type?

    - by mackenir
    In my XML schema definition, I'm trying to restrict the value of an attribute to be an integer between 0 and 100. With reference to the sample schema below, I want attribute 'attr' on element 'root' to have this restriction. To achieve this I define a simpleType 'Percentage' and set this as the 'type' of 'attr'. However, my XML schema editor (VS 2008) flags the attribute up as having a problem: "Type 'Percentage' is not declared or is not a simple type". <?xml version="1.0" encoding="utf-8"?> <xs:schema elementFormDefault="qualified" id="test" xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://testtttt"> <xs:simpleType name="Percentage"> <xs:restriction base="xs:integer"> <xs:minInclusive value="0"/> <xs:maxInclusive value="100"/> </xs:restriction> </xs:simpleType> <xs:element name="root"> <xs:complexType> <xs:attribute name="attr" type="Percentage" use="optional" /> </xs:complexType> </xs:element>

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  • Designing persistence schema for BigTable on AppEngine

    - by Vitalij Zadneprovskij
    I have tried to design the datastore schema for a very small application. That schema would have been very simple, if not trivial, using a relational database with foreign keys, many-to-many relations, joins, etc. But the problem was that my application was targeted for Google App Engine and I had to design for a database that was not relational. At the end I gave up. Is there a book or an article that describes design principles for applications that are meant for such databases? The books that I have found are about programming for App Engine and they don't spend many words about database design principles.

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  • How can I restore a corrupted Shotwell db?

    - by Yann Dìnendal
    While I was importing photos from a SD card in Shotwell, my laptop has crashed (shutdown because of over-heating). Now, I can no longer launch Shotwell: $ shotwell ** ERROR:x86_64-linux-gnu/db/VersionTable.c:104:version_table_construct: assertion failed: (res == SQLITE_OK) If I move the .db file ~/.shotwell/data/photo.db elsewhere so it is no longer present (but backed-up), shotwell will launch, but will rebuild its library, which will be empty. I can re-import the folders shotwell creates, but I lose nearly all meta-data (most importantly the "folders", or events, and their main picture) Is there a way to repair/rebuild/restore photo.db? How can I see what's inside? how bad it's damaged? Or is there another way to get back my events and imports?

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