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• Database Modeling - Either/Or in Many-to-Many

  - by EkoostikMartin

  I have an either/or type of situation in a many-to-many relationship I'm trying to model. So I have these tables: Message ---- *MessageID MessageText Employee ---- *EmployeeID EmployeeName Team ---- *TeamID TeamName MessageTarget ---- MessageID EmployeeID (nullable) TeamID (nullable) So, a Message can have either a list of Employees, or a list of Teams as a MessageTarget. Is the MessageTarget table I have above the best way to implement this relationship? What constraints can I place on the MessageTarget effectively? How should I create a primary key on MessageTarget table?

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• Using PHP variables inside SQL statements?

  - by Homer

  For some reason I can't pass a var inside a mysql statement. I have a function that can be used for multiple tables. So instead of repeating the code I want to change the table that is selected from like so, function show_all_records($table_name) { mysql_query("SELECT * FROM $table_name"); etc, etc... } And to call the function I use show_all_records("some_table") or show_all_records("some_other_table") depending on which table I want to select from at the moment. But it's not working, is this because variables can't be passed through mysql statements?

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• NoSql Crash Course/Tutorial

  - by Chris Thompson

  Hi all, I've seen NoSQL pop up quite a bit on SO and I have a solid understanding of why you would use it (from here, Wikipedia, etc). This could be due to the lack of concrete and uniform definition of what it is (more of a paradigm than concrete implementation), but I'm struggling to wrap my head around how I would go about designing a system that would use it or how I would implement it in my system. I'm really stuck in a relational-db mindset thinking of things in terms of tables and joins... At any rate, does anybody know of a crash course/tutorial on a system that would use it (kind of a "hello world" for a NoSQL-based system) or a tutorial that takes an existing "Hello World" app based on SQL and converts it to NoSQL (not necessarily in code, but just a high-level explanation). I see this having one solid answer, but if you guys feel like it should be community wiki, I'll be happy to change it. Thanks! Chris

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• SQL Table Setup Advice

  - by Ozzy

  Hi all. Basically I have an xml feed from an offsite server. The xml feed has one parameter ?value=n now N can only be between 1 and 30 What ever value i pick, there will always be 4000 rows returned from the XML file. My script will call this xml file 30 times for each value once a day. So thats 120000 rows. I will be doing quite complicated queries on these rows. But the main thing is I will always filter by value first so SELECT * WHERE value = 'N' etc. That will ALWAYS be used. Now is it better to have one table where all 120k rows are stored? or 30 tables were 4k rows are stored? EDIT: the SQL database in question will be MySQL

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• Best way to implement keywords for image upload gallery

  - by Dan Berlyoung

  I'm starting to spec out an image gallery type system similar to Facebook's. Members of the site will be able to create image galleries and upload images for others to view. Images will have keywords the the uploader can specify. Here's the question, what's the best way to model this? With image and keyword tables linked vi a HABTM relation? Or a single image table with the keywords saved as comma delimited values in a text field in the image record? Then search them using a LIKE or FULL TEXT index function? I want to be able to pull up all images containing a given keyword as well as generate a keyword cloud. I'm leaning toward the HABTM setup but I wanted to see what everyone else though. Thanks!!

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• How to add Transactions with a DataSet created using the Add Connection Wizard?

  - by RoguePlanetoid

  I have a DataSet that I have added to my project where I can Insert and Add records using the Add Query function in Visual Studio 2010, however I want to add transactions to this, I have found a few examples but cannot seem to find one that works with these. I know I need to use the SQLClient.SQLTransaction Class somehow. I used the Add New Data Source Wizard and added the Tables/View/Functions I need, I just need an example using this process such as How to get the DataConnection my DataSet has used. Assuming all options have been set in the wizard and I am only using the pre-defined adapters and options asked for in this wizard, how to I add the Transaction logic to my Database. For example I have a DataSet called ProductDataSet with the XSD created for this, I have then added my Stock table as a Datasource and Added an AddStock method with a wizard, this also if a new item calls an AddItem method, if either of these fails I want to rollback the AddItem and AddStock in this case.

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• sql query question

  - by bu0489

  hey guys, just having a bit of difficulty with a query, i'm trying to figure out how to show the most popular naturopath that has been visited in a centre. My tables look as follows; Patient(patientId, name, gender, DoB, address, state,postcode, homePhone, businessPhone, maritalStatus, occupation, duration,unit, race, registrationDate , GPNo, NaturopathNo) and Naturopath (NaturopathNo, name, contactNo, officeStartTime, officeEndTime, emailAddress) now to query this i've come up with SELECT count(*), naturopathno FROM dbf10.patient WHERE naturopathno != 'NULL' GROUP BY naturopathno; which results in; COUNT(*) NATUROPATH 2 NP5 1 NP6 3 NP2 1 NP1 2 NP3 1 NP7 2 NP8 My question is, how would I go about selecting the highest count from this list, and printing that value with the naturopaths name? Any suggestions are very welcome, Brad

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• Converting DAO to ADO

  - by webworm

  I am working with an Access 2003 database that has a subroutine using DAO code. This code loops through the table definitions and refreshes the ODBC connection string. I would like to convert this to ADO so I do not have to reference the DAO object library. Here is the code ... Public Sub RefreshODBCLinks(newConnectionString As String) Dim db As DAO.Database Dim tb As DAO.TableDef Set db = CurrentDb For Each tb In db.TableDefs If Left(tb.Connect, 4) = "ODBC" Then tb.Connect = newConnectionString tb.RefreshLink Debug.Print "Refreshed ODBC table " & tb.Name End If Next tb Set db = Nothing MsgBox "New connection string is " & newConnectionString, vbOKOnly, "ODBC Links refreshed" End Sub The part I am unsure of is how to loop through the tables and get/set their connection strings.

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• SQLServer triggers

  - by Evl-ntnt

  Please help me to write trigger that, adds new rows in table I have 3 tables in my database. 1) Regions (id, name); id - primary 2) Technics (id, name); id - primary 3) Availability (id, region, technic, count); id - primary, region - foreign on Regions.id, Technik - foreign on technics.id I want to add new row in Availability for each Technics row on adding row in Regions. Somethink like: procedure void OnAddNewRegion(int region) { foreach (Row r in Technic) { Availability.Rows.Add(new Row(id, region, r.Id, 0)); } } But in SQL trigger. Same I want to do on the adding new Technics row

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• Query to return internal details about stored function in SQL Server database

  - by Anthony

  I have been given access to a SQL Server database that is currently used by 3rd party app. As such, I don't have any documentation on how that application stores the data or how it retrieves it. I can figure a few things out based on the names of various tables and the parameters that the user-defined functions takes and returns, but I'm still getting errors at every other turn. I was thinking that it would be really helpful if I could see what the stored functions were doing with the parameters given to return the output. Right now all I've been able to figure out is how to query for the input parameters and the output columns. Is there any built-in information_schema table that will expose what the function is doing between input and output?

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• Weighted Average with LINQ

  - by jsmith

  My goal is to get a weighted average from one table, based on another tables primary key. Example Data: Table1 Key WEIGHTED_AVERAGE 0200 0 Table2 ForeignKey LENGTH PCR 0200 105 52 0200 105 60 0200 105 54 0200 105 -1 0200 47 55 I need to get a weighted average based on the length of a segment and I need to ignore values of -1. I know how to do this in SQL, but my goal is to do this in LINQ. It looks something like this in SQL: SELECT Sum(t2.PCR*t2.LENGTH)/Sum(t2.LENGTH) AS WEIGHTED_AVERAGE FROM Table1 t1, Table2 t2 WHERE t2.PCR <> -1 AND t2.ForeinKey = t1.Key; I am still pretty new to LINQ, and having a hard time figuring out how I would translate this. The result weighted average should come out to roughly 55.3. Thank you.

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• Synchronising local and remote DB

  - by nico

  Hi everyone, I have a general question about DB synchronisation. So, I'm developing a website locally (PHP + MySQL) and I would like to be able to synchronise at least the structure (and maybe the contents) of the two DB when one of the two is changed (normally I would change the local copy). Right now what I'm doing is to use mysqldump to dump the modified tables and then import them in the remote DB or do it by hand if the changes are minimal. However I find this tedious and error-prone. For the PHP I'm currently using Quanta+ which has the handy feature of finding files that have changed and just upload those. Is there something similar for MySQL? Otherwise how do you keep your DBs synchronised? Thanks nico PS: I'm sorry if this was already asked, I saw other questions that deal with similar topics, but couldn't really find an answer.

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• SQL Server ORDER BY/WHERE with nested select

  - by Echilon

  I'm trying to get SQL Server to order by a column from a nested select. I know this isn't the best way of doing this but it needs to be done. I have two tables, Bookings and BookingItems. BookingItems contains StartDate and EndDate fields, and there can be multiple BookingItems on a Booking. I need to find the earliest startdate and latest end date from BookingItems, then filter and sort by these values. I've tried with a nested select, but when I try to use one of the selected columns in a WHERE or ORDER BY, I get an "Invalid Column Name". SELECT b.*, (SELECT COUNT(*) FROM bookingitems i WHERE b.BookingID = i.BookingID) AS TotalRooms, (SELECT MIN(i.StartDate) FROM bookingitems i WHERE b.BookingID = i.BookingID) AS StartDate, (SELECT MAX(i.EndDate) FROM bookingitems i WHERE b.BookingID = i.BookingID) AS EndDate FROM bookings b LEFT JOIN customers c ON b.CustomerID = c.CustomerID WHERE StartDate >= '2010-01-01' Am I missing something about SQL ordering? I'm using SQL Server 2008.

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• Importing/Exporting Relationships in MS Access

  - by lamcro

  I have a couple of mdb files with the exact table structure. I have to change the primary key of the main table from autonumber to number in all of them, which means I have to: Drop the all the relationships the main table has Change the main table Create the relationships again,... for all the tables. Is there any way to export the relationships from one file and importing them to all the rest? I am sure this can be done with some macro/vb code. Does anyone has an example I could use? Thanks.

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• Using memtables in sql. When is it reasonable and is it safe?

  - by Spiros

  I was just reading an update from a friend's project, mentioning the use of memtables to store data temporatily and then flush to a table on disk. Up to now, I have never faced a situation where I would use a memtable, or a situation where I would think the use of a mem table would be beneficial; so I wonder, when would someone use mem tables? what makes a memtable (appart from access speed) a reasonable choice? and how safe is it, even for temp data? there is always the limitation of available physical memory.

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• In Elixir or SQLAlchemy, is there a way to also store a comment for a/each field in my entities?

  - by kchau

  Our project is basically a web interface to several systems of record. We have many tables mapped, and the names of each column aren't as well named and intuitive as we'd like... The users would like to know what data fields are available (i.e. what's been mapped from the database). But, it's pointless to just give them column names like: USER_REF1, USER_REF2, etc. So, I was wondering, is there a way to provide a comment in the declaration of my field? E.g. class SegregationCode(Entity): using_options(tablename="SEGREGATION_CODES") segCode = Field(String(20), colname="CODE", ... primary_key=True) #Have a comment attr too? If not, any suggestions?

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• Linq query with subquery as comma-separated values

  - by Keith

  In my application, a company can have many employees and each employee may have have multiple email addresses. The database schema relates the tables like this: Company - CompanyEmployeeXref - Employee - EmployeeAddressXref - Email I am using Entity Framework and I want to create a LINQ query that returns the name of the company and a comma-separated list of it's employee's email addresses. Here is the query I am attempting: from c in Company join ex in CompanyEmployeeXref on c.Id equals ex.CompanyId join e in Employee on ex.EmployeeId equals e.Id join ax in EmployeeAddressXref on e.Id equals ax.EmployeeId join a in Address on ax.AddressId equals a.Id select new { c.Name, a.Email.Aggregate(x=x + ",") } Desired Output: "Company1", "[email protected],[email protected],[email protected]" "Company2", "[email protected],[email protected],[email protected]" ... I know this code is wrong, I think I'm missing a group by, but it illustrates the point. I'm not sure of the syntax. Is this even possible? Thanks for any help.

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• SQL Server 2008 automated database drop, create and fill

  - by lox

  For the database in my project I have a drop/create script for the database, a script for creating tables and SPs and an Access 2003 .mdb file with some exported values. To set up the database from scratch I can use my SQL management studio to first run one script, then the other and lastly manually run the sort of tedious import task. But I would like to do this as automated as possible. Hopefully something like putting the three files in a folder along with a fourth script to execute. Looking something like: run script "dropcreate.sql" run script "createtables.sql" import "values.mdb" How is this done? I hope to avoid using SSIS and the like. The tricky this is of course the import of data, where I can't seem to find a simple way. It is also important that the files a left as they are and not embedded into anything.

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• Creating a proper CMS thoughts

  - by dallasclark

  I'm just about to expand the functionality of our own CMS but was thinking of restructuring the database to make it simpler to add/edit data types and values. Currently, the CMS is quite flat - the CMS requires a field in the database for every type of stored value. The first option that comes to mind is simply a table which keeps the data types (ie: Address 1, Suburb, Email Address etc) and another table which holds values for each of these data types. Just like how Wordpress keeps values in the 'options' table, serialize would be used to store an array of values. The second option is how Drupal works, the CMS creates tables for every data type. Unlike Wordpress, this can be a bit of an overkill but really useful for SQL queries when ordering and grouping by a particular value. What's everyone's thoughts?

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• Join Query Help

  - by John

  Hello, The query below works well. It pulls data from two MySQL tables, "submission" and "login." I would like to also pull data from a third table called "comment" in the same database. The table "comment" has the following fields: commentid, loginid, submissionid, comment, datecommented Two of the fields in the table "login" are called "loginid" and "username." In the query below, I would like to count all "commentid" in "comment" where "loginid" equals the "loginid" in "login" where "username" equals "$profile." How can I do this? Thanks in advance, John $sqlStr1 = "SELECT l.username, l.loginid, s.loginid, s.submissionid, s.title, s.url, s.datesubmitted, s.displayurl, l.created, count(s.submissionid) countSubmissions FROM submission AS s INNER JOIN login AS l ON s.loginid = l.loginid WHERE l.username = '$profile'";

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• Sphinx non-fulltext, integer only search

  - by James

  Hello guys, I've got a few tables that literally only hold integers, no "words" and for some reason Sphinx is unable to hold this data in it's library. Just returns "0 bytes" errors for these indexes. Is it possible to do this? If so, how? Below is an example from my Sphinx.conf for one that fails. source track { type = mysql sql_host = host sql_user = user sql_pass = pass sql_db = db sql_port = port sql_query = SELECT id, user, time FROM track; sql_attr_uint = user sql_attr_uint = time sql_query_info = SELECT * FROM track WHERE id=$id } index track { source = track path = /var/lib/sphinx/track docinfo = extern charset_type = utf-8 min_prefix_len = 1 enable_star = 1 }

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• Core Data Relationships in pre-populated SQLite database

  - by Cardinal

  Hi All, I'm new to Core Data. Currently I have following tables on hand: tbl_teahcer tbl_student tbl_course tbl_student_course_map ----------- ----------- ---------- ---------------------- teacher_id student_id course_id student_id name name name course_id teahcer_id And I'm going to make the xcdatamodel as below: Course Teacher ------ ------- name name teacher <<----------> courses students <<---| | Student | ------- | name |----->> courses My questions are as follows: As I'd like to create TableView for Cource Entity, is it a must to create the Inverse Relationship from Teacher to Course, and Student to Course? What is the beneit for having the Inverse Relationship? I got some pre-defined data on hand, and I'd like to create a SQLite storage for pre-populated source. How can I set up the relationships (both directions) in SQLite? Thank you for your help! Regards, Cardinal

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• Preview result of update/insert query whithout comitting changes to database in MySQL?

  - by Camsoft

  I am writing a script to import CSV files into existing tables within my database. I decided to do the insert/update operations myself using PHP and INSERT/UPDATE statements, and not use MySQL's LOAD INFILE command, I have good reasons for this. What I would like to do is emulate the insert/update operations and display the results to the user, and then give them the option of confirming that this is OK, and then committing the changes to the database. I'm using InnoDB database engine with support for transactions. Not sure if this helps but was thinking down the line of insert/update, query data, display to user, then either commit or rollback transaction? Any advise would be appreciated.

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• Virtual Function Implementation

  - by Gokul

  Hi, I have kept hearing this statement. Switch..Case is Evil for code maintenance, but it provides better performance(since compiler can inline stuffs etc..). Virtual functions are very good for code maintenance, but they incur a performance penalty of two pointer indirections. Say i have a base class with 2 subclasses(X and Y) and one virtual function, so there will be two virtual tables. The object has a pointer, based on which it will choose a virtual table. So for the compiler, it is more like switch( object's function ptr ) { case 0x....: X->call(); break; case 0x....: Y->call(); }; So why should virtual function cost more, if it can get implemented this way, as the compiler can do the same in-lining and other stuff here. Or explain me, why is it decided not to implement the virtual function execution in this way? Thanks, Gokul.

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• Entity Framework doesn't like 0..1 to * relationships.

  - by Orion Adrian

  I have a database framework where I have two tables. The first table has a single column that is an identity and primary key. The second table contains two columns. One is a nvarchar primary key and the other is a nullable foreign key to the first table. On the default import of the database I get the following error: Condition cannot be specified for Column member 'ForeignKeyId' because it is marked with a 'Computed' or 'Identity' StoreGeneratedPattern. where ForeignKeyId is the second foreign key reference in the second table. Is this just something the entity model doesn't do? Or am I missing something?

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