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  • Circular database relationships. Good, Bad, Exceptions?

    - by jim
    I have been putting off developing this part of my app for sometime purely because I want to do this in a circular way but get the feeling its a bad idea from what I remember my lecturers telling me back in school. I have a design for an order system, ignoring the everything that doesn't pertain to this example I'm left with: CreditCard Customer Order I want it so that, Customers can have credit cards (0-n) Customers have orders (1-n) Orders have one customer(1-1) Orders have one credit card(1-1) Credit cards can have one customer(1-1) (unique ids so we can ignore uniqueness of cc number, husband/wife may share cc instances ect) Basically the last part is where the issue shows up, sometimes credit cards are declined and they wish to use a different one, this needs to update which their 'current' card is but this can only change the current card used for that order, not the other orders the customer may have on disk. Effectively this creates a circular design between the three tables. Possible solutions: Either Create the circular design, give references: cc ref to order, customer ref to cc customer ref to order or customer ref to cc customer ref to order create new table that references all three table ids and put unique on the order so that only one cc may be current to that order at any time Essentially both model the same design but translate differently, I am liking the latter option best at this point in time because it seems less circular and more central. (If that even makes sense) My questions are, What if any are the pros and cons of each? What is the pitfalls of circular relationships/dependancies? Is this a valid exception to the rule? Is there any reason I should pick the former over the latter? Thanks and let me know if there is anything you need clarified/explained. --Update/Edit-- I have noticed an error in the requirements I stated. Basically dropped the ball when trying to simplify things for SO. There is another table there for Payments which adds another layer. The catch, Orders can have multiple payments, with the possibility of using different credit cards. (if you really want to know even other forms of payment). Stating this here because I think the underlying issue is still the same and this only really adds another layer of complexity.

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  • Sorting string column containing numbers in SQL?

    - by Ish
    Dear Folks, I am trying to sort string column (containing numbers). // SELECT `name` FROM `mytable` ORDER BY `name` ASC +----------+ +-- name --+ +----------+ +-- a 1 ---+ +-- a 12 --+ +-- a 2 ---+ +-- a 3 ---+ You see natural sorting algorithm of Mysql is placing a 12 after a 1 (which is ok for most apps), But I have unique needs, so I want result should be sorted like this. +----------+ +-- name --+ +----------+ +-- a 1 ---+ +-- a 2 ---+ +-- a 3 ---+ +-- a 12 --+ Is it possible with just SQL, or I have to manipulate result-set at application level? Thanks for reading...

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  • codeIgniter: pass parameter to a select query from previous query

    - by krike
    I'm creating a little management tool for the browser game travian. So I select all the villages from the database and I want to display some content that's unique to each of the villages. But in order to query for those unique details I need to pass the id of the village. How should I do this? this is my code (controller): function members_area() { global $site_title; $this->load->model('membership_model'); if($this->membership_model->get_villages()) { $data['rows'] = $this->membership_model->get_villages(); $id = 1;//this should be dynamic, but how? if($this->membership_model->get_tasks($id)): $data['tasks'] = $this->membership_model->get_tasks($id); endif; } $data['title'] = $site_title." | Your account"; $data['main_content'] = 'account'; $this->load->view('template', $data); } and this is the 2 functions I'm using in the model: function get_villages() { $q = $this->db->get('villages'); if($q->num_rows() > 0) { foreach ($q->result() as $row) { $data[] = $row; } return $data; } } function get_tasks($id) { $this->db->select('name'); $this->db->from('tasks'); $this->db->where('villageid', $id); $q = $this->db->get(); if($q->num_rows() > 0) { foreach ($q->result() as $task) { $data[] = $task; } return $data; } } and of course the view: <?php foreach($rows as $r) : ?> <div class="village"> <h3><?php echo $r->name; ?></h3> <ul> <?php foreach($tasks as $task): ?> <li><?php echo $task->name; ?></li> <?php endforeach; ?> </ul> <?php echo anchor('site/add_village/'.$r->id.'', '+ add new task'); ?> </div> <?php endforeach; ?> ps: please do not remove the comment in the first block of code!

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  • MySQL not using index on DATE when used with '<' or '>' operators?

    - by Haroldo
    I'm using explain to test these queries. The col type is DATE this uses index: explain SELECT events.* FROM events WHERE events.date = '2010-06-11' this doesnt explain SELECT events.* FROM events WHERE events.date >= '2010-06-11' index as follows (phpmyadmin) Action Keyname Type Unique Packed Field Cardinality Collation Null Comment Edit Drop PRIMARY BTREE Yes No event_id 18 A Edit Drop date BTREE No No date 0 A i notice cardinality is 0, though there are some rows with the same date..

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  • Can I raise System Error in sql Server in a stored procedure.

    - by Shantanu Gupta
    I am writing a stored procedure where i m using try catch block. Now i have a unique column in a table. When i try to insert duplicate value it throws exception with exception no 2627. I want this to be done like this if (exists(select * from tblABC where col1='value')=true) raiseError(2627)--raise system error that would have thrown if i would have used insert query to insert duplicate value And which method will be better, using insert query or checking for duplicate value before insertion using Select query ?

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  • advance/basic and smartphone views in Rails

    - by aleds
    In a new Rail app I have to consider 2 differents user's type: basic and Advanced and I have to create smartphone views( unique view for both user's type). Then I have 3 view/layout: - web advance - web basic - smartphone I already have the adv/basic flag for the user, and I followed the RBates tutorial http://asciicasts.com/episodes/199-mobile-devices. What is the best way to manage the 3 views/layout ?

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  • Is there a way to find a specific file and then change into the directory containing it in one go?

    - by bergyman
    I'm looking for a way to find what I know will be a unique file, and then change into the directory containing that file. Something along the lines of: find . -name 'Subscription.java' | xargs cd Or: find . -name 'Subscription.java' -exec cd {} \; I know this won't work because it's both trying to cd supplying the entire absolute path, which contains the file, and also because xargs can't do any built in shell commands...but you get the point of what I want to accomplish.

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  • How to Auto-Increment Non-Primary Key? - SQL Server

    - by user311509
    CREATE TABLE SupplierQuote ( supplierQuoteID int identity (3504,2) CONSTRAINT supquoteid_pk PRIMARY KEY, PONumber int identity (9553,20) NOT NULL . . . CONSTRAINT ponumber_uq UNIQUE(PONumber) ); The above ddl produces an error: Msg 2744, Level 16, State 2, Line 1 Multiple identity columns specified for table 'SupplierQuote'. Only one identity column per table is allowed. How can i solve it? I want PONumber to be auto-incremented.

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  • Updating value in Linq to SQL IEnumerable

    - by Learner
    Using Linq to SQL: if(!parentlist.childlist.Contains(row1)) parentlist.childlist.Add(row1); else How do I update the required childlist row with row1? Each row of the child list has a unique id. parentlist implements IEnumerable and childlist is IList.

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  • Better alternative to autonumber primary keys

    - by Comrad_Durandal
    I am looking for a better primary key than the autonumber data type, namely for the reason that it's limited to a long integer, when I really just need the field to reflect a number or text string that will never ever repeat, no matter HOW many records are added or deleted from the table. The problem is I am not sure how to implement something like turning the current date and time into a hexadecimal string and using that as a unique field I can use as a primary key. Am I just being too paranoid about running out of space?

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  • Is possible to generate constant value during compilation?

    - by AOI Karasu
    I would like my classes to be identified each type by an unique hash code. But I don't want these hashed to be generated every time a method, eg. int GetHashCode(), is invoked during runtime. I'd like to use already generated constants and I was hoping there is a way to make the compiler do some come computing and set these constants. Can it be done using templates? Could you give me some example, if it is possible.

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  • How should a Gnome applet store its configuration data?

    - by George Edison
    I have a Gnome applet written in Python. In order to save configuration data/settings, it creates a file ~/.appname. However, this prevents multiple instances of the applet from being added to the panel because each cannot have its own settings. How can I store the settings in a way that allows each instance to have its own unique settings? Update: I specifically want to know how to store settings per instance.

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  • How to get the trending tags using php and mysql?

    - by Tom
    Hello I have a table : tags(tagname,entryid,stamp) and i want to make a section for the most trending tags today, the tagname column has no unique value, because many entries has the same tag, so the php code that i want should display the most attached tags today. Note: the "stamp" column is the date of adding the tag in UNIX time stamp format. Thanks

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  • Why One-to-one relationship dosen't work?

    - by eugenn
    I'm trying to create a very simple relationship between two objects. Can anybody explain me why I can't find the Company object via findBy method? class Company { String name String desc City city static constraints = { city(unique: true) } } class City { String name static constraints = { } } class BootStrap { def init = { servletContext -> new City(name: 'Tokyo').save() new City(name: 'New York').save() new Company(name: 'company', city: City.findByName('New York')).save() def c = Company.findByName('company') // Why c=null????! } def destroy = { } }

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  • Grails' GORM constraint question

    - by xain
    Hi, I have the following Domain Class: class Metric { String name float value static belongsTo = [Person,Corporation] static indexes = { name() } } How can I add a constraint so Person,Corporation and name are unique ? Thanks.

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  • sqlite, UPDATE OR REPLACE

    - by acidzombie24
    I do something like UPDATE OR REPLACE someTable SET a=1, b=2 WHERE c=3 I expect if it doesnt exist it will be inserted into the DBs. But nothing happens and i get no errors. How can i insert data, replace it if it already exist and use a where for the condition (instead of replacing BC of a unique ID)

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  • jpa-Google app engine

    - by megala
    I had created entity in google app engie datastore using JPA.I set the id as follows @Id @GeneratedValue(strategy=GenerationType.SEQUENCE) private Long s; After i deployed my applicaiton it give identity (i.e) unique value.but igive 1001,1002,1003 ....as id.But i wnat 1,2,3,4,5 like that.how to achive this? Thanks in advance

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  • C#:checking existing record in database Mysql

    - by Meko
    HI.I searched this question inform and I found solution to change column property Unique Index.Now If I try to insert same record cmd.ExecuteNonQuery() gives error that record exist ,but how can use this exception to give user a message that record exist and must enter new one ? I am trying to make some thing like if(cmd.ExecuteNonQuery() !=true ) { MessageBox.Show("User Exists"); } But I dont know what returns cmd.ExecuteNonQuery() ? Or I must get records using reader in table and compare them with text in Textfiel?

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  • Adding a clustered index to a SQL table: what dangers exist for a live production system?

    - by MoSlo
    Right, keep in mind i need to describe this by abstracting all possible confidential info: I've been put in charge of a 10-year old transactional system of which the majority business logic is implemented at database level (triggers, stored procedures etc). Win2000 server, MSSQL 2000 Enterprise. No immediate plans for replacing/updating the system are being considered :( The core process is a program that executes transactions - specifically, it executes a stored procedure with various parameters, lets call it sp_ProcessTrans. The program executes the stored procedure at asynchronous intervals. By itself, things work fine. But there are 30 instances of this program on remotely located workstations, all of them asynchronously executing sp_ProcessTrans and then retrieving data from the SQL server (execution is pretty regular - ranging 0 to 60 times a minute, depending on what items the program instance is responsible for) . Performance of the system has dropped considerably with 10 yrs of data growth: the reason is the deadlocks and specifically deadlock wait times. The deadlock is on the Employee table. I have discovered: In sp_ProcessTrans' execution, it selects from an Employee table 7 times (dont ask) The select is done on a field that is NOT the primary key No index exists on this field. Thus a table scan is performed. 7 times. per transaction So the reason for deadlocks is clear. I created a non-unique ordered clustered index on the field (field looks good, almost unique, NUM(7), very rarely changes). Immediate improvement in the test environment. The problem is that i cannot simulate the deadlocks in a test environment (I'd need 30 workstations; i'd need to simulate 'realistic' activity on those stations, so visualization is out). I need to know if i must schedule downtime. Creating an index shouldn't be a risky operation for MSSQL, but is there any danger (data corruption in transactions/select statements/extra wait time etc) to create this field index on the production database while the transactions are still taking place? (although i can select a time when transactions are fairly quiet through the 30 stations) Are there any hidden dangers i'm not seeing (not looking forward to needing to restore the DB if something goes wrong, restoring would take a lot of time with 10yrs of data).

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