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  • DB Architecture : Linking to intersection or to main tables?

    - by Jean-Nicolas
    Hi, I'm creating fantasy football system on my website but i'm very confuse about how I should link some of my table. Tables The main table is Pool which have all the info about the ruling of the fantasy draft. A standard table User, which contains the usual stuff. Intersection table called pools_users which contains id,pool_id,user_id because a user could be in more than one pool, and a pool contains more than 1 user. The problem Table Selections = that's the table that is causing problem. That's the selection that the user choose for his pool. This is related to the Player table but thats not relevant for this problem. Should I link this table to the table Pools_users or should I link it with both main table Pool and User. This table contains id,pool_id,user_id,player_id,... What is the best way link my tables? When I want to retrieve my data, I normally want the information to be divided BY users. "This user have those selections, this one those selections, etc).

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  • filter duplicates in SQL join

    - by Will
    When using a SQL join, is it possible to keep only rows that have a single row for the left table? For example: select * from A, B where A.id = B.a_id; a1 b1 a2 b1 a2 b2 In this case, I want to remove all except the first row, where a single row from A matched exactly 1 row from B. I'm using MySQL.

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  • Question about OOP and objects.

    - by loddn
    I have a school assignment, a Dog Show. My assignment is to create a website where vistors can display results and Judges and Secretary can admin, crud. I have a small problem one part of the assignment. The result should be based on two protokols from different judges and after that checked by the secretary before the result is displayed for the user. I have to say i'm fairly new to programming and so i need some smart suggestions on how to design and implement this. The assignment should cover both a db and c# (.net mvc). Q1: How do i create a object (result)that depends on two other objects(protocol)? Is that even needed? Q2: How to solve this in a relational db?

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  • sqlite3 date operations when joining two tables in a view?

    - by duncan
    In short, how to add minutes to a datetime from an integer located in another table, in one select statement, by joining them? I have a table P(int id, ..., int minutes) and a table S(int id, int p_id, datetime start) I want to generate a view that gives me PS(S.id, P.id, S.start + P.minutes) by joining S.p_id=P.id The problem is, if I was generating the query from the application, I can do stuff like: select datetime('2010-04-21 14:00', '+20 minutes'); 2010-04-21 14:20:00 By creating the string '+20 minutes' in the application and then passing it to sqlite. However I can't find a way to create this string in the select itself: select p.*,datetime(s.start_at, formatstring('+%s minutes', p.minutes)) from p,s where s.p_id=p.id; Because sqlite as far the documentation tells, does not provide any string format function, nor can I see any alternative way of expressing the date modifiers.

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  • Best way to model Customer <--> Address

    - by Jen
    Every Customer has a physical address and an optional mailing address. What is your preferred way to model this? Option 1. Customer has foreign key to Address Customer (id, phys_address_id, mail_address_id) Address (id, street, city, etc.) Option 2. Customer has one-to-many relationship to Address, which contains a field to describe the address type Customer (id) Address (id, customer_id, address_type, street, city, etc.) Option 3. Address information is de-normalized and stored in Customer Customer (id, phys_street, phys_city, etc. mail_street, mail_city, etc.) One of my overriding goals is to simplify the object-relational mappings, so I'm leaning towards the first approach. What are your thoughts?

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  • Alter multiple tables' columns length

    - by gdoron
    So, we just found out that 254 tables in our Oracle DBMS have one column named "Foo" with the wrong length- Number(10) instead of Number(3). That foo column is a part from the PK of the tables. Those tables have other tables with forigen keys to it. What I did is: backed-up the table with a temp table. Disabled the forigen keys to the table. Disabled the PK with the foo column. Nulled the foo column for all the rows. Restored all the above But now we found out it's not just couple of tables but 254 tables. Is there an easy way, (or at least easier than this) to alter the columns length? P.S. I have DBA permissions.

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  • How can several different datatypes be saved in one table

    - by poseidon
    This is my situation: I am constructing an ad-like application in Django and Mysql. I am using a flexible-ad approach where we have: a table with ad categories (several categories such as home, furniture, cars, etc.) id_category name a table with details for the ad categories (home: area, squared meters. car: seats, color.) id_detail id_category (the categ the detail describes) name type (boolean, char, int, long, etc.) the ad table (i am selling a house. i am selling a car.) id_ad id_category text date a table where i plan to consolidate the details of the ads (home: A-area, 500 sq-meters. car: 5 seats, red.) id_detail_ad id_ad id_detail value Is this possible? Can I have a table of details for all the ads, even if details include numbers, texts, booleans, etc? Or would I have to save them all as text and then interpret them via code accordingly? Please express your opinions. Thank you.

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  • why does cx_oracle execute() not like my string now?

    - by Frank Stallone
    I've downloaded cx_oracle some time ago and wrote a script to convert data to XML. I've had to reisntall my OS and grabbed the latest version of cx_Oracle (5.0.3) and all of the sudden my code is broken. The first thing was that cx_Oracle.connect wanted unicode rather string for the username and password, that was very easy to fix. But now it keeps failing on the cursor.execute and tells me my string is not a string even when type() tells me it is a string. Here is a test script I initally used ages ago and worked fine on my old version but does not work on cx_Oracle now. import cx_Oracle ip = 'url.to.oracle' port = 1521 SID = 'mysid' dsn_tns = cx_Oracle.makedsn(ip, port, SID) connection = cx_Oracle.connect(u'name', u'pass', dsn_tns) cursor = connection.cursor() cursor.arraysize = 50 sql = "select isbn, title_code from core_isbn where rownum<=20" print type(sql) cursor.execute(sql) for isbn, title_code in cursor.fetchall(): print "Values from DB:", isbn, title_code cursor.close() connection.close() When I run that I get: Traceback (most recent call last): File "C:\NetBeansProjects\Python\src\db_temp.py", line 48, in cursor.execute(sql) TypeError: expecting None or a string Does anyone know what I may be doing wrong?

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  • Is foreign key reference from two different primary key from two different tables valid?

    - by arundex
    I have a foreign key that has to refer primary keys of two different tables. Table 1: animal animal_ id (primary key) Table 2: bird bird_ id (primary key) Table 3: Pet_info pet_id, type ENUM ('bird', 'animal') foreign key (pet_ id) references animal(animal_id), bird(bird_id) So, I need to check for pet_id either from animal or bird table depending on the need. Is this valid? Or should I go for some restructuring . . . NOTE: I referred this . . but I'm not sure whether I have to change my existing design

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  • Data Warehouse: Modelling a future schedule

    - by Pat
    I'm creating a DW that will contain data on financial securities such as bonds and loans. These securities are associated with payment schedules. For example, a bond could pay quarterly, while a mortage would usually pay monthly (sometimes biweekly). The payment schedule is created when the security is traded and, in the majority of cases, will remain unchanged. However, the design would need to accomodate those cases where it does change. I'm currently attempting to model this data and I'm having difficulty coming up with a workable design. One of the most commonly queried fields is "next payment date". Users often want to know when a security will pay next. Therefore, I want to make it as easy as possible for them to get the next payment date and amount for each security. Also, users often run historical queries in which case they'd want the next payment date and amount as of a specific point in time. For example, they may want to look back at 1/31/09 and query the next payment dates (which would usually be in February 2009 for mortgages). It's also common that they want to query a security's entire payment schedule, which might consist of 360 records (30 year mortgage x 12 payments/year). Since the next payment date and amount would be changing each month or even biweekly, these fields wouldn't seem to fit into a slow-changing dimension very well. It would probably make more sense to use a fact table, but I'm unsure of how to model it. Any ideas would be greatly appreciated.

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  • Can you modify SQL DB schema in a transaction to know if all changes were applied?

    - by Chris F
    As part of my (new) database version control methodology, I'm writing a "change script" and want the change script to insert a new row into the SchemaChangeLog table if the script is executed successfully, or to reverse changes if any single change in the script fails. Is it possible to do schema changes in a transaction and only if it gets committed to then do the INSERT? For example (psuedo-code, I'm not too good with SQL): SET XACT_ABORT ON BEGIN TRANSACTION PRINT 'Add Col2 to Table1' IF NOT EXIST (SELECT * FROM sys.columns WHERE NAME='Col2' AND object_id=OBJECT_ID('Table1')) BEGIN ALTER TABLE [dbo].[Table1] ADD Col2 int NULL END -- maybe COMMIT here? INSERT INTO SchemaChangeLog VALUES(...) COMMIT TRANSACTION

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  • Multimap Space Issue: Guava

    - by Arpssss
    In my Java code, I am using Guavas Multimap (com.google.common.collect.Multimap) by using this: Multimap< Integer, Integer Index = HashMultimap.create() Here, Multimap key is some portion of URL and value is another portion of URL (converted into integer). Now, I assign my JVM 2560 Mb (2.5 GB) heap space (by using Xmx and Xms). However, it can only store 9 millions of such (key,value) pairs of integers (approx 10 million). But, theoretically (according to memory occupied by int) it should store more. Can anybody help me, 1) Why is this happening (means Multimap is taking lots of space) ? I checked my code with out inserting pairs in Multimap, it takes only 1/2 MB space. 2) Is there any other way or home-baked solution to solve this space issue ? More clearly, how to solve this memory issue ? Thanks in advance and any idea is perfectly OK for me.

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  • MongoDB or CouchDB - fit for production?

    - by Alan
    I was wondering if anyone can tell me if MongoDB or CouchDB are ready for a production environment. I'm now looking at these storage solutions (I'm favouring MongoDB at the moment), however these projects are quite young and so I foresee that I'm going to have to work quite hard to convince my manager that we should adopt this new technology. What I'd like to know is: 1) Who is using MongoDB or CouchDB today in a production environment? 2) How are you using MongoDB/CouchDB? 3) What problems (if any) did you come across when you adopted this new storage mechanism (and how did you overcome them)? 4) How did you deal with any migration issues that you had to deal with? 5) Do you have any good/bad experiences with either of these solutions that you'd like to share? Thanks.

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  • How to store MySQL query results in another Table?

    - by Taz
    How to store results from following query into another table. Considering there is an appropriate table already created. SELECT labels.label,shortabstracts.ShortAbstract,images.LinkToImage,types.Type FROM ner.images,ner.labels,ner.shortabstracts,ner.types WHERE labels.Resource=images.Resource AND labels.Resource=shortabstracts.Resource AND labels.Resource=types.Resource;

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  • sql combine two subqueries

    - by Claudiu
    I have two tables. Table A has an id column. Table B has an Aid column and a type column. Example data: A: id -- 1 2 B: Aid | type ----+----- 1 | 1 1 | 1 1 | 3 1 | 1 1 | 4 1 | 5 1 | 4 2 | 2 2 | 4 2 | 3 I want to get all the IDs from table A where there is a certain amount of type 1 and type 3 actions. My query looks like this: SELECT id FROM A WHERE (SELECT COUNT(type) FROM B WHERE B.Aid = A.id AND B.type = 1) = 3 AND (SELECT COUNT(type) FROM B WHERE B.Aid = A.id AND B.type = 3) = 1 so on the data above, just the id 1 should be returned. Can I combine the 2 subqueries somehow?

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  • How to query range of data in DB2 with highest performance?

    - by Fuangwith S.
    Usually, I need to retrieve data from a table in some range; for example, a separate page for each search result. In MySQL I use LIMIT keyword but in DB2 I don't know. Now I use this query for retrieve range of data. SELECT * FROM( SELECT SMALLINT(RANK() OVER(ORDER BY NAME DESC)) AS RUNNING_NO , DATA_KEY_VALUE , SHOW_PRIORITY FROM EMPLOYEE WHERE NAME LIKE 'DEL%' ORDER BY NAME DESC FETCH FIRST 20 ROWS ONLY ) AS TMP ORDER BY TMP.RUNNING_NO ASC FETCH FIRST 10 ROWS ONLY but I know it's bad style. So, how to query for highest performance?

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  • Better data-structure design

    - by Tempname
    Currently in my application I have a single table that is giving me a bit of trouble. The issue at hand is I have a value object that is mapped to this table. When the data is returned to me as an array of value objects, I have to then loop through this array and begin my recursion by matching the ParentID to parent ObjectID's. The column ParentID is either null (acts a parent) or it holds the value of an ObjectID. I know there has to be a better way to create this data structure so that I do not have to do recursive loops to match ParentID's with their ObjectID's. Any help with this is greatly appreciated. Here is the table in describe form: +----------------+------------------+------+-----+---------------------+-----------------------------+ | Field | Type | Null | Key | Default | Extra | +----------------+------------------+------+-----+---------------------+-----------------------------+ | ObjectID | int(11) unsigned | NO | PRI | NULL | auto_increment | | ObjectHeight | decimal(6,2) | NO | | NULL | | | ObjectWidth | decimal(6,2) | NO | | NULL | | | ObjectX | decimal(6,2) | NO | | NULL | | | ObjectY | decimal(6,2) | NO | | NULL | | | ObjectLabel | varchar(255) | NO | | NULL | | | TemplateID | int(11) unsigned | NO | MUL | NULL | | | ObjectTypeID | int(11) unsigned | NO | MUL | NULL | | | ParentID | int(11) unsigned | YES | MUL | NULL | | | CreationDate | datetime | YES | | 0000-00-00 00:00:00 | | | LastModifyDate | timestamp | YES | | NULL | on update CURRENT_TIMESTAMP | +----------------+------------------+------+-----+---------------------+-----------------------------+e

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