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  • Common one-to-many table for multiple entities

    - by Ben V
    Suppose I have two tables, Customer and Vendor. I want to have a common address table for customer and vendor addresses. Customers and Vendors can both have one to many addresses. Option 1 Add columns for the AddressID to the Customer and Vendor tables. This just doesn't seem like a clean solution to me. Customer Vendor Address -------- --------- --------- CustomerID VendorID AddressID AddressID1 AddressID1 Street AddressID2 AddressID2 City... Option 2 Move the foreign key to the Address table. For a Customer, Address.CustomerID will be populated. For a Vendor, Address.VendorID will be populated. I don't like this either - I shouldn't need to modify the address table every time I want to use it for another entity. Customer Vendor Address -------- --------- --------- CustomerID VendorID AddressID CustomerID VendorID Option 3 I've also seen this - only 1 foreign key column on the Address table with another column to identify which foreign key table the address belongs to. I don't like this one because it requires all the foreign key tables to have the same type of ID. It also seems messy once you start coding against it. Customer Vendor Address -------- --------- --------- CustomerID VendorID AddressID FKTable FKID So, am I just too picky, or is there something I haven't thought of?

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  • Many to many table design question

    - by user169867
    Originally I had 2 tables in my DB, [Property] and [Employee]. Each employee can have 1 "Home Property" so the employee table has a HomePropertyID FK field to Property. Later I needed to model the situation where despite having only 1 "Home Property" the employee did work at or cover for multiple properties. So I created an [Employee2Property] table that has EmployeeID and PropertyID FK fields to model this many 2 many relationship. Now I find that I need to create other many-to-many relationships between employees and properties. For example if there are multiple employees that are managers for a property or multiple employees that perform maintenance work at a property, etc. My questions are: 1) Should I create seperate many-to-many tables for each of these situations or should I just create 1 more table like [PropertyAssociatonType] that lists the types of associations an emploee can have with a property and just add a FK field to [Employee2Property] such a PropertyAssociationTypeID that explains what the association is? I'm curious about the pros/cons or if there's another better way. 2) Am I stupid and going about this all worng? Thanks for any suggestions :)

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  • Installing CentOS on remote machine.

    - by vijay.shad
    Hi, Can I do a fresh install of centos linux distribution on a remote machine? I have got a machine with windows NT system in a remote location. Now i want to use that system as my deployment machine. To proceed on my plan i need to install a linux os(have chosen CentOS). The guy with machine there is not very much aware of the installation process of any OS. So i thought of the remotely install. Please give me some insight how can i achieve this?

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  • Oracle - Is there any effects of not having a primary key on a table ?

    - by Sathya
    We use sequence numbers for primary keys on the tables. There are some tables where we dont really use the primary key for any querying purpose. But, we have Indexes on other columns. These are non-unique indexes. The queries use these non-primary key columns in the WHERE conditions. So, I dont really see any benefit of having a primary key on such tables. My experience with SQL 2000 was that, it used to replicate tables which had some primary key. Otherwise it would not. I am using Oracle 10gR2. I would like to know if there are any such side-effects of having tables that dont have primary key.

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  • Speeding up inner-joins and subqueries while restricting row size and table membership

    - by hiffy
    I'm developing an rss feed reader that uses a bayesian filter to filter out boring blog posts. The Stream table is meant to act as a FIFO buffer from which the webapp will consume 'entries'. I use it to store the temporary relationship between entries, users and bayesian filter classifications. After a user marks an entry as read, it will be added to the metadata table (so that a user isn't presented with material they have already read), and deleted from the stream table. Every three minutes, a background process will repopulate the Stream table with new entries (i.e. whenever the daemon adds new entries after the checks the rss feeds for updates). Problem: The query I came up with is hella slow. More importantly, the Stream table only needs to hold one hundred unread entries at a time; it'll reduce duplication, make processing faster and give me some flexibility with how I display the entries. The query (takes about 9 seconds on 3600 items with no indexes): insert into stream(entry_id, user_id) select entries.id, subscriptions_users.user_id from entries inner join subscriptions_users on subscriptions_users.subscription_id = entries.subscription_id where subscriptions_users.user_id = 1 and entries.id not in (select entry_id from metadata where metadata.user_id = 1) and entries.id not in (select entry_id from stream where user_id = 1); The query explained: insert into stream all of the entries from a user's subscription list (subscriptions_users) that the user has not read (i.e. do not exist in metadata) and which do not already exist in the stream. Attempted solution: adding limit 100 to the end speeds up the query considerably, but upon repeated executions will keep on adding a different set of 100 entries that do not already exist in the table (with each successful query taking longer and longer). This is close but not quite what I wanted to do. Does anyone have any advice (nosql?) or know a more efficient way of composing the query?

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  • Hibernate design to speed up querying of large dataset

    - by paddydub
    I currently have the below tables representing a bus network mapped in hibernate, accessed from a Spring MVC based bus route planner I'm trying to make my route planner application perform faster, I load all the above tables into Lists to perform the route planner logic. I would appreciate if anyone has any ideas of how to speed my performace Or any suggestions of another method to approach this problem of handling a large set of data Coordinate Connections Table (INT,INT,INT, DOUBLE)( Containing 50,000 Coordinate Connections) ID, FROMCOORDID, TOCOORDID, DISTANCE 1 1 2 0.383657 2 1 17 0.173201 3 1 63 0.258781 4 1 64 0.013726 5 1 65 0.459829 6 1 95 0.458769 Coordinate Table (INT,DECIMAL, DECIMAL) (Containing 4700 Coordinates) ID , LAT, LNG 0 59.352669 -7.264341 1 59.352669 -7.264341 2 59.350012 -7.260653 3 59.337585 -7.189798 4 59.339221 -7.193582 5 59.341408 -7.205888 Bus Stop Table (INT, INT, INT)(Containing 15000 Stops) StopID RouteID COORDINATEID 1000100001 100 17 1000100002 100 18 1000100003 100 19 1000100004 100 20 1000100005 100 21 1000100006 100 22 1000100007 100 23 This is how long it takes to load all the data from each table: stop.findAll = 148ms, stops.size: 15670 Hibernate: select coordinate0_.COORDINATEID as COORDINA1_2_, coordinate0_.LAT as LAT2_, coordinate0_.LNG as LNG2_ from COORDINATES coordinate0_ coord.findAll = 51ms , coordinates.size: 4704 Hibernate: select coordconne0_.COORDCONNECTIONID as COORDCON1_3_, coordconne0_.DISTANCE as DISTANCE3_, coordconne0_.FROMCOORDID as FROMCOOR3_3_, coordconne0_.TOCOORDID as TOCOORDID3_ from COORDCONNECTIONS coordconne0_ coordinateConnectionDao.findAll = 238ms ; coordConnectioninates.size:48132 Hibernate Annotations @Entity @Table(name = "STOPS") public class Stop implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "STOPID") private int stopID; @Column(name = "ROUTEID", nullable = false) private int routeID; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "COORDINATEID", nullable = false) private Coordinate coordinate; } @Table(name = "COORDINATES") public class Coordinate { @Id @GeneratedValue @Column(name = "COORDINATEID") private int CoordinateID; @Column(name = "LAT") private double latitude; @Column(name = "LNG") private double longitude; } @Entity @Table(name = "COORDCONNECTIONS") public class CoordConnection { @Id @GeneratedValue @Column(name = "COORDCONNECTIONID") private int CoordinateID; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "FROMCOORDID", nullable = false) private Coordinate fromCoordID; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "TOCOORDID", nullable = false) private Coordinate toCoordID; @Column(name = "DISTANCE", nullable = false) private double distance; }

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  • Replication - User defined table type not propogating to subscriber

    - by Aamod Thakur
    I created a User defined table type named tvp_Shipment with two columns (id and name) . generated a snapshot and the User defined table type was properly propogated to all the subscribers. I was using this tvp in a stored procedure and everything worked fine. Then I wanted to add one more column created_date to this table valued parameter.I dropped the stored procedure (from replication too) and also i dropped and recreated the User defined table type with 3 columns and then recreated the stored procedure and enabled it for publication When i generate a new snapshot, the changes in user defined table type are not propogated to the subscriber. The newly added column was not added to the subscription. the Error messages: The schema script 'usp_InsertAirSa95c0e23_218.sch' could not be propagated to the subscriber. (Source: MSSQL_REPL, Error number: MSSQL_REPL-2147201001) Get help: http://help/MSSQL_REPL-2147201001 Invalid column name 'created_date'. (Source: MSSQLServer, Error number: 207) Get help: http://help/207

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  • postgresql syntax while exists loop

    - by veilig
    I'm working at function from Joe Celkos book - Trees and Hierarchies in SQL for Smarties I'm trying to delete a subtree from an adjacency list but part my function is not working yet. WHILE EXISTS –– mark leaf nodes (SELECT * FROM OrgChart WHERE boss_emp_nbr = -99999 AND emp_nbr > -99999) LOOP –– get list of next level subordinates DELETE FROM WorkingTable; INSERT INTO WorkingTable SELECT emp_nbr FROM OrgChart WHERE boss_emp_nbr = -99999; –– mark next level of subordinates UPDATE OrgChart SET emp_nbr = -99999 WHERE boss_emp_nbr IN (SELECT emp_nbr FROM WorkingTable); END LOOP; my question: is the WHILE EXISTS correct for use w/ postgresql? I appear to be stumbling and getting caught in an infinite loop in this part. Perhaps there is a more correct syntax I am unaware of.

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  • Data Modeling Help - Do I add another table, change existing table's usage, or something else?

    - by StackOverflowNewbie
    Assume I have the following tables and relationships: Person - Id (PK) - Name A Person can have 0 or more pets: Pet - Id (PK) - PersonId (FK) - Name A person can have 0 or more attributes (e.g. age, height, weight): PersonAttribute _ Id (PK) - PersonId (FK) - Name - Value PROBLEM: I need to represent pet attributes, too. As it turns out, these pet attributes are, in most cases, identical to the attributes of a person (e.g. a pet can have an age, height, and weight too). How do I represent pet attributes? Do I create a PetAttribute table? PetAttribute Id (PK) PetId (FK) Name Value Do I change PersonAttribute to GenericAttribute and have 2 foreign keys in it - one connecting to Person, the other connecting to Pet? GenericAttribute Id (PK) PersonId (FK) PetId (FK) Name Value NOTE: if PersonId is set, then PetId is not set. If PetId is set, PersonId is not set. Do something else?

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  • How to connect to memcached from another machine

    - by Oscar Del Ben
    I'm trying to use memcached from a different machine (which has access to my server), but I can't figure out how. on the memcached machine I can test the connection by running telnet 127.0.0.1 port And it works, but on the other machine it just keeps trying to connect telnet machine_address port Trying machine_address... I'm not sure if I should set up something else to get it working. I know the port is working and accessible because if I try to run other services on it, they works. Os is ubuntu

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  • Is the set of data always normalized in one form or the other in Databases

    - by manugupt1
    Suppose I have a set of data, given the data and the relation schemas can I assume that the set of data is normalized in one form or the other. In my opinion raw data given, has to be normalized into some form. However a discussion with a friend has led to ask me this question here. To expound more on the question, I would say given a set of functional dependencies for a relation or table, is it guaranteed that the table would atleast be in 1NF if not others

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  • What does ER_WARN_FIELD_RESOLVED mean?

    - by VolkerK
    When SHOW WARNINGS after a EXPLAIN EXTENDED shows a Note 1276 Field or reference 'test.foo.bar' of SELECT #2 was resolved in SELECT #1 what exactly does that mean and what impact does it have? In my case it prevents mysql from using what seems to be a perfectly good index. But it's not about fixing that specific query (as it is an irrelevant test). I found http://dev.mysql.com/doc/refman/5.0/en/error-messages-server.html butError: 1276 SQLSTATE: HY000 (ER_WARN_FIELD_RESOLVED) Message: Field or reference '%s%s%s%s%s' of SELECT #%d was resolved in SELECT #%d isn't much of an explaination.

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  • Severe latency only on one machine and only when accessing intranet site

    - by Joe M.
    I have one desktop machine that is having consistently high latency only when trying to load a page from an intranet site. Using the Chrome Developer Tools, the site shows a "Waiting" time of 4-5 seconds each page load. Other machines have <50ms, and the problem machine loads regular internet sites with <1s latency, so the problem is only on one machine and only when accessing the intranet site. This is a small business and all the hosts are on 192.168.0.1/24 I would have suspected a connection issue with the problem machine but normal internet sites are not having latency. Then I would have looked at connection issues with the intranet web server but other machines are not having latency to it. What else can I look at to troubleshoot this?

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  • I want define tables from a part of my ER Diagram.

    - by M R Jafari
    I have a ER-Diagram (Show in http://www.4freeimagehost.com/show.php?i=f82997ca4d5d.png). In the diagram you see 2 entities and a 1:N relataion together. Project has 2 columns as ProjectID, ProjectName. Employee has 3 colums as EmployeeID, EmployeeName and ProjectID. A project has ONLY 1 project-manager and project-manager is a employee. What columns add them?

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  • Define tables from a part of my ER Diagram.

    - by M R Jafari
    I have a ER-Diagram (Show in http://www.4freeimagehost.com/show.php?i=f82997ca4d5d.png). In the diagram you see 2 entities and a 1:N relataion together. Project has 2 columns as ProjectID, ProjectName. Employee has 3 colums as EmployeeID, EmployeeName and ProjectID. A project has ONLY 1 project-manager and project-manager is a employee. What columns add them?

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  • Low cost way to host a large table yet keep the performance scalable?

    - by Leo Liang
    I have a growing table storing time series data, 500M entries now, and 200K new records every day. The total size is around 15GB for now. My clients are querying the table via a PHP script mostly, and the size of the result set is around 10K records (not very large). select * from T where timestamp > X and timestamp < Y and additionFilters And I want this operation cheap. Currently my table is hosting in Postgres 7, on a single 16G memory Box, and I would love to see some good suggestion for me to host this in low cost and also allow me to scale up for performance if needed. The table serves: 1. Query: 90% 2. Insert: 9.9% 2. Update: 0.1% <-- very rare.

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  • MySQL triggers cannot update rows in same table the trigger is assigned to. Suggested workaround?

    - by Cory House
    MySQL doesn't currently support updating rows in the same table the trigger is assigned to since the call could become recursive. Does anyone have suggestions on a good workaround/alternative? Right now my plan is to call a stored procedure that performs the logic I really wanted in a trigger, but I'd love to hear how others have gotten around this limitation. Edit: A little more background as requested. I have a table that stores product attribute assignments. When a new parent product record is inserted, I'd like the trigger to perform a corresponding insert in the same table for each child record. This denormalization is necessary for performance. MySQL doesn't support this and throws: Can't update table 'mytable' in stored function/trigger because it is already used by statement which invoked this stored function/trigger. A long discussion on the issue on the MySQL forums basically lead to: Use a stored proc, which is what I went with for now. Thanks in advance!

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  • how to design a schema where the columns of a table are not fixed

    - by hIpPy
    I am trying to design a schema where the columns of a table are not fixed. Ex: I have an Employee table where the columns of the table are not fixed and vary (attributes of Employee are not fixed and vary). Nullable columns in the Employee table itself i.e. no normalization Instead of adding nullable columns, separate those columns out in their individual tables ex: if Address is a column to be added then create table Address[EmployeeId, AddressValue]. Create tables ExtensionColumnName [EmployeeId, ColumnName] and ExtensionColumnValue [EmployeeId, ColumnValue]. ExtensionColumnName would have ColumnName as "Address" and ExtensionColumnValue would have ColumnValue as address value. Employee table EmployeeId Name ExtensionColumnName table ColumnNameId EmployeeId ColumnName ExtensionColumnValue table EmployeeId ColumnNameId ColumnValue There is a drawback is the first two ways as the schema changes with every new attribute. Note that adding a new attribute is frequent. I am not sure if this is the good or bad design. If someone had a similar decision to make, please give an insight on things like foreign keys / data integrity, indexing, performance, reporting etc.

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  • How to store data in mysql, to get the fastest performance?

    - by Oden
    Hey, I'm thinking about it, witch of the following two query types would give me the fastest performance for a user messaging module inside my site: The first one i thought about is a multi table setup, witch has a connection table, and a main table. The connection table holds the connection between accounts, and the messaging table. In this case a query would look like following, to get some data of the author, and the messages he has sent: SELECT m.*, a.username FROM messages AS m LEFT JOIN connection_table ON (message_id = m.id) LEFT JOIN accounts AS a ON (account_id = a.id) WHERE m.id = '32341' Inserting into it is a little bit more "complicated". My other idea, and in my thought the better solution of this problem is that i store the data i would use in a connection table in the same table where is store the data of the mail. Sounds like i would get lots of duplicated entries, but no, because i have a field witch has text type and holds user ids like this: *24*32*249* If I want to query them, i use the mysql LIKE method. Deleting is an other problem, but for this i have one more field where i store who has deleted the post. Sad about that i don't know how to join this. So what would you recommend? Are there other ways?

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  • run browser from remote machine

    - by cathy02
    Hello, I can connect to a remote machine using ssh, I would like to open a URL from the remote machine. Well, I can do this using lynx (a command line browser), but then, javascript etc... gets messed up. Is there a way I can open the URL and see it in my local machine firefox browser for example ?? Thanks

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  • What is the best schema design for child collection with a "primary" entity

    - by erg39
    Here is the scenario: You have a Persons table with a one-to-many relationship with an Addresses table, where one of the Address rows is the "primary" Address. Is it better in a normalized schema to Use a Persons.PrimaryAddressID to access the "primary" Address for a Person or Use an Addresses.IsPrimary bit column to reference the "primary" Address for a Person via Addresses.PersonID or Other and why?

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  • How to maintain an ordered table with Core Data (or SQL) with insertions/deletions?

    - by Jean-Denis Muys
    This question is in the context of Core Data, but if I am not mistaken, it applies equally well to a more general SQL case. I want to maintain an ordered table using Core Data, with the possibility for the user to: reorder rows insert new lines anywhere delete any existing line What's the best data model to do that? I can see two ways: 1) Model it as an array: I add an int position property to my entity 2) Model it as a linked list: I add two one-to-one relations, next and previous from my entity to itself 1) makes it easy to sort, but painful to insert or delete as you then have to update the position of all objects that come after 2) makes it easy to insert or delete, but very difficult to sort. In fact, I don't think I know how to express a Sort Descriptor (SQL ORDER BY clause) for that case. Now I can imagine a variation on 1): 3) add an int ordering property to the entity, but instead of having it count one-by-one, have it count 100 by 100 (for example). Then inserting is as simple as finding any number between the ordering of the previous and next existing objects. The expensive renumbering only has to occur when the 100 holes have been filled. Making that property a float rather than an int makes it even better: it's almost always possible to find a new float midway between two floats. Am I on the right track with solution 3), or is there something smarter?

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