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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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  • 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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  • 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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  • 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 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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  • 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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  • 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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  • InnoDB or MyISAM - Why not both?

    - by Skoder
    Hey. I'm new to databases, and I've read various threads about which is better between InnoDB and MyISAM. It seems that the debates are to use or the other. Is it not possible to use both, depending on the table? What would be the disadvantages in doing this? As far as I can tell, the engine can be set during the CREATE TABLE command. Therefore, certain tables which are often read can be set to MyISAM, but tables that need transaction support can use InnoDB. I'm sure there must be a problem, otherwise this would be the ultimate answer :).

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  • How do I create a free server-side database to be accessed via Windows forms and/or browser?

    - by NoCatharsis
    I have no formal education in databasing or programming, but I've learned enough SQL, C++, and C# to at least get started setting up a small database on my company's server. Using MS SQL Server 2008 R2, I have created the database and set up columns with proper data types. However, there seems to be a lot of tweaks and details that are way over my head. Since I would like these data to be accessible to the other 7 or 8 people in my office (preferably via web browser), I'm wondering whether this is the best setup for my situation. The other option I've read about is a LAMPP server, which I assume is the competing free option to Microsoft's Express packages. I know nothing of LAMP servers except from the articles I've read on how to set them up (and I believe I even saw a detailed tutorial somewhere). To summarize, my question is this: Which of these (or any other) server setups would best suit my purposes, keeping in mind that I'm a true novice (but willing to learn), and would like to keep it free until I get more experience?

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  • Reorganizing development environment for single developer/small shop

    - by Matthew
    I have been developing for my company for approximately three years. We serve up a web portal using Microsoft .NET and MS SQL Server on DotNetNuke. I am going to leave my job full time at the end of April. I am leaving on good terms, and I really care about this company and the state of the web project. Because I haven't worked in a team environment in a long time, I have probably lost touch with what 'real' setups look like. When I leave, I predict the company will either find another developer to take over, or at least have developers work on a contractual basis. Because I have not worked with other developers, I am very concerned with leaving the company (and the developer they hire) with a jumbled mess. I'd like to believe I am a good developer and everything makes sense, but I have no way to tell. My question, is how do I set up the development environment, so the company and the next developer will have little trouble getting started? What would you as a developer like in place before working on a project you've never worked on? Here's some relevant information: There is a development server onsite and a production server offsite in a data center . There is a server where backups and source code (Sourcegear Vault) are stored. There is no formal documentation but there are comments in the code. The company budget is tight so free suggestions will help the best. I will be around after the end of April on a consulting basis so I can ask simple questions but I will not be available full time to train someone

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  • Relational MySQL - fetched properties?

    - by Kelso.b
    I'm currently using the following PHP code: // Get all subordinates $subords = array(); $supervisorID = $this->session->userdata('supervisor_id'); $result = $this->db->query(sprintf("SELECT * FROM users WHERE supervisor_id=%d AND id!=%d",$supervisorID, $supervisorID)); $user_list_query = 'user_id='.$supervisorID; foreach($result->result() as $user){ $user_list_query .= ' OR user_id='.$user->id; $subords[$user->id] = $user; } // Get Submissions $submissionsResult = $this->db->query(sprintf("SELECT * FROM submissions WHERE %s", $user_list_query)); $submissions = array(); foreach($submissionsResult->result() as $submission){ $entriesResult = $this->db->query(sprintf("SELECT * FROM submittedentries WHERE timestamp=%d", $submission->timestamp)); $entries = array(); foreach($entriesResult->result() as $entries) $entries[] = $entry; $submissions[] = array( 'user' => $subords[$submission->user_id], 'entries' => $entries ); $entriesResult->free_result(); } Basically I'm getting a list of users that are subordinates of a given supervisor_id (every user entry has a supervisor_id field), then grabbing entries belonging to any of those users. I can't help but think there is a more elegant way of doing this, like SELECT FROM tablename where user->supervisor_id=2222 Is there something like this with PHP/MySQL? Should probably learn relational databases properly sometime. :(

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  • Is it possible to listen to relational database update?

    - by Morgan Cheng
    Is it possible to listen to relation database update? For example, my web app want to send data update to client through Comet technology. I can have the program to poll the database periodically, but that would not be performant and scalable. If app can hood to a "event handler" of database, then app can get notification every time given database table data is updated. This sounds more promising, but I didn't find any concrete example for it. This is listener pattern. Does common relational database support such feature?

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  • Whats the best solution for a database used in conjunction with Maps in Android?

    - by Andrew
    Could someone please point me in the right direction. My project involves a database where users enter their address and other info from my website. This database is then referenced in my android application to show the locations of these addresses in my database. I have yet to start and just came up with this idea. My question is, what would be the best method to create a database easily modified through my website (mySQL, php, etc), and also easily referenced easily through Android and the Google Maps API? I need some ideas on the languages I will need to use to create this database and website so I can go buy the necessary books to start reading up. Thanks so much

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  • How do you store sets in Cassandra?

    - by Ben W
    I'd like to convert this JSON to a data model in Cassandra, where each of the arrays is a set with no duplicates: var data = { "data1": { "100": [1, 2, 3], "200": [3, 4] }, "data2": { "k1", [1], "k2", [4, 5] } } I'd like to query like this: data["data1"]["100"] to retrieve the sets. Anyone know how you might model this in Cassandra? (The only thing I came up with was columns whose name was a set value and the value of the column was an empty string, but that felt wrong.) It's not OK to serialize the sets as JSON or some other string, which would make this much easier. Also, I should note that it's OK to split data1 and data2 into separate ColumnFamilies, it's not necessary that they're keys in the same one.

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  • what concepts every .NET developer should understand?

    - by EquinoX
    Please throw in the core concepts of what every .NET developer should know about? I am asking here about concepts specific to .NET and not web developer in general... Maybe concepts that are most likely to be asked in interview? As a general web developer, javascript and css are definitely a must. Share your ideas here guys

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  • What are some useful SQL statements that should be known by all developers who may touch the Back en

    - by Jian Lin
    What are some useful SQL statements that should be known by all developers who may touch the Back end side of the project? (Update: just like in algorithm, we know there are sorting problems, shuffling problems, and we know some solutions to them. This question is aiming at the same thing). For example, ones I can think of are: Get a list of Employees and their boss. Or one with the employee's salary greater than the boss. (Self-join) Get a list of the most popular Classes registered by students, from the greatest number to the smallest. (Count, group by, order by) Get a list of Classes that are not registered by any students. (Outer join and check whether the match is NULL, or by Get from Classes table, all ClassIDs which are NOT IN (a subquery to get all ClassIDs from the Registrations table)) Are there some SQL statements that should be under the sleeve of all developers that might touch back end data?

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  • Using "CASE" in Where clause to choose various column harm the performance

    - by zivgabo
    I have query which needs to be dynamic on some of the columns, meaning I get a parameter and according its value I decide which column to fetch in my Where clause. I've implemented this request using "CASE" expression: (CASE @isArrivalTime WHEN 1 THEN ArrivalTime ELSE PickedupTime END) >= DATEADD(mi, -@TZOffsetInMins, @sTime) AND (CASE @isArrivalTime WHEN 1 THEN ArrivalTime ELSE PickedupTime END) < DATEADD(mi, -@TZOffsetInMins, @fTime) If @isArrivalTime = 1 then chose ArrivalTime column else chose PickedupTime column. I have a clustered index on ArrivalTime and nonclustered index on PickedupTime. I've noticed that when I'm using this query (with @isArrivalTime = 1), my performance is a lot worse comparing to only using ArrivalTime. Maybe the query optimizer can't use\choose the index properly in this way? I compared the execution plans an noticed that when I'm using the CASE 32% of the time is being wasted on the index scan, but when I didn't use the CASE(just usedArrivalTime`) only 3% were wasted on this index scan. Anyone know the reason for this?

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  • general things developer must know having 2+ years of exp?

    - by Salil
    Hi All, I have 2 years of experience in Ruby on Rails. I have basic knowledge (Very Basic) of mysql such as data insertion, join, select from more than one table. But now i want to know more about it cause my friends are having trouble in interview when ask questions like 1] What is the trigger. 2] which trigger call when 3] what's views in mysql? etc....... are this questions for developers?is it basic database? Also what other things developer should know having experience of 2 years or more. I am in double mind as i have over two years of exp. in ruby and i am learning new thing everyday in ruby only. if someone ask me to rate yourself i can't give more than 5 out of 10 in ROR only. So my question is What are the general things developer must know having 2+ years of exp? Regards, Salil Gaikwad

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  • How to use Unique Composite Key

    - by LifeH2O
    I have a table Item(ItemName*, ItemSize*, Price, Notes) I was making composite key of (ItemName,ItemSize) to uniquely identify item. And now after reading some answers on stackoverflow suggesting the use of UNIQUE i revised it as Item(ItemID*, ItemName, ItemSize, Price, Notes) But How to apply UNIQUE constraint on ItemName and ItemSize please correct if there is something wrong in question

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  • What are some useful SQL statements / usage patterns that should be known by all developers who may

    - by Jian Lin
    What are some useful SQL statements that should be known by all developers who may touch the Back end side of the project? (Update: just like in algorithm, we know there are sorting problems, shuffling problems, and we know some solutions to them. This question is aiming at the same thing). For example, ones I can think of are: Get a list of Employees and their boss. Or one with the employee's salary greater than the boss. (Self-join) Get a list of the most popular Classes registered by students, from the greatest number to the smallest. (Count, group by, order by) Get a list of Classes that are not registered by any students. (Outer join and check whether the match is NULL, or by Get from Classes table, all ClassIDs which are NOT IN (a subquery to get all ClassIDs from the Registrations table)) Are there some SQL statements that should be under the sleeve of all developers that might touch back end data?

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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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