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  • Database abstraction/adapters for ruby

    - by Stiivi
    What are the database abstractions/adapters you are using in Ruby? I am mainly interested in data oriented features, not in those with object mapping (like active record or data mapper). I am currently using Sequel. Are there any other options? I am mostly interested in: simple, clean and non-ambiguous API data selection (obviously), filtering and aggregation raw value selection without field mapping: SELECT col1, col2, col3 = [val1, val2, val3] not hash of { :col1 = val1 ...} API takes into account table schemas 'some_schema.some_table' in a consistent (and working) way; also reflection for this (get schema from table) database reflection: get list of table columns, their database storage types and perhaps adaptor's abstracted types table creation, deletion be able to work with other tables (insert, update) in a loop enumerating selection from another table without requiring to fetch all records from table being enumerated Purpose is to manipulate data with unknown structure at the time of writing code, which is the opposite to object mapping where structure or most of the structure is usually well known. I do not need the object mapping overhead. What are the options, including back-ends for object-mapping libraries?

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  • select for update with ruby oci8

    - by ash34
    how do I do a 'select for update' and then 'update' the row using ruby oci8. I have two fields counter1 and counter2 in a table which has only 1 record. I want to select the values from this table and then increment them by locking the row using select for update. thanks.

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  • Search sort by parameter match count in the query? PostgreSQL

    - by Ben Dauphinee
    I am working on a search query in PostgreSQL, and one of the things I do is sort my query results by the number of parameters matched. I have no clue how this can be done. Does anyone have a suggestion or solution? Table brand color type engine Ford Blue 4-door V8 Maserati Blue 2-door V12 Saturn Green 4-door V8 GM Yellow 1-door V4 Current Query SELECT brand FROM table WHERE color = 'Blue' or type = '4-door' or engine = 'V8' Result Should Be Ford (3 match) Saturn (2 match) Maserati (1 match)

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  • C# - Rollback SqlTransaction in catch block - Problem with object accessability

    - by Marks
    Hi there. I've got a problem, and all articles or examples i found seem to not care about it. I want to do some database actions in a transaction. What i want to do is very similar to most examples: using (SqlConnection Conn = new SqlConnection(_ConnectionString)) { try { Conn.Open(); SqlTransaction Trans = Conn.BeginTransaction(); using (SqlCommand Com = new SqlCommand(ComText, Conn)) { /* DB work */ } } catch (Exception Ex) { Trans.Rollback(); return -1; } } But the problem is, that the SqlTransaction Trans is declared inside the try block. So it is not accessable in the catch() block. Most examples just do Conn.Open() and Conn.BeginTransaction() before the try block. But i think thats a bit risky, since both can throw multiple exceptions. Am I wrong, or do most people just ignore this risk? Whats the best solution to be able to rollback, if an exception happens. Thanks in advance, Marks

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  • MySQL join problem

    - by David
    Table1 has u_name, Table2 has u_name, u_type and u_admin Table1.u_name is unique. But neither of the 3 fields in Table2 is unique. For any value of Table1.u_name, there are 0 to many entries in Table2 that Table2.u_name equals to that value. For any value of Table1.u_name, there are 0 to 1 entries in Table2 that Table2.u_name equals to that value AND Table2.u_type='S' What I want: Use Table1.u_name to get Table1.*, Table2.u_admin where Table1.u_name=Tabl2.u_name and Table2.u_type='S'. If there is no such entry in Table2 we still need to get Table1.* Please help give me some hints. Thank you so much!

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  • Forum board example schema in YAML format - modify for Nested set?

    - by takeshin
    I have created a forum board app, based on YAML schema found in 'real world examples' of Doctrine Manual, which looks similar to this: --- Forum_Category: columns: root_category_id: integer(10) parent_category_id: integer(10) name: string(50) description: string(99999) relations: Subcategory: class: Forum_Category local: parent_category_id foreign: id Rootcategory: class: Forum_Category local: root_category_id foreign: id Forum_Board: columns: category_id: integer(10) name: string(100) description: string(5000) relations: Category: class: Forum_Category local: category_id foreign: id Threads: class: Forum_Thread local: id foreign: board_id Forum_Entry: columns: author: string(50) topic: string(100) message: string(99999) parent_entry_id: integer(10) thread_id: integer(10) date: integer(10) relations: Parent: class: Forum_Entry local: parent_entry_id foreign: id Thread: class: Forum_Thread local: thread_id foreign: id Forum_Thread: columns: board_id: integer(10) updated: integer(10) closed: integer(1) relations: Board: class: Forum_Board local: board_id foreign: id Entries: class: Forum_Entry local: id foreign: thread_id How to modify this schema, to use NestedSet (Tree structure of threads and entries)?

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  • Writing a query to find MAX number in PL/SQL

    - by user2461116
    I am suppose to Write a query that will display the largest number of movies rented by one member and that member's name. Give the output column a meaningful name such as MAXIMUM NUMBER. This is what I have. select max(maximum_movies) from (select count(*)maximum_movies from mm_member join mm_rental on mm_rental.member_id = mm_member.member_id group by first, last); I got the maximum number but the output should be like this. First Last Maximum_movies John Doe 4 But the output is Maximum_movies 4 Any suggestions?

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  • Where to store site settings: DB? XML? CONFIG? CLASS FILES?

    - by Emin
    I am re-building a news portal of which already have a large number of visits every day. One of the major concerns when re-building this site was to maximize performance and speed. Having said this, we have done many things from caching, to all sort of other measures to ensure speed. Now towards the end of the project, I am having a dilemma of where to store my site settings that would least affect performance. The site settings will include things such as: Domain, DefaultImgPath, Google Analytics code, default emails of editors as well as more dynamic design/display feature settings such as the background color of specific DIVs and default color for links etc.. As far as I know, I have 4 choices in storing all these info. Database: Storing general settings in the DB and caching them may be a solution however, I want to limit the access to the database for only necessary and essential functions of the project which generally are insert/update/delete news items, author articles etc.. XML: I can store these settings in an XML file but I have not done this sort of thing before so I don't know what kind of problems -if any- I might face in the future. CONFIG: I can also store these settings in web.config CLASS FILE: I can hard code all these settings in a SiteSettings class, but since the site admin himself will be able to edit these settings, It may not be the best solution. Currently, I am more close to choosing web.config but letting people fiddle with it too often is something I do not want. E.g. if somehow, I miss out a validation for something and it breaks the web.config, the whole site will go down. My concern basically is that, I cannot forsee any possible consequences of using any of the methods above (or is there any other?), I was hoping to get this question over to more experienced people out here who hopefully help make my decision.

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  • Database indexes and their Big-O notation

    - by miket2e
    I'm trying to understand the performance of database indexes in terms of Big-O notation. Without knowing much about it, I would guess that: Querying on a primary key or unique index will give you a O(1) lookup time. Querying on a non-unique index will also give a O(1) time, albeit maybe the '1' is slower than for the unique index (?) Querying on a column without an index will give a O(N) lookup time (full table scan). Is this generally correct ? Will querying on a primary key ever give worse performance than O(1) ? My specific concern is for SQLite, but I'd be interested in knowing to what extent this varies between different databases too.

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  • Getting a ReturnValue from cmd.Parameters in c#?

    - by mark smith
    Hi, I have just finished converted a vb.net app to c# and one of the lines is to get @ReturnValue from the parameter. I ended up having to CAST a lot of things.. Is there not a easier way here is what i have int rc = ((System.Data.SqlTypes.SqlInt32)(((System.Data.SqlClient.SqlParameter)(cmd.Parameters["@ReturnValue"])).SqlValue)).Value; In vb.net it was as simple as doing this Dim rc As Integer = Convert.ToInt32(cmd.Parameters("@ReturnValue").Value) Alot easier :-) But the problem with C# is the property Value isn't available unless I Cast to SqlParameter and i also need to cast to Sqltypes.SqlInt32 - i can't just do a standard Convert.ToInt32

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  • How to join nearly identical several queries into one?

    - by Devyn
    Hi, Assume I have an order_dummy table where order_dummy_id, order_id, user_id, book_id, author_id are stored. You may complain the logic of my table but I somehow need to do it that way. I want to execute following queries. SELECT * FROM order_dummy WHERE order_id = 1 AND user_id = 1 AND book_id = 1 ORDER BY `order_dummy_id` DESC LIMIT 1 SELECT * FROM order_dummy WHERE order_id = 1 AND user_id = 1 AND book_id = 2 ORDER BY `order_dummy_id` DESC LIMIT 1 SELECT * FROM order_dummy WHERE order_id = 1 AND user_id = 1 AND book_id = 3 ORDER BY `order_dummy_id` DESC LIMIT 1 Please keep in mind that several numbers of same book is included in one order. Therefore, I list order_dummy_id by descending and limit 1 so only LATEST ORDER of A BOOK is shown. But my goal is to show other books in that way in one table. I used group by like this ... SELECT * FROM order_dummy WHERE order_id = 1 AND user_id = 1 GROUP BY book_id but it only shows order_dummy_id with ascending result. I have no idea anymore. Looking forward your kindness help!

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  • Can't use where clause on correlated columns.

    - by Keyo
    I want to add a where clause to make sure video_count is greater than zero. Only categories which are referenced once or more in video_category.video_id should be returned. Because video_count is not a field in any table I cannot do this. Here is the query. SELECT category . * , ( SELECT COUNT( * ) FROM video_category WHERE video_category.category_id = category.category_id ) AS 'video_count' FROM category WHERE category.status = 1 AND video_count > '0' AND publish_date < NOW() ORDER BY updated DESC; Thanks for the help.

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  • PHP tag cloud ( and finding similar ones )

    - by mfolnovich
    Hello! I have articles on my site, and I would like to add tags which would describe each article, but I'm having problems with design mysql table for tags. I have two ideas: 1) each article would have field "tags", and tags would be in format: "tag1,tag2,tag3" 2) create other table called tags with fields: tag_name, article_id, so when I want tags for article with ID 1, I would run SELECT ... FROM tags WHERE news_id=1; But, I would also like to know 3 similar articles by comparing tags, so if I have article which has tags "php,mysql,erlang", and 5 articles with tags: "php,mysql", "erlang,ruby", "php erlang", "mysql,erlang,javascript", I would choose 1., 3. and 4., since those 3 have most same tags with main article. Thanks!

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  • How do I properly use LINQ with MySQL?

    - by Arda Xi
    I've been looking this up on Google for hours, but I haven't found anything conclusive. So far, I've seen a few paid options, an option with NHibernate, but most are marked as unstable or in production. Is there a stable implementation of LINQ for MySQL?

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  • Linq2SQL InfoMessage

    - by Paul Oakham
    Hi, is it possible to access the InfoMessage event handler in a Linq2SQL data context? All of our code uses these messages to display useful information to the end user and since moving to Linq2SQL I cannot figure out how to show these messages. I have checked the connection object of the data context as well as the classes properties with no luck so I'm wondering if it is possible. Thanks in advance.

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  • Insert Stored Procedure does not Create Database Record

    - by SidC
    Hello All, I have the following stored procedure: ALTER PROCEDURE Pro_members_Insert @id int outPut, @LoginName nvarchar(50), @Password nvarchar(15), @FirstName nvarchar(100), @LastName nvarchar(100), @signupDate smalldatetime, @Company nvarchar(100), @Phone nvarchar(50), @Email nvarchar(150), @Address nvarchar(255), @PostalCode nvarchar(10), @State_Province nvarchar(100), @City nvarchar(50), @countryCode nvarchar(4), @active bit, @activationCode nvarchar(50) AS declare @usName as varchar(50) set @usName='' select @usName=isnull(LoginName,'') from members where LoginName=@LoginName if @usName <> '' begin set @ID=-3 RAISERROR('User Already exist.', 16, 1) return end set @usName='' select @usName=isnull(email,'') from members where Email=@Email if @usName <> '' begin set @ID=-4 RAISERROR('Email Already exist.', 16, 1) return end declare @MemID as int select @memID=isnull(max(ID),0)+1 from members INSERT INTO members ( id, LoginName, Password, FirstName, LastName, signupDate, Company, Phone, Email, Address, PostalCode, State_Province, City, countryCode, active,activationCode) VALUES ( @Memid, @LoginName, @Password, @FirstName, @LastName, @signupDate, @Company, @Phone, @Email, @Address, @PostalCode, @State_Province, @City, @countryCode, @active,@activationCode) if @@error <> 0 set @ID=-1 else set @id=@memID Note that I've "inherited" this sproc and the database. I am trying to insert a new record from my signup.aspx page. My SQLDataSource is as follows: <asp:SqlDataSource runat="server" ID="dsAddMember" ConnectionString="rmsdbuser" InsertCommandType="StoredProcedure" InsertCommand="Pro_members_Insert" ProviderName="System.Data.SqlClient"> The click handler for btnSave is as follows: Protected Sub btnSave_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btnSave.Click Try dsAddMember.DataBind() Catch ex As Exception End Try End Sub When I run this page, signup.aspx, provide required fields and click submit, the page simply reloads and the database table does not reflect the newly-inserted record. Questions: 1. How do I catch the error messages that might be returned from the sproc? 2. Please advise how to change signup.aspx so that the insert occurs. Thanks, Sid

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  • Merge computed data from two tables back into one of them

    - by Tyler McHenry
    I have the following situation (as a reduced example). Two tables, Measures1 and Measures2, each of which store an ID, a Weight in grams, and optionally a Volume in fluid onces. (In reality, Measures1 has a good deal of other data that is irrelevant here) Contents of Measures1: +----+----------+--------+ | ID | Weight | Volume | +----+----------+--------+ | 1 | 100.0000 | NULL | | 2 | 200.0000 | NULL | | 3 | 150.0000 | NULL | | 4 | 325.0000 | NULL | +----+----------+--------+ Contents of Measures2: +----+----------+----------+ | ID | Weight | Volume | +----+----------+----------+ | 1 | 75.0000 | 10.0000 | | 2 | 400.0000 | 64.0000 | | 3 | 100.0000 | 22.0000 | | 4 | 500.0000 | 100.0000 | +----+----------+----------+ These tables describe equivalent weights and volumes of a substance. E.g. 10 fluid ounces of substance 1 weighs 75 grams. The IDs are related: ID 1 in Measures1 is the same substance as ID 1 in Measures2. What I want to do is fill in the NULL volumes in Measures1 using the information in Measures2, but keeping the weights from Measures1 (then, ultimately, I can drop the Measures2 table, as it will be redundant). For the sake of simplicity, assume that all volumes in Measures1 are NULL and all volumes in Measures2 are not. I can compute the volumes I want to fill in with the following query: SELECT Measures1.ID, Measures1.Weight, (Measures2.Volume * (Measures1.Weight / Measures2.Weight)) AS DesiredVolume FROM Measures1 JOIN Measures2 ON Measures1.ID = Measures2.ID; Producing: +----+----------+-----------------+ | ID | Weight | DesiredVolume | +----+----------+-----------------+ | 4 | 325.0000 | 65.000000000000 | | 3 | 150.0000 | 33.000000000000 | | 2 | 200.0000 | 32.000000000000 | | 1 | 100.0000 | 13.333333333333 | +----+----------+-----------------+ But I am at a loss for how to actually insert these computed values into the Measures1 table. Preferably, I would like to be able to do it with a single query, rather than writing a script or stored procedure that iterates through every ID in Measures1. But even then I am worried that this might not be possible because the MySQL documentation says that you can't use a table in an UPDATE query and a SELECT subquery at the same time, and I think any solution would need to do that. I know that one workaround might be to create a new table with the results of the above query (also selecting all of the other non-Volume fields in Measures1) and then drop both tables and replace Measures1 with the newly-created table, but I was wondering if there was any better way to do it that I am missing.

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  • Copying Data between table without identity column

    - by user668479
    I have two table and I need to copy the data across from SRCServiceUsers to Clients Everytime i run it I get the following: Violation of PRIMARY KEY constraint 'PK_Clients'. Cannot insert duplicate key in object 'dbo.Clients'. The statement has been terminated. The Primary key ClientId field is not an identity column and therefore requires filling To date I have the following insert into Clients( ClientID, Title, Forenames, FamilyName, [Address], Town, County, PostCode, PhoneNumber, StartDate) SELECT ( Select Max(Clients.ClientID)+ 1, SRCServiceUsers.Title, SRCServiceUsers.[First Names], SRCServiceUsers.Surname, --BUILD UP MUITIPLE COLUMNS SRCServiceUsers.[Property Name] + ', ' + SRCServiceUsers.Street + ', ' + SRCServiceUsers.Suburb as [Address], SRCServiceUsers.Town, SRCServiceUsers.County, SRCServiceUsers.Postcode, SRCServiceUsers.Telephone, SRCServiceUsers.[Start Date] From srcsERVICEuSERS How can i autoincrement the PK field - CLientID when inserting the data? Many thanks Andrew

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  • how can i pass parameter to linq query

    - by girish
    i want to pass parameter to linq query... public IEnumerable GetPhotos() { PhotoDBDataContext db = new PhotoDBDataContext(); var tProduct = db.Photos; var query = from p in db.Photos orderby p.PhotoId descending select new { p.Album, p.AlbumId, p.Description, p.Photographer, p.PhotographerId, p.PhotoId, p.Tags, p.Thumbnail, p.Url }; return query; } in above example "orderby p.PhotoId descending" is used, i want to use parameter in place of p.PhotoId is it possible...

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