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  • Facebook database design?

    - by Marin
    I have always wondered how Facebook designed the friend <- user relation. I figure the user table is something like this: user_email PK user_id PK password I figure the table with user's data (sex, age etc connected via user email I would assume). How does it connect all the friends to this user? Something like this? user_id friend_id_1 friend_id_2 friend_id_3 friend_id_N Probably not. Because the number of users is unknown and will expand.

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  • What data structures and algorithms are applied within data warehouse cubes?

    - by Jeff Meatball Yang
    I understand that cubes are optimized data structures for aggregating and "slicing" large amounts of data. I just don't know how they are implemented. I can imagine a lot of this technology is proprietary, but are there any resources that I could use to start implementing my own cube technology? Set theory and lots of math are probably involved (and welcome as suggestions!), but I'm primarily interested in implementations: the data structures and query algorithms. Thanks!

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  • Join one row to multiple rows in another table

    - by Ghostrider
    I have a table to entities (lets call them people) and properties (one person can have an arbitrary number of properties). Ex: People Name Age -------- Jane 27 Joe 36 Jim 16 Properties Name Property ----------------- Jane Smart Jane Funny Jane Good-looking Joe Smart Joe Workaholic Jim Funny Jim Young I would like to write an efficient select that would select people based on age and return all or some of their properties. Ex: People older than 26 Name Properties Jane Smart, Funny, Good-looking Joe Smart, Workaholic It's also acceptable to return one of the properties and total property count. The query should be efficient: there are millions of rows in people table, hundreds of thousands of rows in properties table (so most people have no properties). There are hundreds of rows selected at a time. Is there any way to do it?

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  • Query a range of date

    - by juniorSE
    Hello Guys, Im trying to query a sort of from - to date. e.g. 20-01-2010 to 20-02-2010. this should include the mentioned dates. i've tried the following queries but none works. select * from [tableName] where date = '20-01-2010' AND date <= '20-02-2010' the date where date is equal to 20-02-2010 does not show. i don't know why. select * from [tableName] where date between '20-01-2010' AND '20-02-2010' the mentioned dates is not included in the results. i want it to be included in the results. please help. thanks in advance! :)

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  • Aggregate Functions on subsets of data based on current row values with SQL

    - by aasukisuki
    Hopefully that title makes sense... Let's say I have an employee table: ID | Name | Title | Salary ---------------------------- 1 | Bob | Manager | 15285 2 | Joe | Worker | 10250 3 | Al | Worker | 11050 4 | Paul | Manager | 16025 5 | John | Worker | 10450 What I'd like to do is write a query that will give me the above table, along with an averaged salary column, based on the employee title: ID | Name | Title | Salary | Pos Avg -------------------------------------- 1 | Bob | Manager | 15285 | 15655 2 | Joe | Worker | 10250 | 10583 3 | Al | Worker | 11050 | 10583 4 | Paul | Manager | 16025 | 15655 5 | John | Worker | 10450 | 10583 I've tried doing this with a sub-query along the lines of: Select *, (select Avg(e2.salary) from employee e2 where e2.title = e.title) from employee e But I've come to realize that the sub-query is executed first, and has no knowledge of the table alias'd e I'm sure I'm missing something REALLY obvious here, can anyone point me in the right diretion?

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  • C# SqlDataAdapter not populating DataSet

    - by Wesley
    I have searched the net and searched the net only to not quite find the probably I am running into. I am currently having an issue getting a SqlDataAdapter to populate a DataSet. I am running Visual Studio 2008 and the query is being sent to a local instance of SqlServer 2008. If I run the query itself in SqlServer, I do get information. Code is as follows: string theQuery = "select Password from Employees where employee_ID = '@EmplID'"; SqlDataAdapter theDataAdapter = new SqlDataAdapter(); theDataAdapter.SelectCommand = new SqlCommand(theQuery, conn); theDataAdapter.SelectCommand.Parameters.Add("@EmplID", SqlDbType.VarChar).Value = "EmployeeName"; theDataAdapter.Fill(theSet); The code to read the dataset: foreach (DataRow theRow in theSet.Tables[0].Rows) { //process row info } If there is any more info I can supply please let me know.

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  • How to clean sys.conversation_endpoints

    - by Manjoor
    I have a table, a trigger on the table implemented using service broker. More than Half million records are inserted daily into the table. The asynchronous SP is used to check sveral condition by using inserted data and update other tables. It was running fine for last 1 month and the SP was get executed withing 2-3 seconds of insertion of record. But now it take more than 90 minute. At present sys.conversation_endpoints have too much records. (Note that all the table are truncated daily as I do not need those records day after) Other database activities are normal (average 60% CPU Utilization). Now where i need to look?? I can re-create database without any problem but i don't think it is a good way to resolve the problem

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  • Optimize date query for large child tables: GiST or GIN?

    - by Dave Jarvis
    Problem 72 child tables, each having a year index and a station index, are defined as follows: CREATE TABLE climate.measurement_12_013 ( -- Inherited from table climate.measurement_12_013: id bigint NOT NULL DEFAULT nextval('climate.measurement_id_seq'::regclass), -- Inherited from table climate.measurement_12_013: station_id integer NOT NULL, -- Inherited from table climate.measurement_12_013: taken date NOT NULL, -- Inherited from table climate.measurement_12_013: amount numeric(8,2) NOT NULL, -- Inherited from table climate.measurement_12_013: category_id smallint NOT NULL, -- Inherited from table climate.measurement_12_013: flag character varying(1) NOT NULL DEFAULT ' '::character varying, CONSTRAINT measurement_12_013_category_id_check CHECK (category_id = 7), CONSTRAINT measurement_12_013_taken_check CHECK (date_part('month'::text, taken)::integer = 12) ) INHERITS (climate.measurement) CREATE INDEX measurement_12_013_s_idx ON climate.measurement_12_013 USING btree (station_id); CREATE INDEX measurement_12_013_y_idx ON climate.measurement_12_013 USING btree (date_part('year'::text, taken)); (Foreign key constraints to be added later.) The following query runs abysmally slow due to a full table scan: SELECT count(1) AS measurements, avg(m.amount) AS amount FROM climate.measurement m WHERE m.station_id IN ( SELECT s.id FROM climate.station s, climate.city c WHERE -- For one city ... -- c.id = 5182 AND -- Where stations are within an elevation range ... -- s.elevation BETWEEN 0 AND 3000 AND 6371.009 * SQRT( POW(RADIANS(c.latitude_decimal - s.latitude_decimal), 2) + (COS(RADIANS(c.latitude_decimal + s.latitude_decimal) / 2) * POW(RADIANS(c.longitude_decimal - s.longitude_decimal), 2)) ) <= 50 ) AND -- -- Begin extracting the data from the database. -- -- The data before 1900 is shaky; insufficient after 2009. -- extract( YEAR FROM m.taken ) BETWEEN 1900 AND 2009 AND -- Whittled down by category ... -- m.category_id = 1 AND m.taken BETWEEN -- Start date. (extract( YEAR FROM m.taken )||'-01-01')::date AND -- End date. Calculated by checking to see if the end date wraps -- into the next year. If it does, then add 1 to the current year. -- (cast(extract( YEAR FROM m.taken ) + greatest( -1 * sign( (extract( YEAR FROM m.taken )||'-12-31')::date - (extract( YEAR FROM m.taken )||'-01-01')::date ), 0 ) AS text)||'-12-31')::date GROUP BY extract( YEAR FROM m.taken ) The sluggishness comes from this part of the query: m.taken BETWEEN /* Start date. */ (extract( YEAR FROM m.taken )||'-01-01')::date AND /* End date. Calculated by checking to see if the end date wraps into the next year. If it does, then add 1 to the current year. */ (cast(extract( YEAR FROM m.taken ) + greatest( -1 * sign( (extract( YEAR FROM m.taken )||'-12-31')::date - (extract( YEAR FROM m.taken )||'-01-01')::date ), 0 ) AS text)||'-12-31')::date The HashAggregate from the plan shows a cost of 10006220141.11, which is, I suspect, on the astronomically huge side. There is a full table scan on the measurement table (itself having neither data nor indexes) being performed. The table aggregates 237 million rows from its child tables. Question What is the proper way to index the dates to avoid full table scans? Options I have considered: GIN GiST Rewrite the WHERE clause Separate year_taken, month_taken, and day_taken columns to the tables What are your thoughts? Thank you!

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  • Search 2 Columns with 1 Input Field

    - by Norbert
    I have a db with two columns: first name and last name. The first name can have multiple words. Last name can contain hyphenated words. Is there a way to search both columns with only one input box? Database ID `First Name` `Last Name` 1 John Peter Doe 2 John Fubar 3 Michael Doe Search john peter returns id 1 john returns id 1,2 doe returns id 1,3 john doe returns id 1 peter john returns id 1 peter doe returns id 1 doe john returns id 1 I previously tried the following. Searching for John Doe: SELECT * FROM names WHERE ( `first` LIKE '%john%' OR `first` LIKE '%doe%' OR `last` LIKE '%john%' OR `last` LIKE '%doe%' ) which returns both 1 and 3

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  • Round date to fiscal year

    - by Dave Jarvis
    The following database view rounds the date back to the closest fiscal year (April 1st): CREATE OR REPLACE VIEW FISCAL_YEAR_VW AS SELECT CASE WHEN to_number(to_char( SYSDATE, 'MM' )) < 4 THEN to_date('1-APR-'||to_char(add_months(SYSDATE, -12), 'YYYY'), 'dd-MON-yyyy') ELSE to_date('1-APR-'||to_char(SYSDATE, 'YYYY'), 'dd-MON-yyyy') END AS fiscal_year FROM dual; This allows us to calculate the current fiscal year based on today's date. How can this calculation be simplified or optimized?

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  • What are the disadvantages of VistaDB

    - by PhantomTypist
    I am looking into using a lightweight serverless database engine like SQLite, Firebird, or VistaDB in an upcoming project. Someone asked about What are the advantages of VistaDB. I would like to know what are the disadvantages of using VistaDB versus other technology?

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  • C# : DBConnection.Open() timeout is too long.

    - by leo
    Hi, I'm trying to connect to a server that the user inputs. When the server doesn't exist, I'd like to give a quick feedback to the end-user so he can correct what he's typed. Is there any way to test if a server exists before trying to connect ? Thanks

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  • Analysis services with non normalized table

    - by Uwe
    I have a table with several million rows. Each row represents a user session. There is a column called user which is not unique. There can be multiple sessions per user. I want to use Analysis services to get me the additional properties per user. Example: How many users (unique!) had a session longer than x minutes. How is that possible without changing the database. Note: there is no lookup-table and I cannot create one. What I am able of at the moment is to ask how many sessions were longer then x minutes.

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  • Insert Data from to a table

    - by Lee_McIntosh
    I have a table that lists number of comments from a particular site like the following: Date Site Comments Total --------------------------------------------------------------- 2010-04-01 00:00:00.000 1 5 5 2010-04-01 00:00:00.000 2 8 13 2010-04-01 00:00:00.000 4 2 7 2010-04-01 00:00:00.000 7 13 13 2010-04-01 00:00:00.000 9 1 2 I have another table that lists ALL sites for example from 1 to 10 Site ----- 1 2 ... 9 10 Using the following code i can find out which sites are missing entries for the previous month: SELECT s.site from tbl_Sites s EXCEPT SELECT c.site from tbl_Comments c WHERE c.[Date] = DATEADD(mm, DATEDIFF(mm, 0, GetDate()) -1,0) Producing: site ----- 3 5 6 8 10 I would like to be able to insert the missing sites that is listed from my query into the comments table with some default values, i.e '0's Date Site Comments Total --------------------------------------------------------------- 2010-04-01 00:00:00.000 3 0 0 2010-04-01 00:00:00.000 5 0 0 2010-04-01 00:00:00.000 6 0 0 2010-04-01 00:00:00.000 8 0 0 2010-04-01 00:00:00.000 10 0 0 the question is, how did i update/insert the table/values? cheers, Lee

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  • Merging sql queries to get different results by date

    - by pedalpete
    I am trying to build a 'recent events' feed and can't seem to get either my query correct, or figure out how to possible merge the results from two queries to sort them by date. One table holds games/, and another table holds the actions of these games/. I am trying to get the recent events to show users 1) the actions taken on games that are publicly visible (published) 2) when a new game is created and published. So, my actions table has actionId, gameid, userid, actiontype, lastupdate My games table has gameid, startDate, createdby, published, lastupdate I currently have a query like this (simplified for easy understanding I hope). SELECT actionId, actions.gameid, userid, actiontype, actions.lastupdate FROM actions JOIN ( SELECT games.gameid, startDate, createdby, published, games.lastupdate FROM games WHERE published=1 AND lastupdate>today-2 ) publishedGames on actions.gameid=games.gameid WHERE actions.type IN (0,4,5,6,7) AND actions.lastupdate>games.lastupdate and published=1 OR games.lastupdate>today-2 AND published=1 This query is looking for actions from published games where the action took place after the game was published. That pretty much takes care of the first thing that needs to be shown. However, I also need to get the results of the SELECT games.gameid, startDate, createdby, published, games.lastupdate FROM games WHERE published=1 AND startDate>today-2 so I can include in the actions list, when a new game has been published. When I run the query as I've got it written, I get all the actionids, and their gameids, but I don't get a row which shows the gameid when it was published. I understand that it may be possible that I need to run two seperate queries, and then somehow merge the results afterword with php, but I'm completely lost on where to start with that as well.

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  • MS ACCESS: How can i count distinct value using access query?

    - by Sadat
    here is the current complex query given below. SELECT DISTINCT Evaluation.ETCode, Training.TTitle, Training.Tcomponent, Training.TImpliment_Partner, Training.TVenue, Training.TStartDate, Training.TEndDate, Evaluation.EDate, Answer.QCode, Answer.Answer, Count(Answer.Answer) AS [Count], Questions.SL, Questions.Question FROM ((Evaluation INNER JOIN Training ON Evaluation.ETCode=Training.TCode) INNER JOIN Answer ON Evaluation.ECode=Answer.ECode) INNER JOIN Questions ON Answer.QCode=Questions.QCode GROUP BY Evaluation.ETCode, Answer.QCode, Training.TTitle, Training.Tcomponent, Training.TImpliment_Partner, Training.Tvenue, Answer.Answer, Questions.Question, Training.TStartDate, Training.TEndDate, Evaluation.EDate, Questions.SL ORDER BY Answer.QCode, Answer.Answer; There is an another column Training.TCode. I need to count distinct Training.TCode, can anybody help me? If you need more information please let me know

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  • How to efficiently SELECT rows from database table based on selected set of values

    - by Chau Chee Yang
    I have a transaction table of 1 million rows. The table has a field name "Code" to keep customer's ID. There are about 10,000 different customer code. I have an GUI interface allow user to render a report from transaction table. User may select arbitrary number of customers for rendering. I use IN operator first and it works for few customers: SELECT * FROM TRANS_TABLE WHERE CODE IN ('...', '...', '...') I quickly run into problem if I select few thousand customers. There is limitation using IN operator. An alternate way is create a temporary table with only one field of CODE, and inject selected customer codes into the temporary table using INSERT statement. I may then using SELECT A.* FROM TRANS_TABLE A INNER JOIN TEMP B ON (A.CODE=B.CODE) This works nice for huge selection. However, there is performance overhead for temporary table creation, INSERT injection and dropping of temporary table. Do you aware of better solution to handle this situation?

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  • ISBNdb Retrieving and Managing Info

    - by Pierre Sylvestre
    Given a set of databases how can one you get information on a book with given price first (which consist of the average of a hidden list of prices coming from different web site) and followed by an optional second option that shows the list of the different web site with their page? To take an example given a query for ISBN 9785554443331 - it returns "Chemistry the central science 11 edition" : new:$50 used good condition:$35 used poor condition:$20 If the return does not match with our product list an option to "click here to visit our partner" appears and which returns: Atextbook: $10 Btextbook: $10 Ctextbook: $9 Dtextbook: $8.50 I understand that the first search would be done simultaneous on the web and our database to determine whether or not we have the book and the web to get the average of the price of a given list of web site. Thank you in advance for the help

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  • SQLite long to wide formats?

    - by Stephen
    Hi, I wonder if there is a canonical way to convert data from long to wide format in SQLite (is that operation usually in the domain of relational databases?). I tried to follow this example for MySQL but I guess SQLite does not have the same IF construct... Thanks!

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  • To log in stored procedures?

    - by hgulyan
    If you have a long running SP, do you log somehow it's actions or just wait for this message? "Command(s) completed successfully." I assume, that there can be plenty solutions on this subject, but is there any best practice - a simple solution that is frequently used?

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