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• How to do left joins with least-n-per-group query?

  - by Nate

  I'm trying to get a somewhat complicated query working and am not having any luck whatsoever. Suppose I have the following tables: cart_items: +--------------------------------------------+ | item_id | cart_id | movie_name | quantity | +--------------------------------------------+ | 0 | 0 | braveheart | 4 | | 1 | 0 | braveheart | 9 | | . | . | . | . | | . | . | . | . | | . | . | . | . | | . | . | . | . | +--------------------------------------------+ movies: +------------------------------+ | movie_id | movie_name | ... | +------------------------------+ | 0 | braveheart | . | | . | . | . | | . | . | . | | . | . | . | | . | . | . | +------------------------------+ pricing: +-----------------------------------------+ | id | movie_name | quantity | price_per | +-----------------------------------------+ | 0 | braveheart | 1 | 1.99 | | 1 | braveheart | 2 | 1.50 | | 2 | braveheart | 4 | 1.25 | | 3 | braveheart | 8 | 1.00 | | . | . | . | . | | . | . | . | . | | . | . | . | . | | . | . | . | . | | . | . | . | . | +-----------------------------------------+ I need to join the data from the tables, but with the added complexity that I need to get appropriate price_per from the pricing table. Only one price should be returned for each cart_item, and that should be the lowest price from the pricing table where the quantity for the cart item is at least the quantity in the pricing table. So, the query should return for each item in cart_items the following: +---------------------------------------------+ | item_id | movie_name | quantity | price_per | +---------------------------------------------+ Example 1: Variable passed to the query: cart_id = 0. Return: +---------------------------------------------+ | item_id | movie_name | quantity | price_per | +---------------------------------------------+ | 0 | braveheart | 4 | 1.25 | | 1 | braveheart | 9 | 1.00 | +---------------------------------------------+ Note that this is a minimalist example and that additional data will be pulled from the tables mentioned (particularly the movies table). How could this query be composed? I have tried using left joins and subqueries, but the difficult part is getting the price and nothing I have tried has worked. Thanks for your help. EDIT: I think this is similar to what I have working with my "real" tables: SELECT t1.item_id, t2.movie_name, t1.quantity FROM cart_items t1 LEFT JOIN movies t2 ON t2.movie_name = t1.movie_name WHERE t1.cart_id = 0 Assuming I wrote that correctly (I quickly tried to "port over" my real query), then the output would currently be: +---------------------------------+ | item_id | movie_name | quantity | +---------------------------------+ | 0 | braveheart | 4 | | 1 | braveheart | 9 | +---------------------------------+ The trouble I'm having is joining the price at a certain quantity for a movie. I simply cannot figure out how to do it.

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• How can I LIMIT rows updates in MySQL if more than one table is involved?

  - by Taz

  I am trying to run an UPDATE query UPDATE ner.nerdataset, ner.shortabstracts SET ner.nerdataset.ShortAbstract=ner.shortabstracts.ShortAbstract WHERE ner.shortabstracts.Resource=ner.nerdataset.ResourceURI LIMIT 10; As MySQL does not allow the use of LIMIT when more than one table is involved in UPDATE what else can be done to limit this?

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• .NET Migrations Engine

  - by Karl Seguin

  I was once under the belief that Microsoft was working on an official, ruby-like, Migration framework. However, I haven't been able to find any additional information (or even the original source of my belief). Does anyone know any information about an official migration framework? or possibly an open source one?

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• Correct Sql Script for Formula

  - by Madan Madan

  Can anyone help me write SQL script for the following formula? If DEP = 1 If DROP 1 PLV = 334.86 * exp(0.3541 * ACTIVE_DAYS) + 0.25 * DROP + 20 * DEP Else If DROP < 0 PLV = DROP + 70 * ACTIVE_DAYS Else PLV = 0.25 * DROP + 70 * ACTIVE_DAYS The SQL script which I have is the following SELECT IF(dep=1, if(dep=1, (334.86 * exp(0.3541 * act_days)) + (0.25 * 'drop') + (20 * dep), if('drop'<0, 'drop' + (70 * act_days), (0.25 * 'drop') + (70 * act_days))),'0') as PLV But the above query is not right as something is missing where the formula says Else PLV = 0.26 * DROP Thanks,

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• Using NVL function in SQL, please help!

  - by user363024

  I'm needing to select first and last name in a table which is working fine in the following SQL, but the part that isn't working is the NVL function. The file should show all pilots at a company that fly helicopters and IF they don't have a licence the field HT_NAME should come up as 'N/A' and the field for end hours flown should be 0. I've put NVL function in as my text details but it still isn't working. Have i made a syntax error? Help would be appreciated. Select E.EMP_NBR, E.EMP_FIRSTNAME || ' ' || E.EMP_LASTNAME, E.EMP_PILOT, ED.HT_NBR, NVL(HT.HT_NAME, 'N/A'), NVL(ED.END_HRS_FLOWN, 0), ED.END_LAST_ANNUAL_REVIEW_DATE From ENDORSEMENT ED, EMPLOYEE E, HELICOPTER_TYPE HT WHERE HT.HT_NBR = ED.HT_NBR (+) ORDER BY ED.END_HRS_FLOWN DESC, E.EMP_FIRSTNAME || ' ' || E.EMP_LASTNAME ASC; should make employees who are not pilots appear with a N/A under heli type and 0 under hours flown. It isn't working - even though I have tried multiple things to repair it.

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• how to create ODBC Data source for a SQL Server 2008 on another machine?

  - by 5YrsLaterDBA

  I was able to create an ODBC Data Source locally for my SQL Server 2008. Now I moved to anohter machine and want to connect from the new machine to that SQL Server 2008. I know by default the SQL Server 2008 will not listen for the remote connection. I have enabled its Browser and TCP/IP. Error window is like this:

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• php connecting to mysql server(localhost) very slow

  - by Ahmad

  actually its little complicated: summary: the connection to DB is very slow. the page rendering takes around 10 seconds but the last statement on the page is an echo and i can see its output while the page is loading in firefox (IE is same). in google chrome the output becomes visible only when the loading finishes. loading time is approximately the same across browsers. on debugging i found out that its the DB connectivity that is creating problem. the DB was on another machine. to debug further. i deployed the DB on my local machine .. so now the DB connection is at 127.0.0.1 but the connectivity still takes long time. this means that the issue is with APACHE/PHP and not with mysql. but then i deployed my code on another machine which connects to DB remotely.and everything seems fine. basically the application uses couple of mod_rewrite.. but i removed all the .htaccess files and the slow connectivity issue remains.. i installed another APACHE on my machine and used default settings. the connection was still very slow. i added following statements to measure the execution time $stime = microtime(); $stime = explode(" ",$stime); $stime = $stime[1] + $stime[0]; // my code -- it involves connection to DB $mtime = microtime(); $mtime = explode(" ",$mtime); $mtime = $mtime[1] + $mtime[0]; $totaltime = ($mtime - $stime); echo $totaltime; the output is 0.0631899833679 but firebug Net panel shows total loading time of 10-11 seconds. same is the case with google chrome i tried to turn off windows firewall.. connectivity is still slow and i just can't quite find the reason.. i've tried multiple DB servers.. multiple apaches.. nothing seems to be working.. any idea of what might be the problem?

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• Physically cluster a MYSQL table for better performance

  - by ming yeow

  I have a 30M row table, which is indexed by ID now. However, a lot of the requests are around a much smaller subset, which is identified by app_user=1 Does it make sense to physically cluster the table according to this? If so, how can I do so?

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• Multiple has_many's of the same model

  - by Koning Baard

  I have these models: Person has_many :messages_form_person, :foreign_key => :from_user_id, :class_name => :messages has_many :messages_to_person, :foreign_key => :to_user_id, :class_name => :messages Message belongs_to :to_person, :foreign_key => :to_user_id, :class_name => :person belongs_to :from_person, :foreign_key => :to_user_id, :class_name => :person And this view: person#show <% @person.messages_to_person.each do |message| %> <%=h message.title %> <% end %> But I get this error: TypeError in People#show Showing app/views/people/show.html.erb where line #26 raised: can't convert Symbol into String Extracted source (around line #26): 23: <%=h @person.biography %> 24: </p> 25: 26: <% @person.messages_to_person.each do |message| %> 27: 28: <% end %> 29: I basicly want that people can send eachother messages. Can anyone help me? Thanks.

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• ROWID (oracle) - any use for it ?

  - by trojanwarrior3000

  My understanding is that ROWID is a unique value for each row in the result returned by a query. why we need this ROWID ?( there is already ROWNUM is ORACLE). Have any one used ROWID in sql query?

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• How do i get the data from a surveillance camera to a storage i can stream from?

  - by radbyx

  Hi my sisters house was robbed chrismas evening :( I talked with her about making a surveillance system for her. The idea is to have a system that detects intruders and then send a SMS to you while streaming it to a private website. The hard part: How and where do I storage the data from the camera so it's streamable? I think i can manage to do the streaming, website and SMS server, but i need the data (fundamentation). Thanks, any help is much appriciated.

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• How to prepare Cyrilic and other variables for storing into MySql DB? (PHP)

  - by Ole Jak

  How to prepare Cyrilic and other variables for storing into MySql DB? (PHP) So I need realy simple way to prepare recived from browser $_GET[string] variables for storing into DB. How to do such thing?

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• many-to-many-to-many, incl alignment of data from diff sources

  - by JefeCoon

  Re-factoring dbase to support many:many:many. At the second and third levels we need to preserve end-user 'mapping' or aligning of data from different sources, e.g. Order 17 FirstpartyOrderID => aha LineItem_for_BigShinyThingy => AA-1 # maps to 77-a LineItem_for_BigShinyThingy => AA-2 # maps to 77-b, 77-c LineItem_for_LittleWidget => AA-x # maps to 77-zulu, 77-alpha, 99-foxtrot LineItem_for_LittleWidget => AA-y # maps to 77-zulu, 99-foxtrot LineItem_for_LittleWidget => AA-z # maps to 77-alpha ThirdpartyOrderID => foo LineItem_for_BigShinyThingy => 77-a LineItem_for_BigShinyThingy => 77-b LineItem_for_BigShinyThingy => 77-c LineItem_for_LittleWidget => 77-zulu LineItem_for_LittleWidget => 77-alpha ThirdpartyOrderID => bar LineItem_for_LittleWidget => 99-foxtrot Each LineItem has daily datapoints reported from its own source (Firstparty|Thirdparty). In our UI & app we provide tools to align these, then we'd like to save them into the cleanest possible schema for querying, enabling us to diff the reported daily datapoints, and perform other daily calculations (which we'll store in the dbase also, fortunately that should be cake once we've nailed this). We need to map related [firstparty|thirdparty]line_items which have their own respective datapoints. We'll be using the association to pull each line_items collection of datapoints for summary and discrepancy calculations. I'm considering two options, std has_many,through x2 --or-- possibly (scary) ubermasterjoin table OptionA: order<<-->> order_join_table[id,order_id,firstparty_order_id,thirdparty_order_id] <<-->>line_item order_join_table[firstparty_order_id]-->raw_order[id] order_join_table[thirdparty_order_id]-->raw_order[id] raw_order-->raw_line_items[raw_order_id] line_item<<-->> line_item_join[id,LI_join_id,firstparty_LI,thirdparty_LI <<-->>raw_line_items line_item_join[firstparty_LI]-->raw_line_item[id] line_item_join[thirdparty_LI]-->raw_line_item[id] raw_line_item<<-->>datapoints = we rely upon join to store all mappings of first|third orders & line_items = keys to raw_* enable lookup of these order & line_item details = concerns about circular references and/or lack of correct mapping logic, e.g order--line_item--raw_line_items vs. order--raw_order--raw_line_items OptionB: order<<-->> join_master[id,order_id,FP_order_id,TP_order_id,FP_line_item_id,TP_line_item_id] join_master[FP_order_id & TP_order_id]-->raw_order[id] join_master[FP_line_item_id & TP_line_item_id]-->raw_line_item[id] = every combo of FP_line_item + TP_line_item writes a record into the join_master table = "theoretically" queries easy/fast/flexible/sexy At long last, my questions: a) any learnings from painful firsthand experience about how best to implement/tune/optimize many-to-many-to-many relationships b) in rails? c) any painful gotchas (circular references, slow queries, spaghetti-monsters) to watch out for? d) any joy & goodness in Rails3 that makes this magically easy & joyful? e) anyone written the "how to do many-to-many-to-many schema in Rails and make it fast & sexy?" tutorial that I somehow haven't found? If not, I'll follow up with our learnings in the hope it's helpful.. Thanks in advance- --Jeff

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• Transaction within transaction

  - by user281521

  Hello, I want to know if open a transaction inside another is safe and encouraged? I have a method: def foo(): session.begin try: stuffs except Exception, e: session.rollback() raise e session.commit() and a method that calls the first one, inside a transaction: def bar(): stuffs try: foo() #<<<< there it is :) stuffs except Exception, e: session.rollback() raise e session.commit() if I get and exception on the foo method, all the operations will be rolled back? and everything else will work just fine? thanks!!

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• SQL - How to display the students with the same age?

  - by Cristian

  the code I wrote only tells me how many students have the same age. I want their names too... SELECT YEAR(CURRENT DATE-DATEOFBIRTH) AS AGE, COUNT(*) AS HOWMANY FROM STUDENTS GROUP BY YEAR(CURRENT DATE-DATEOFBIRTH); this returns something like this: AGE HOWMANY --- ------- 21 3 30 5 Thank you. TABLE STUDENTS COLUMNS: StudentID (primary key), Name(varchar), Firstname(varchar), Dateofbirth(varchar) I was thinking of maybe using the code above and somewhere add the function concat that will put the stundents' names on the same row as in

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• Zend Framework Relations vs. Table Select

  - by rtmilker

  Hey! I just want to know your guys opinion on using join tables within the zend framework. Of course you can use relations by defining a referenceMap and dependentTables and stuff, or using setIntegrityCheck(false) within a db select(). The setIntegrityCheck version seems a little bit dirty to me, but the other version is not very suitable for big querys and joining many tables... I'm a PHP developer for 5 years now and new to the zend framework and just want get a direction for my first project. Thanks!!!

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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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• Restating a primary key to identify an employee

  - by George

  Our company decided to designate a contractor by adding an "X" in front of the employee number. But they aren't doing this in all systems. Is this a dangerous thing to do and why?

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• PHP - Drilling down Data and Looping with Loops

  - by stogdilla

  I'm currently having difficulty finding a way of making my loops work. I have a table of data with 15 minute values. I need the data to pull up in a few different increments $filters=Array('Yrs','Qtr','Day','60','30','15'); I think I have a way of finding out what I need to be able to drill down to but the issue I'm having is after the first loop to cycle through all the Outter most values (ex: the user says they want to display by Hours, each hour should be able to have a "+" that will then add a new div to display the half hour data, then each half hour data have a "+" to display the 15 minute data upon request. Now I can just program the number of outputs for each value (6 different outputs) just in-case... but isn't there a way I can make it do the drill down for each one in a loop? so I only have to code one output once and have it just check if there are any more intervals after it and check for those? I'm sure I'm just overlooking some very simple way of doing this but my brain isn't being clever today. Sorry in advance if this is a simple solution. I guess the best way I could think of it as a reply on a form. How you would check to see if it's a reply of a reply, and then if that reply has any replys...etc for output. Can anyone help or at least point me in the right direction? Or am I stuck coding each possible check? Thanks in advance!

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• need help with a simple SQL update statement.

  - by Tony

  There's a field with type of varchar. It actually stores a float point string. Like 2.0 , 12.0 , 34.5 , 67.50 ... What I need is a update statement that remove the ending zeros of fields like 2.0 , 12.0 , change them to their integer representation , that is 2 , 12 ...,and leave 3.45 , 67.50 unchanged . How should I do this ? I am using oracle 10.

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• Dmbedded couchDB

  - by Chang

  CouchDB is great, I like its replication functionality, but it's a bit larger and slower when used in desktop application. As I tested in intel duo core cpu, 12 seconds to load 10000 docs 10 seconds to insert 10000 doc, but need 20 seconds to update view, so total is 30 seconds Is there any No SQL implementation which has the same replication functionality, but the size is very small, and the speed is quite good( 1 second to load 10000 docs). Thanks

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• How Can I Join Two DB Tables and Return Lowest Price From Joined Table

  - by Jason

  I have two tables, the first table has the product and the second table the prices. The price table could have more than one price per product but I only want to display the lowest. But I keep getting all the prices returned and I'm having trouble figuring out how to do it. this is what I get returned in my query: SELECT * FROM products AS pr JOIN prices AS p ON pr.id = p.product_id WHERE pr.live = 1 AND p.live = 1 id product1 name description £100 id product1 name description £300 id product1 name description £200 id product2 name description £50 id product2 name description £80 id product2 name description £60 id product3 name description £222 id product3 name description £234 id product3 name description £235 but I'm after: id product1 name description £100 id product2 name description £50 id product3 name description £222 Any help would be appreciated

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• how to join 3 relational tables

  - by orioncabbar

  Hello there, how to join 3 relational tables with the structure: t1 | id t2 | id | rating t3 | source_id | relation t3 stores the data of a field which t1 and t2 uses both. so source_id field can be t1's id or t2's id. input : t1 id output : t2 rating an example: **t1** id | --------- 42 | **t2** id | rating ------------- 37 | 9.2 **t3** id | source_id -------------- 42 | 1 37 | 1 26 | 2 23 | 1 what i want is to get 9.2 output with 42 input. can you do that in one sql query?

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• Inheritance in tables - structure problem

  - by Naor

  I have 3 types of users in my system. each type has different information I created the following tables: BaseUser(base_user_id, username, password, additional common data) base_user_id is PK and Identity UserType1(user_id, data related to type1 only) user_id is PK and FK to base_user_id UserType2(user_id, data related to type2 only) user_id is PK and FK to base_user_id UserType3(user_id, data related to type3 only) user_id is PK and FK to base_user_id Now I have relation from each type of user to warehouses table. Users from type1 and type2 should have only warehouse_id and users from type3 should have warehouse_id and customer_id. I thought about this structure: WarehouseOfUser(base_user_id,warehouse_id) base_user_id is FK to base_user_id in BaseUser WarehouseOfTyp3User(base_user_id,warehouse_id, customer_id) base_user_id is FK to base_user_id in BaseUser The problem is that such structure allows 2 things I want to prevent: 1. add to WarehouseOfTyp3User data of user from type2 or type1. 2. add to WarehouseOfUser data of user from type3. what is the best structure for such case?

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• How to prompt user input parameters for SQL Queries in Access 2010

  - by user1848907

  SELECT Transactions.TransactionNumber FROM Transactions WHERE (((Transactions.Date)>=#11/23/12#)) AND (((Transactions.Date)<=#11/23/12#)); The above code returns all the transaction that happened between the specified dates. But I want those dates to be defined by the user every time the query is executed. I tried using the [] operators to have the user define the criteria in the WHERE, something like this: WHERE (((Transactions.Date)>=[Input a Date])) AND (((Transactions.Date)<=[Input a Date])); But microsoft Access throws a Syntax error message. The same happens when I include the # (date operators) like this WHERE (((Transactions.Date)>=#[Input a Date]#)) AND (((Transactions.Date)<=#[Input a Date]#)); Is there anopther way to manage dates that I'm not aware of or is asking a user for dates in a query out of the question

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