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• which is better, creating a view or a new table?

  - by Carson

  I have some demanding mysql queries that are needed to grap same datasets from several mysql tables. I am thinking of creating a table or 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 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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• "Othello" game needs some clarification

  - by pappu

  I am trying to see if my understanding of "othello" fame is correct or not. According to the rules, we flip the dark/light sides if we get some sequence like X000X = XXXXX. The question I have is if in the process of flipping 0-X or X- 0, do we also need to consider the rows/columns/diagonals of newly flipped elements? e.g. consider board state as shown in above image(New element X is placed @ 2,3) When we update board, we mark elements from 2,3 to 6,3 as Xs but in this process elements like horizontal 4,3 to 4,5 and diagonal 2,3 to 4,5 are also eligible for update? so do we update those elements as well? or just the elements which have starting as 2,3 (i.e update rows/column/diagonal whose starting point is the element we are dealing with, in our case 2,3?) Please help me understand it

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• Very basic database theory.

  - by John R

  I have a set of tables to show the relationship between organziations and supporters below. Although I have done some basic mySQL querries, I know very little about database 'design'. I plan to querry the database for: -a list of contributors to a specific organization... or, -a list of organizations that a specific suporter supports. The database tables for organiations and contributors may have other columns in the future and recieve a lesser amount of querries based on that information. A | X A | Y A | Z B | X B | Y C | X C | Z How should the tables be set up? I assume that there should be a third table, but there is still redundent information in the third table. Is there a better way of setting up the tables? +----+-------+ +-------------+----------+ +----+-------+ | id | org | | org | contr | | id | contr.| +----+-------+ +-------------+----------+ +----+-------+ | 1 | A | | 1 | 1 | | 1 | X | | 2 | B | | 1 | 2 | | 2 | Y | | 3 | C | | 1 | 3 | | 3 | Z | +----+-------+ | 2 | 1 | +----+-------+ | 2 | 2 | | 3 | 1 | | 3 | 3 | +-------------+----------+

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• Can I force MySQL to output results before query is completed?

  - by Gordon Royle

  I have a large MySQL table (about 750 million rows) and I just want to extract a couple of columns. SELECT id, delid FROM tbl_name; No joins or selection criteria or anything. There is an index on both fields (separately). In principle, it could just start reading the table and spitting out the values immediately, but in practice the whole system just chews up memory and basically grinds to a halt. It seems like the entire query is being executed and the output stored somewhere before ANY output is produced... I've searched on unbuffering, turning off caches etc, but just cannot find the answer. (mysqldump is almost what I want except it dumps the whole table - but at least it just starts producing output immediately)

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• how to get unique values set from a repeating values list

  - by Mariselvam

  I need to parse a large log file (flat file), which contains two column of values (column-A , column-B). Values in both columns are repeating. I need to find for each unique value in column-A , I need to find a set of column-B values. Is this can be done using unix shell command or need to write any perl or python script? What are the ways this can be done? Example: xxxA 2 xxxA 1 xxxB 2 XXXC 3 XXXA 3 xxxD 4 output: xxxA - 2,1,3 xxxB - 2 xxxC - 3 xxxD - 4

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• Subquery vs Traditional join with WHERE clause?

  - by BradC

  When joining to a subset of a table, any reason to prefer one of these formats over the other? Subquery version: SELECT ... FROM Customers AS c INNER JOIN (SELECT * FROM Classification WHERE CustomerType = 'Standard') AS cf ON c.TypeCode = cf.Code INNER JOIN SalesReps s ON cf.SalesRepID = s.SalesRepID vs the WHERE clause at the end: SELECT ... FROM Customers AS c INNER JOIN Classification AS cf ON c.TypeCode = cf.Code INNER JOIN SalesReps AS s ON cf.SalesRepID = s.SalesRepID WHERE cf.CustomerType = 'Standard' The WHERE clause at the end feels more "traditional", but the first is arguably more clear, especially as the joins get increasingly complex. Only other reason I can think of to prefer the second is that the "SELECT *" on the first might be returning columns that aren't used later (In this case, I'd probably only need to return cf.Code and Cf.SalesRepID)

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• Which index is used in select and why?

  - by Lukasz Lysik

  I have the table with zip codes with following columns: id - PRIMARY KEY code - NONCLUSTERED INDEX city When I execute query SELECT TOP 10 * FROM ZIPCodes I get the results sorted by id column. But when I change the query to: SELECT TOP 10 id FROM ZIPCodes I get the results sorted by code column. Again, when I change the query to: SELECT TOP 10 code FROM ZIPCodes I get the results sorted by code column again. And finally when I change to: SELECT TOP 10 id,code FROM ZIPCodes I get the results sorted by id column. My question is in the title of the question. I know which indexes are used in the queries, but my question is, why those indexes are used? I the second query (SELECT TOP 10 id FROM ZIPCodes) wouldn't it be faster if the clusteder index was used? How the query engine chooses which index to use?

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• Insert consecutive numbers

  - by Markus

  Hi. I have a table A (Acons, A1, A2, A3) in which I should insert information from another table B with columns (B1, B2, B3). The Acons is a column in which should contain some consecutive numbers (it is not an identity and I cannot make it identity). I know xmin - starting the from number the sequence has to be computed. How can I insert the rows into the table A, using a single Insert statement? I tried like the following, but it didn't work: DECLARE @i AS INT; SET @i = xmin; INSERT INTO A(Acons, A1, A2, A3) SELECT @i = (Bcons = (@i + 1)), B1, B2, B3 FROM B Unfortunatelly, the above solution does not work;

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• read contents of a sql table into a data grid view

  - by syedsaleemss

  Im using c# .net windows application form. i have created a database named "resources" in SQL server 2005. In that i have a table named "resourcetable" which has two columns. now i need to read the data in the table into a datagridview. I can do this by using the connection string and querry by giving the table name. But my problem is i have a button and if i click on that button, an open dialog box should open and i should be able to select a database amomng many databases and in that selected database i have to select one table amomg many tables. i.e select a table ofa particular database. and the contents of that table are to be displayed in a datagridview.

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• Conditional CellRenderCombo in pyGTK TreeView

  - by Präriewolf

  I have a two column TreeView attached to a ListStore. Both columns are CellRenderCombo combo boxes. When the user selects an entry in the first box, I need to dynamically load a set of options in the second. For example, the behavior I want is: On row 0, the user selects "Alphabet" in the first column box. The second column box is populated with the letters "A-Z". On row 1, the user selects "Numbers" in the first column box. The second column box is populated with the numbers "0-9". On row 2, the user selects "Alphabet" in the first column box. The second column box is populated with the letters "A-Z". etc. Does anyone know how to do this, or seen any open source pygtk or gtk projects that have similar behavior which I can analyze?

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• comparing two tables

  - by sza

  I have two identical table ie all the columns are identical and one of the datatype is Text, one is varchar(255) and the rest are int. Lets say the table name is 'AAAAA'. Table AAAAA was processed and backed up earlier this month. Both the tables were storing data and now the second table is only storing data. I need to find unmatching records from the second table (BBBBB) which is storing data right now and add those records to Table AAAAA. Your help will be highly appreciated. I tried to use 'EXCEPT' but it does not support text datatype. I'm using SQL Server 2005.

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• Doctrine: Mixing YAML markup and db manager (navicat) editing?

  - by ropstah

  I think the answer to this question should be: No. However I hope to be corrected. I'd like to edit our database using a mixture of YAML markup + Doctrine createTables() and Navicat editing. Can I maintain the inheritance which is marked up? Example (4 steps, at step 4, Doctrine is in no way able to re-create the inheritance schema... or is it?): Step 1: Create YAML with inheritance --- Entity: columns: username: string(20) password: string(16) created_at: timestamp updated_at: timestamp User: inheritance: extends: Entity type: column_aggregation keyField: type keyValue: 1 Group: inheritance: extends: Entity type: column_aggregation keyField: type keyValue: 2 Step 2: Create tables using Doctrine (and drop/create db if nessecary) Created sql: CREATE TABLE entity (id BIGINT AUTO_INCREMENT, username VARCHAR(20), password VARCHAR(16), created_at DATETIME, updated_at DATETIME, type VARCHAR(255), PRIMARY KEY(id)) ENGINE = INNODB Step 3: Edit table using Navicat Step 4: Refresh YAML file because of 'external' edits...

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• using regular expression / Remove special characters with linq to sql

  - by Prasad

  How can i use regular expressions with linq to sql in the asp.net mvc(C#) application? The columns in my MSSQL table (Products) has some special characters like (, - % ',.....). While searching for a product i need to search without that special chareters. For ex.: I have a product say (ABC-Camp's / One), when i search for "abccamp", it should pull the product. I am trying the query like: from p in _context.pu_Products where p.User_Id == userId && p.Is_Deleted == false && p.Product_Name.ToLower().Contains(text.ToLower()) select new Product { ProductId = p.Product_Id, ProductName = p.Product_Name.Replace("’", "").Replace("\"", ""), RetailPrice = p.Retail_Price ?? 0M, LotSize = p.Lot_Size > 0 ? p.Lot_Size ?? 1 : 1, QuantityInHand = p.Quantity_In_Hand ?? 0 } But i need to search without any special characters...

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• Finding records within a 5 min time interval in SQL

  - by Mellonjollie

  I have a table with over 100,000 rows that contain the following columns: ID, Time, and Boolean. The time column tracks time down to the second. I need a query that will find all instances of Boolean = 1 for every 5 minute interval of time from the start of the table to the end, then group the count by time interval. The table represents 4 hours of data, so I should get 48 rows of results. I'm using MS SQL Server. I've tried a few approaches, but the time interval logic is giving me a hard time.

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• Selecting data effectively sql

  - by learner135

  Hi, I have a very large table with over 1000 records and 200 columns. When I try to retreive records matching some criteria in the WHERE clause using SELECT statement it takes a lot of time. But most of the time I just want to select a single record that matches the criteria in the WHERE clause rather than all the records. I guess there should be a way to select just a single record and exit which would minimize the retrieval time. I tried ROWNUM=1 in the WHERE clause but it didn't really work cause I guess the engine still checks all the records even after finding the first record matching the WHERE criteria. Is there a way to optimize in case if I want to select just a few records? Thanks in advance. Edit: I am using oracle 10g.

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• I Need Help Fixing My Small Time Sheet Table - Relational DB - SQL Server

  - by user327387

  I have a TimeSheet table as: CREATE TABLE TimeSheet ( timeSheetID employeeID setDate timeIn outToLunch returnFromLunch timeOut ); Employee will set his/her time sheet daily, i want to ensure that he/she doesn't cheat. What should i do? Should i create a column that gets date/time of the system when insertion/update happens to the table and then compare the created date/time with the time employee's specified - If so in this case i will have to create date/time column for timeIn, outToLunch, returnFromLunch and timeOut. I don't know, what do you suggest? Note: i'm concerned about tracking these 4 columns timeIn, outToLunch, returnFromLunch and timeOut

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• MySQL ORDER BY returns things in (apparently) random order !?

  - by Luke H

  The following query: SELECT DISTINCT ClassName FROM SiteTree ORDER BY ClassName is returning things in no apparent order! I get the same result whether I quote column/table names, or use DISTINCT or not, or add ASC or DESC. I assumed the indexes might be broken, or something like this, so tried dropping and recreating. Also tried REPAIR TABLE and CHECK TABLE. The table collation is set to latin1_swedish_ci. All the textual columns are set to use UTF-8 and collation is set to utf8_general_ci What could be causing this?

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• ASP MVC ViewData from one view to another (Html.Encode())

  - by Jacob Huggart

  Hello all, I have a page with a bunch of labels and checkboxes on it. On this page, the labels need to be easily customizable after the project is deployed. So I made all of the labels in this style: Html.Encode(ViewData["lblText"]) And I added a button on the page called "Edit Button Labels" that will only be seen by admins. When that button is clicked, I would like to load another view that simply contains a table of two columns. One column needs to contain the current labels and the other should have text boxes for the user to enter new labels. Then, once any changes have been made, I need to permanently change the "lblText" for each label on the original page. I have tried passing viewdata and tempdata to the "Edit Button Labels" view using both return view() and return RedirectToAction() with no success. Am I missing something minor or is there a better way to do this?

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• Using Rails, how can I set my primary key to not be an integer-typed column?

  - by Rudd Zwolinski

  I'm using Rails migrations to manage a database schema, and I'm creating a simple table where I'd like to use a non-integer value as the primary key (in particular, a string). To abstract away from my problem, let's say there's a table employees where employees are identified by an alphanumeric string, e.g. "134SNW". I've tried creating the table in a migration like this: create_table :employees, {:primary_key => :emp_id} do |t| t.string :emp_id t.string :first_name t.string :last_name end What this gives me is what seems like it completely ignored the line t.string :emp_id and went ahead and made it an integer column. Is there some other way to have rails generate the PRIMARY_KEY constraint (I'm using PostgreSQL) for me, without having to write the SQL in an execute call? NOTE: I know it's not best to use string columns as primary keys, so please no answers just saying to add an integer primary key. I may add one anyway, but this question is still valid.

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• Where's the rest of the space used in this table?

  - by Eric H.

  I'm using SQL Server 2005. I have a table whose row size should be 124 bytes. It's all ints or floats, no NULL columns (so everything is fixed width). There is only one index, clustered. The fill factor is 0. After inserting a ton of data, sp_spaceused returns the following name rows reserved data index_size unused OHLC_Bar_Trl 117076054 29807664 KB 29711624 KB 92344 KB 3696 KB which shows a rowsize of approx (29807664*1024)/117076054 = 260 bytes/row. Where's the rest of the space? Is there some DBCC command I need to run to tighten up this table (I could not insert the rows in correct index order, so maybe it's just internal fragmentation)?

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• using dummy row with NOT NULL to solve DEFAUT NULL

  - by Tony38

  I know having DEFAULT NULLS is not a good practice but I have many optional lookup values which are FK in the system so to solve this issue here is what i am doing: I use NOT NULL for every FK / lookup valve field. I have the first row in every table which is PK id = 1 as a dummy row with just "none" in all the columns. this way I can use NOT NULL in my schema and if needed reference to the none row values which should be null. Is this a good design or any other work arounds?

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• rails summing column values of rows with similar attributes

  - by butterywombat

  Hi all, I have a Sites table that has columns name, and time. The name does not have to be unique. So for example I may have the entries 'hi.com, 5', 'hi.com, 10', 'bye.com, 4'. I would like to sum up all the unique sites so that i get 'hi.com, 15' and 'bye.com, 4' for plotting purposes. How can I do that? (For some reference I was looking at http://railscasts.com/episodes/223-charts but I couldn't get the following (translated to my table) to work def self.total_on(date) where("date(purchased_at) = ?", date).sum(:total_price) end nor do I really understand the syntax of the 'where("date(purchased_at) = ?", date)' part. Thanks for helping a rails newbie!

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• SQL Check Constraint cannot reference other column

  - by user1777711

  I trying to add this sql check in ALTER TABLE School add Role check_role CHECK (check_role IN ('Teaching Assistant', 'Lecturer', 'Professor')); I get the error below ERROR at line 3: ORA-02438: Column check constraint cannot reference other columns SQL> desc School; Name Null? Type ----------------------------------------- -------- ---------------------------- STAFFNUM NOT NULL VARCHAR2(12) NAME NOT NULL VARCHAR2(50) ADDRESS NOT NULL VARCHAR2(300) DOB DATE I am trying add a column call Role, with the check constraint check_role I am using Oracle SQL. Thanks for all help!

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• Computed Column with relationships

  - by Sethery

  I have a table, MapLocation, which has a column and two relationships with tables that have a field that really need to be displayed as a single concatenated value. I was thinking this was a perfect case for a computed column, but not sure how to go about it. MapLocation MaoNo Section _____________________ _____________________ _____________________ MapNoId MapNoId SectionId SectionId MapNumber (int) Section (int) Identifier (nvarchar) LocationName (nvarchar) LocationName = "MapNUmber - SectionNumber - Identifier" ex: 20 - 03 - SW4 How would I write that? I haven't done much with computed columns or concatenating in SQL. Edit: I need an actual computed column that is automatically updated, im looking for the formula. Or is this more of a function/trigger? Its possible, I certainly barely know what I'm doing. The idea is that I dont want to have to do two more server calls and concatenate these values client side.

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• Multiple column Union Query without duplicates

  - by Adam Halegua

  I'm trying to write a Union Query with multiple columns from two different talbes (duh), but for some reason the second column of the second Select statement isn't showing up in the output. I don't know if that painted the picture properly but here is my code: Select empno, job From EMP Where job = 'MANAGER' Union Select empno, empstate From EMPADDRESS Where empstate = 'NY' Order By empno The output looks like: EMPNO JOB 4600 NY 5300 MANAGER 5300 NY 7566 MANAGER 7698 MANAGER 7782 MANAGER 7782 NY 7934 NY 9873 NY Instead of 5300 and 7782 appearing twice, I thought empstate would appear next to job in the output. For all other empno's I thought the values in the fields would be (null). Am I not understanding Unions correctly, or is this how they are supposed to work? Thanks for any help in advance.

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