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• What is the simplest way to interpolate and lookup in an x,y table in excel?

  - by dassouki

  I would like to do a lookup and interpolation based on x, y data for the following table. I'd like the equation to be as simple as possible to reduce the amount of possible errors. The full table is about 50 rows x 30 columns. I have about 20 of those tables. Here is an extract from one: A B C D 1 0.1 0.2 0.3 2 2.4 450 300 50 3 2.3 500 375 52 4 2.1 550 475 55 5 1.8 600 600 60 For example, the equation should find the value for x = 2.27 and y = 0.15

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• long table in excel - how to produce stats for subtables?

  - by joe_shmoe

  Hi, (new to excel - ) say I have a table with columns A = {1..5}, B = {a..e} and Score = Number. I want to produce a new table that would display statistics for each A,B combination, e.g. A B Mean SD 1 a .. .. 1 b .. .. ... 2 a .. .. What's the best way of doing this? (i'm on office 2010 beta) Thanks a lot

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• How to edit the Boot Graphics Resource Table / Edit windows 8 BOOT LOGO?

  - by user144773

  I want to edit the screen which is displayed when windows 8 (starts) loads (/loading). As for now it has the Toshiba logo, I want my custom logo or the windows default logo. I have found that UEFI has something called "Boot Graphics Resource Table" and that it overides the default logo if there is a image present (source) How can I edit the logo stored in UEFI firmware or Boot Graphics Resource Table? if it's in the "bootres.dll", which does UEFI use? My disk (spread across a few system/usefi/windows/etc partitions) has around twenty bootres.dlls. The bootres.dll is signed by Microsoft, but I don't have to worry because I can sign the file I edit myself with my own certificate.

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• how to make Excel/Access data have more than one quantity in a table?

  - by Xrave

  Sorry for the confusing question, I'm not sure how to word it right: here's a mock sample of my data Name: Cheeseburger Date: 1/20/2011 Stock: 30 Price: 200 Name: Hamburger Date: 1/20/2011 Stock: 12 Price: 180 Name: Cheeseburger Date: 1/21/2011 Stock: 31 Price: 210 ... I will have to make a table in excel or access capable of looking up the stock and price trends of a particular brand through time. Trouble is, I have two independent variables (Stock, Price) and two known dependent variables (Name, Date). So, I cannot use a simple table where the x axis is the name, y axis is the time, and the cells represent a quantity - each cell have to represent two quantities (Stock, Price) Does anyone know how to do that? Thanks.

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• CSS: Chrome and Safari seem to 'add' border to width, while IE, Firefox & Opera don't

  - by Michiel

  Hey guys, I'm trying to achieve cross-browser consistency for my website, but I have been trying all day now and its driving me nuts (0.38 am here in Europe now..). It's about this page: http://www[insert-dot-here]geld[insert-dash-here]surfen[insert-dot-here]nl/uitbetalingen.html (please note that I prefer this URL not to be made crawlable for seo-bots) If you view this page in IE, Firefox or Opera, everything is fine, but in Chrome and Safari the tables are a little out of line (as you'll probably clearly notice). What seems to be the problem?; it appears to me that in Chrome and Safari the left and right border (2px) in total are added to the set table width, while in the other browsers the border is considered part of the width. The (most) relevant CSS-lines are the following ones (from the tabel.css-file, also available through the page's source file): table.uitbetaling { margin: 11px 18px 10px 19px; border: 1px solid #8ccaee; width: 498px; padding: 0; } table.uitbetaling img, table.uitbetaling td { margin: 0; border: 0; padding: 0; width: 496px; } table.uitbetaling tr { margin: 0; border: 0; padding: 0 1px 0 0; } So basically I have used a table-structure to organize images, like this; (the class of the table is 'uitbetaling') <table> <tr><td><img /></td></tr> <tr><td><img /></td></tr> ... <tr><td><img /></td></tr> </table> If, here, I set the width of 'table.uitbetaling' and 'table.uitbetaling img, table.uitbetaling td' to the same value (e.g. both 496 or 498), the 'problem' in Chrome and Safari is solved, however in Firefox the right side border is than blank. Because the right-side border can't 'fit' in anymore. 'img' and 'td' must be at least 2px more narrow than 'table.uitbetaling' for the right-border be visible in Firefox. Is there any way to solve this? Thanks so much in advance for your insights!!

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• OperationalError: foreign key mismatch

  - by Niek de Klein

  I have two tables that I'm filling, 'msrun' and 'feature'. 'feature' has a foreign key pointing to the 'msrun_name' column of the 'msrun' table. Inserting in the tables works fine. But when I try to delete from the 'feature' table I get the following error: pysqlite2.dbapi2.OperationalError: foreign key mismatch From the rules of foreign keys in the manual of SQLite: - The parent table does not exist, or - The parent key columns named in the foreign key constraint do not exist, or - The parent key columns named in the foreign key constraint are not the primary key of the parent table and are not subject to a unique constraint using collating sequence specified in the CREATE TABLE, or - The child table references the primary key of the parent without specifying the primary key columns and the number of primary key columns in the parent do not match the number of child key columns. I can see nothing that I'm violating. My create tables look like this: DROP TABLE IF EXISTS `msrun`; -- ----------------------------------------------------- -- Table `msrun` -- ----------------------------------------------------- CREATE TABLE IF NOT EXISTS `msrun` ( `msrun_name` VARCHAR(40) PRIMARY KEY NOT NULL , `description` VARCHAR(500) NOT NULL ); DROP TABLE IF EXISTS `feature`; -- ----------------------------------------------------- -- Table `feature` -- ----------------------------------------------------- CREATE TABLE IF NOT EXISTS `feature` ( `feature_id` VARCHAR(40) PRIMARY KEY NOT NULL , `intensity` DOUBLE NOT NULL , `overallquality` DOUBLE NOT NULL , `charge` INT NOT NULL , `content` VARCHAR(45) NOT NULL , `msrun_msrun_name` VARCHAR(40) NOT NULL , CONSTRAINT `fk_feature_msrun1` FOREIGN KEY (`msrun_msrun_name` ) REFERENCES `msrun` (`msrun_name` ) ON DELETE NO ACTION ON UPDATE NO ACTION); CREATE UNIQUE INDEX `id_UNIQUE` ON `feature` (`feature_id` ASC); CREATE INDEX `fk_feature_msrun1` ON `feature` (`msrun_msrun_name` ASC); As far as I can see the parent table exists, the foreign key is pointing to the right parent key, the parent key is a primary key and the foreign key specifies the primary key column. The script that produces the error: from pysqlite2 import dbapi2 as sqlite import parseFeatureXML connection = sqlite.connect('example.db') cursor = connection.cursor() cursor.execute("PRAGMA foreign_keys=ON") inputValues = ('example', 'description') cursor.execute("INSERT INTO `msrun` VALUES(?, ?)", inputValues) featureXML = parseFeatureXML.Reader('../example_scripts/example_files/input/featureXML_example.featureXML') for feature in featureXML.getSimpleFeatureInfo(): inputValues = (featureXML['id'], featureXML['intensity'], featureXML['overallquality'], featureXML['charge'], featureXML['content'], 'example') # insert the values into msrun using ? for sql injection safety cursor.execute("INSERT INTO `feature` VALUES(?,?,?,?,?,?)", inputValues) connection.commit() for feature in featureXML.getSimpleFeatureInfo(): cursor.execute("DELETE FROM `feature` WHERE feature_id = ?", (str(featureXML['id']),))

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• What's a clean way to break up a DataTable into chunks of a fixed size with Linq?

  - by Michael Haren

  Update: Here's a similar question Suppose I have a DataTable with a few thousand DataRows in it. I'd like to break up the table into chunks of smaller rows for processing. I thought C#3's improved ability to work with data might help. This is the skeleton I have so far: DataTable Table = GetTonsOfData(); // Chunks should be any IEnumerable<Chunk> type var Chunks = ChunkifyTableIntoSmallerChunksSomehow; // ** help here! ** foreach(var Chunk in Chunks) { // Chunk should be any IEnumerable<DataRow> type ProcessChunk(Chunk); } Any suggestions on what should replace ChunkifyTableIntoSmallerChunksSomehow? I'm really interested in how someone would do this with access C#3 tools. If attempting to apply these tools is inappropriate, please explain! Update 3 (revised chunking as I really want tables, not ienumerables; going with an extension method--thanks Jacob): Final implementation: Extension method to handle the chunking: public static class HarenExtensions { public static IEnumerable<DataTable> Chunkify(this DataTable table, int chunkSize) { for (int i = 0; i < table.Rows.Count; i += chunkSize) { DataTable Chunk = table.Clone(); foreach (DataRow Row in table.Select().Skip(i).Take(chunkSize)) { Chunk.ImportRow(Row); } yield return Chunk; } } } Example consumer of that extension method, with sample output from an ad hoc test: class Program { static void Main(string[] args) { DataTable Table = GetTonsOfData(); foreach (DataTable Chunk in Table.Chunkify(100)) { Console.WriteLine("{0} - {1}", Chunk.Rows[0][0], Chunk.Rows[Chunk.Rows.Count - 1][0]); } Console.ReadLine(); } static DataTable GetTonsOfData() { DataTable Table = new DataTable(); Table.Columns.Add(new DataColumn()); for (int i = 0; i < 1000; i++) { DataRow Row = Table.NewRow(); Row[0] = i; Table.Rows.Add(Row); } return Table; } }

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• How can I prevent segmentation faults in my program?

  - by worlds-apart89

  I have a C assignment. It is a lot longer than the code shown below, and we are given the function prototypes and instructions only. I have done my best at writing code, but I am stuck with segmentation faults. When I compile and run the program below on Linux, at "735 NaN" it will terminate, indicating a segfault occurred. Why? What am I doing wrong? Basically, the program does not let me access table-list_array[735]-value and table-list_array[735]-key. This is of course the first segfault. There might be more following index 735. #include <stdio.h> #include <stdlib.h> typedef struct list_node list_node_t; struct list_node { char *key; int value; list_node_t *next; }; typedef struct count_table count_table_t; struct count_table { int size; list_node_t **list_array; }; count_table_t* table_allocate(int size) { count_table_t *ptr = malloc(sizeof(count_table_t)); ptr->size = size; list_node_t *nodes[size]; int k; for(k=0; k<size; k++){ nodes[k] = NULL; } ptr->list_array = nodes; return ptr; } void table_addvalue(count_table_t *table) { int i; for(i=0; i<table->size; i++) { table->list_array[i] = malloc(sizeof(list_node_t)); table->list_array[i]->value = i; table->list_array[i]->key = "NaN"; table->list_array[i]->next = NULL; } } int main() { count_table_t *table = table_allocate(1000); table_addvalue(table); int i; for(i=0; i<table->size; i++) printf("%d %s\n", table->list_array[i]->value, table->list_array[i]->key); return 0; }

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• Spring's JdbcDaoSupport (using MySQL Connector/J) fails after executing sql that adds FK

  - by John

  I am using Spring's JdbcDaoSupport class with a DriverManagerDataSource using the MySQL Connector/J 5.0 driver (driverClassName=com.mysql.jdbc.driver). allowMultiQueries is set to true in the url. My application is an in-house tool we recently developed that executes sql scripts in a directory one-by-one (allows us to re-create our schema and reference table data for a given date, etc, but I digress). The sql scripts sometime contain multiple statements (hence allowMultiQueries), so one script can create a table, add indexes for that table, etc. The problem happens when including a statement to add a foreign key constraint in one of these files. If I have a file that looks like... --(column/constraint names are examples) CREATE TABLE myTable ( fk1 BIGINT(19) NOT NULL, fk2 BIGINT(19) NOT NULL, PRIMARY KEY (fk1, fk2) ); ALTER TABLE myTable ADD CONSTRAINT myTable_fk1 FOREIGN KEY (fk1) REFERENCES myOtherTable (id) ; ALTER TABLE myTable ADD CONSTRAINT myTable_fk2 FOREIGN KEY (fk2) REFERENCES myOtherOtherTable (id) ; then JdbcTemplate.execute throws an UncategorizedSqlException with the following error message and stack trace: Exception in thread "main" org.springframework.jdbc.UncategorizedSQLException: StatementCallback; uncategorized SQLException for SQL [ THE SQL YOU SEE ABOVE LISTED HERE ]; SQL state [HY000]; error code [1005]; Can't create table 'myDatabase.myTable' (errno: 150); nested exception is java.sql.SQLException: Can't create table 'myDatabase.myTable' (errno: 150) at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:83) at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:80) at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:80) and the table and foreign keys are not inserted. Also, especially weird: if I take the foreign key statements out of the script I showed above and then place them in their own script that executes after (so I now have 1 script with just the create table statement, and 1 script with the add foreign key statements that executes after that) then what happens is: tool executes create table script, works fine, table is created tool executes add fk script, throws the same exception as seen above (except errno=121 this time), but the FKs actually get added (!!!) In other words, when the create table/FK statements are in the same script then the exception is thrown and nothing is created, but when they are different scripts a nearly identical exception is thrown but both things get created. Any help on this would be greatly appreciated. Please let me know if you'd like me to clarify anything more.

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• How would you structure your entity model for storing arbitrary key/value data with different data t

  - by Nathan Ridley

  I keep coming across scenarios where it will be useful to store a set of arbitrary data in a table using a per-row key/value model, rather than a rigid column/field model. The problem is, I want to store the values with their correct data type rather than converting everything to a string. This means I have to choose either a single table with multiple nullable columns, one for each data type, or a set of value tables, one for each data type. I'm also unsure as to whether I should use full third normal form and separate the keys into a separate table, referencing them via a foreign key from the value table(s), or if it would be better to keep things simple and store the string keys in the value table(s) and accept the duplication of strings. Old/bad: This solution makes adding additional values a pain in a fluid environment because the table needs to be modified regularly. MyTable ============================ ID Key1 Key2 Key3 int int string date ---------------------------- 1 Value1 Value2 Value3 2 Value4 Value5 Value6 Single Table Solution This solution allows simplicity via a single table. The querying code still needs to check for nulls to determine which data type the field is storing. A check constraint is probably also required to ensure only one of the value fields contains non-nulll data. DataValues ============================================================= ID RecordID Key IntValue StringValue DateValue int int string int string date ------------------------------------------------------------- 1 1 Key1 Value1 NULL NULL 2 1 Key2 NULL Value2 NULL 3 1 Key3 NULL NULL Value3 4 2 Key1 Value4 NULL NULL 5 2 Key2 NULL Value5 NULL 6 2 Key3 NULL NULL Value6 Multiple-Table Solution This solution allows for more concise purposing of each table, though the code needs to know the data type in advance as it needs to query a different table for each data type. Indexing is probably simpler and more efficient because there are less columns that need indexing. IntegerValues =============================== ID RecordID Key Value int int string int ------------------------------- 1 1 Key1 Value1 2 2 Key1 Value4 StringValues =============================== ID RecordID Key Value int int string string ------------------------------- 1 1 Key2 Value2 2 2 Key2 Value5 DateValues =============================== ID RecordID Key Value int int string date ------------------------------- 1 1 Key3 Value3 2 2 Key3 Value6 How do you approach this problem? Which solution is better? Also, should the key column be separated into a separate table and referenced via a foreign key or be should it be kept in the value table and bulk updated if for some reason the key name changes?

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• Cocoa's newbie question: is it possible to bind a NSTableView's selection to another tableview's selection?

  - by cocoaOverloaded

  http://img651.imageshack.us/img651/6999/modelsf.jpg Let'say, I've 2 entities in the Core Data's Model file, one being all "transactions" ever done by X company. The "transactions" entity has among other properties, a "DATE" property and a to-one relationship "COMPANY"(specifying the company with which X company has done that particular transaction). The other entity:"companies" of course contains all the companies' info ,with which X company has done transaction. The "companies" entity has a to-many relationships "TRANSACTIONS" which is an inverse relationship to "transactions" entity's "COMPANY" relationship. So within IB, I created a NSTableView(with its own NSArrayController) showing all the transactions on a particular Date (with the help of NSPredicate). Then I create another table view showing the to-many relationship "TRANSACTIONS" of the company of the selected transaction in the first table view(which shows transactions on a particular date). The 2nd table view's NSArrayController binding is like this: ** bind to: "name of the first tableview's controller", Controller Key: selection, Model Key Path:COMPANY.TRANSACTIONS(the to-many relationship in the "companies" entity)** Everythings work fine up to this moment, the 2nd tableview shows all the transactions X company has done with the company of the selected transactions in the 1st table view. But I have a group of textfields showing details of a particular transactions. Binding the these textfields with the controller of the 1st table view(the one showing transactions on a particular date) is pretty straightforward. But what I want to do are: 1/ Look up the transactions on a particular date in the first table view, select any one of them 2/ Then, check all previous transactions of the company of that transaction( selected in the first table view) from the 2nd table view 3/ Select any previous transactions and check the details of the transaction from that group of textfields So naturally I should have bind the textfields' gp to the 2nd table view's controller. But I found the default selected row in the 2nd table view(the one show all previous transactions of a company) wasn't the transaction I've selected in the 1st tableView for a particular date. Of course, i can manually select that transaction in the 2nd table view again.... So I just want to know if it's possible to have the 2nd table view automatically select the transaction according to the transaction I've selected in the 1st table view thr binding?? After hours of googling, I solved the problem by implementing the tableview Delegate protocol: - (void)tableViewSelectionDidChange:(NSNotification *)aNotification { if (["nameOf1stTableView" selectedRow] > -1) { NSArray *objsArray = ["nameOf2ndTableView'sController" arrangedObjects]; for (id obj in objsArray) { if ([[obj valueForKey:@"DATE"] isEqualToDate: ["nameOf1stTableView'sController".selection valueForKey:@"DATE"]]) { ["nameOf2ndTableView" selectRowIndexes:[NSIndexSet indexSetWithIndex:[objsArray indexOfObject:obj]] byExtendingSelection:NO]; } } } } But,this just look too cumbersome... can it be done with binding alone? Thanks in Advance,

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• How to dismiss the table view created in the root view controller in iphone?

  - by Warrior

  I am new to iphone development. I have created a navigation based application. In the rootviewcontroller class i have written the code for parsing a url and display the contents in the table.In the didSelectRowAtIndexPath method i have written code for playing the video. NSURL *movieURL = [NSURL URLWithString:@"http://url of movie"]; if (movieURL) { if ([movieURL scheme]) { MovietryAppDelegate *appDelegate = (MovietryAppDelegate *)[[UIApplication sharedApplication] delegate]; [appDelegate initAndPlayMovie:movieURL]; } } In the delegate class i have defined the initAndPlayMovie method.I used the Apple sample "movie player " for my reference .I want to dismiss the table view before the video is loaded and table view appear back as presentmodalcontroller on clicking "done" button on video player.I want my app to work like you tube application. Please help me out.Thanks.

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• Silverlight RIA Services. Query fails on large table but works with Where clause

  - by FauxReal

  I have a somewhat large table, maybe 2000 rows by 50 columns. When using the most basic imaginable RIA implementation. Create one-table Model Create DomainService Drop datagrid onto MainPage.xaml Drop datasource onto datagrid Ctrl-F5 I get this error: System.ServiceModel.DomainServices.Client.DomainOperationException: Load operation faild for query. Value cannot be null. Error is much larger, but thats the beginning of it. The weird thing is that if I narrow the results down with a where clause on the GetQuery, it works fine. In fact six different querys which together result in all of the rows being called works fine also. So basically, I'm sure its not some sort of rogue row. Why do I get this "Value cannot be null" error if I query the whole table? Thanks

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• Assign table values to multiple variables using a single SELECT statement and CASE?

  - by Darth Continent

  I'm trying to assign values contained in a lookup table to multiple variables by using a single SELECT having multiple CASE statements. The table is a lookup table with two columns like so: [GreekAlphabetastic] SystemID Descriptor -------- ---------- 1 Alpha 2 Beta 3 Epsilon This is my syntax: SELECT @VariableTheFirst = CASE WHEN myField = 'Alpha' THEN tbl.SystemID END, @VariableTheSecond = CASE WHEN myField = 'Beta' THEN tbl.SystemID END, @VariableTheThird = CASE WHEN myField = 'Epsilon' THEN tbl.SystemID END FROM GreekAlphabetastic tbl However, when I check the variables after this statement executes, I expected each to be assigned the appropriate value, but instead only the last has a value assigned. SELECT @VariableTheFirst AS First, @VariableTheSecond AS Second, @VariableTheThird AS Third Results: First Second Third NULL NULL 3 What am I doing wrong?

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• How do I insert into a unique key into a table?

  - by Ben McCormack

  I want to insert data into a table where I don't know the next unique key that I need. I'm not sure how to format my INSERT query so that the value of the Key field is 1 greater than the maximum value for the key in the table. I know this is a hack, but I'm just running a quick test against a database and need to make sure I always send over a Unique key. Here's the SQL I have so far: INSERT INTO [CMS2000].[dbo].[aDataTypesTest] ([KeyFld] ,[Int1]) VALUES ((SELECT Max([KeyFld]) FROM [dbo].[aDataTypesTest]) + 1 ,1) which errors out with: Msg 1046, Level 15, State 1, Line 5 Subqueries are not allowed in this context. Only scalar expressions are allowed. I'm not able to modify the underlying database table. What do I need to do to ensure a unique insert in my INSERT SQL code?

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• Create new field in a table that already exists - flex/air sqlite?

  - by Adam

  I've got a flex/air app I've been working on, it uses a local sqlite database that is created on the initial application start. I've added some features to the application and in the process I had to add a new field to one of the database tables. My questions is how to I go about getting the application to create one new field that is located in a table that already exists? this is a the line that creates the table stmt.text = "CREATE TABLE IF NOT EXISTS tbl_status ("+"status_id INTEGER PRIMARY KEY AUTOINCREMENT,"+" status_status TEXT)"; And now I'd like to add a status_default field. thanks! Thanks - MPelletier I've add the code you provided and it does add the field, but now the next time I restart my app I get an error - 'status_default' already exists'. So how can I go about adding some sort of a IF NOT EXISTS statement to the line you provided?

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• Attempt to set foreign key to nonexistent table, sf_guard_user!

  - by Stick it to THE MAN

  I am using SF 1.3.2 with Propel ORM on Ubuntu 9.10. I created a new SF project and simply copied the sfGuard plugin folder from a pre-existing SF 1.32 project. I manually edited the schema.yml in the new project, adding a user table that reference the the sfGuard table. When I run propel:build-sql, I got the task failed, with the error message: Attempt to set foreign key to nonexistent table, sf_guard_user! I'm not sure why this error is occurring, (the error dosent make sense to me, since the sfGuard plugin works fine with the previous project, with no changes made. what am I missing?? BTW, I have not created any apps in the project yet. I am just running the build-sql task first, to make sure that Propel has no problems with parsing my yml files etc.

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• sql-server: how to select from dupilcate rows from table?

  - by RedsDevils

  Hi All, I have the following table. CREATE TABLE TEST(ID TINYINT NULL, COL1 CHAR(1)) INSERT INTO TEST(ID,COL1) VALUES (1,'A') INSERT INTO TEST(ID,COL1) VALUES (2,'B') INSERT INTO TEST(ID,COL1) VALUES (1,'A') INSERT INTO TEST(ID,COL1) VALUES (1,'B') INSERT INTO TEST(ID,COL1) VALUES (1,'B') INSERT INTO TEST(ID,COL1) VALUES (2,'B') I would like to select duplicate rows from that table. How Can I select? I try like the following: SELECT TEST.ID,TEST.COL1 FROM TEST WHERE TEST.ID IN (SELECT ID FROM TEST WHERE TEST.COL1 IN (SELECT COL1 FROM TEST WHERE TEST.ID IN (SELECT ID FROM TEST GROUP BY ID HAVING COUNT(*) > 1) GROUP BY COL1 HAVING COUNT(*) > 1) GROUP BY ID HAVING COUNT(*) > 1) Where's the Error? Can you modify that? Help me! Thanks in advance!

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• What are appropriate ways to represent relationships between people in a database table?

  - by Emilio

  I've got a table of people - an ID primary key and a name. In my application, people can have 0 or more real-world relationships with other people, so Jack might "work for" Jane and Tom might "replace" Tony and Bob might "be an employee of" Rob and Bob might also "be married to" Mary. What's the best way to represent this in the database? A many to many intersect table? A series of self joins? A relationship table with one row per relationship pair and type, where I insert records for the relationship in both directions?

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• Rails: Polymorphic User Table a good idea with AuthLogic?

  - by sscirrus

  Hi everyone, I have a system where I need to login three user types: customers, companies, and vendors from one login form on the home page. I have created one User table that works according to AuthLogic's example app at http://github.com/binarylogic/authlogic_example. I have added a field called "User Type" that currently contains either 'Customer', 'Company', or 'Vendor'. Note: each user type contains many disparate fields so I'm not sure if Single Table Inheritance is the best way to go (would welcome corrections if this conclusion is invalid). Is this a polymorphic association where each of the three types is 'tagged' with a User record? How should my models look so I have the right relationships between my User table and my user types Customer, Company, Vendor? Thanks very much!

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• How do you handle descriptive database table names and their effect on foreign key names?

  - by Carvell Fenton

  Hello, I am working on a database schema, and am trying to make some decisions about table names. I like at least somewhat descriptive names, but then when I use suggested foreign key naming conventions, the result seems to get ridiculous. Consider this example: Suppose I have table session_subject_mark_item_info And it has a foreign key that references sessionSubjectID in the session_subjects table. Now when I create the foreign key name based on fk_[referencing_table]__[referenced_table]_[field_name] I end up with this maddness: fk_session_subject_mark_item_info__session_subjects_sessionSubjectID Would this type of a foreign key name cause me problems down the road, or is it quite common to see this? Also, how do the more experienced database designers out there handle the conflict between descriptive naming for readability vs. the long names that result? I am using MySQL and MySQL Workbench if that makes any difference. Thanks!

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• SQL query: Delete a entry which is not present in a join table?

  - by Mestika

  Hi, I’m going to delete all users which has no subscription but I seem to run into problems each time I try to detect the users. My schemas look like this: Users = {userid, name} Subscriptionoffering = {userid, subscriptionname} Now, what I’m going to do is to delete all users in the user table there has a count of zero in the subscriptionoffering table. Or said in other words: All users which userid is not present in the subscriptionoffering table. I’ve tried with different queries but with no result. I’ve tried to say where user.userid <> subscriptionoffering.userid, but that doesn’t seem to work. Do anyone know how to create the correct query? Thanks Mestika

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• How to add a column via a query which counts the total rows with a specific criteria in a table with circular relationship in MS ACCESS 2007

  - by Xaqron

  I have a simple table "Employees" with this fields: ID, ParentID, Name ParentID is Nullable since an employee may have no Manager. This table has a one-to-many relationship with itself: ID --one--to--many--> ParentID Now I want a query which returns this columns: Name, Count of rows where their ParentID equals to the current row ID (the row is the manager of that rows) Sample Table: ID | ParentID | Name ====================== 1 | 0 | John ---------------------- 2 | 1 | Bob ---------------------- 3 | 1 | Alice ---------------------- 4 | 3 | Jack This way I can find an employee is the manager of how many other employees. The result should be something like this: Name | Count of Employees ========================== John | 2 -------------- Bob | 0 -------------- Alice | 1 -------------- Jack | 0 How can I achieve this in MS ACCESS 2007? * I have tried built-in query builder without any success.

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• In Rails: How can I turn off caching for a particular activerecord database table?

  - by pmneve

  I have an associative table (scripts_runs) (has_many, through) that carries a status column ('started', 'ready to parse', 'completed' ). The started and ready to parse states are signaled by 'flag' files from distributed executions of the scripts pickedup periodically (20 seconds). The completed status is written directly to the associative table by the parser when it is done. With short scripts the complete status is written before the ready to parse flag file is picked up. Because the row from the table is cached, the complete status is not seen by the observer for the flag files and gets overwritten by the ready to parse status. This is not good. I need the status to be updated in the database in the correct sequence so an Ajax periodic query can inform the user of the status of each script and when the run ( consisting of one to many scripts ) is completed. Can I force the ScriptRun.find(:id) to always go to the database? If so how? If not, why not???

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• Databases design - one link table or multiple link tables?

  - by David

  Hi there, I'm working on a front end for a database where each table essentially has a many to many relationship with all other tables. I'm not a DB admin, just a few basic DB courses. The typical solution in this case, as I understand it, would be multiple link tables to join each 'real' table. Here's what I'm proposing instead: one link table that has foreign key dependencies to all other PKs of the other tables. Is there any reason this could turn out badly in terms of scalability, flexibility, etc down the road?

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