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  • What is the difference between check and foreign key?

    - by GigaPr
    Hi, i am quite confused about the difference between a FOREIGN KEY and CHECK constraint. they appear to me to achieve the same result. I mean I could create a table and enforce a Foreign key on another table, but i could create a CHECK to ensure the value in in another table. What is the difference and when to use the one or the other? thanks

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  • LINQ - 'Could not translate expression' with previously used and proven query condition

    - by tomfumb
    I am fairly new to LINQ and can't get my head around some inconsistency in behaviour. Any knowledgeable input would be much appreciated. I see similar issues on SO and elsewhere but they don't seem to help. I have a very simple setup - a company table and an addresses table. Each company can have 0 or more addresses, and if 0 one must be specified as the main address. I'm trying to handle the cases where there are 0 addresses, using an outer join and altering the select statement accordingly. Please note I'm currently binding the output straight to a GridView so I would like to keep all processing within the query. The following DOES work IQueryable query = from comp in context.Companies join addr in context.Addresses on comp.CompanyID equals addr.CompanyID into outer // outer join companies to addresses table to include companies with no address from addr in outer.DefaultIfEmpty() where (addr.IsMain == null ? true : addr.IsMain) == true // if a company has no address ensure it is not ruled out by the IsMain condition - default to true if null select new { comp.CompanyID, comp.Name, AddressID = (addr.AddressID == null ? -1 : addr.AddressID), // use -1 to represent a company that has no addresses MainAddress = String.Format("{0}, {1}, {2} {3} ({4})", addr.Address1, addr.City, addr.Region, addr.PostalCode, addr.Country) }; but this displays an empty address in the GridView as ", , ()" So I updated the MainAddress field to be MainAddress = (addr.AddressID == null ? "" : String.Format("{0}, {1}, {2} {3} ({4})", addr.Address1, addr.City, addr.Region, addr.PostalCode, addr.Country)) and now I'm getting the Could not translate expression error and a bunch of spewey auto-generated code in the error which means very little to me. The condition I added to MainAddress is no different to the working condition on AddressID, so can anybody tell me what's going on here? Any help greatly appreciated.

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  • MySQL, select from different table... IF

    - by gubbfett
    I'm having a small trouble since it was a long time ago i studies databases and querys. For example i'll have two tables for cd:s, one with data and one with alternative translations. In the CD-table i have the original language, and it looks something like this Table for CDs (cds): id | name | language ----------------------- 1 | aaa | en 2 | bbb | en 3 | ccc | fi Table for languages (languages): cd_id | language | name ----------------------- 1 | fi | AAA 1 | de | AAACHTUNG 3 | en | CCC Now, i want to get all these cd:s in for example german, if there's no translation made i want it to be in the original language... How can i do this?

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  • MySQL Delete Records Older Than X Minutes?

    - by sajanNOPPIX
    I've searched quite a bit and found a few solutions that didn't end up working for me and can't understand why. I have a table with a timestamp column. The MySQL type for this column is 'datetime'. I insert into this table the following from PHP. date('Y-m-d H:i:s') This enters, what looks like the correct value for the MySQL date time. 2012-06-28 15:31:46 I want to use this column to delete rows that are older than say 10 minutes. I'm running the following query, but it's not working. It affects 0 rows. DELETE FROM adminLoginLog WHERE timestamp < (NOW() - INTERVAL 10 MINUTE); Can anyone shed some light as to what I'm doing wrong and why it's not working properly? Thanks. Update: It looks like my first issue is that I'm using DATETIME when I should be using the TIMESTAMP data type. I'm updating my code to do that now. Thanks.

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  • Mysql query problem

    - by Lost_in_code
    Below is a sample table: fruits +-------+---------+ | id | type | +-------+---------+ | 1 | apple | | 2 | orange | | 3 | banana | | 4 | apple | | 5 | apple | | 6 | apple | | 7 | orange | | 8 | apple | | 9 | apple | | 10 | banana | +-------+---------+ Following are the two queries of interest: SELECT * FROM fruits WHERE type='apple' LIMIT 2; SELECT COUNT(*) AS total FROM fruits WHERE type='apple'; // output 6 I want to combine these two queries so that the results looks like this: +-------+---------+---------+ | id | type | total | +-------+---------+---------+ | 1 | apple | 6 | | 4 | apple | 6 | +-------+---------+---------+ The output has to be limited to 2 records but it should also contain the total number of records of the type apple. How can this be done with 1 query?

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  • Linqbuilder Query with an OrderBy

    - by Renshai
    I have a 1 : M relationship. I built a dynamic query based on input from users to return the listing of parents entities along with their children (using predicate builder: (done successfully new TDataContext().Ps.Where(predicate) )... but need to order the results by a field found only on the child entities. I'm at a loss: new TDataContext().Ps.Where(predicate).OrderBy(p = p.Cs. ??) where Ps = parents collection relationship with Cs = child entities any help appreciated.

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  • How can I find all records for a model without doing a long list of "OR" conditions?

    - by gomezuk
    I'm having trouble composing a CakePHP find() which returns the records I'm looking for. My associations go like this: User -(has many)- Friends , User -(has many)- Posts I'm trying to display a list of all a user's friends recent posts, in other words, list every post that was created by a friend of the current user logged in. The only way I can think of doing this is by putting all the user's friends' user_ids in a big array, and then looping through each one, so that the find() call would look something like: $posts = $this->Post->find('all',array( 'conditions' => array( 'Post.user_id' => array( 'OR' => array( $user_id_array[0],$user_id_array[1],$user_id_array[2] # .. etc ) ) ) )); I get the impression this isn't the best way of doing things as if that user is popular that's a lot of OR conditions. Can anyone suggest a better alternative?

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  • check if sqlserver is installed on a machine thro C#

    - by Skun
    Hey ! I am making an application which is a user interface to access 2 types of databases - SQLite and MSSQL server. The thing is, SQLite doesnt need to be "installed" since its just a flatfile database, but on the other hand, SQLserver (Express/normal) need to be installed before use. My Question is simple: Is there a way by which i can find out if an instance of SQLserver has been installed on the local machine by using a C# program?

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  • Help with query in Microsoft Access

    - by Gold
    I have 2 tables: Table A: code | name Table B: barcode | name Table B has full barcode and name, Table A has only code. I need to run update query that fill name in Table A. I tried something like: update A set name = (select top 1 Name from B where B.Code = mid(A.Barcode,1,8)) but it doesn't work.

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  • Sorting nested set by name while keep depth integrity

    - by wb
    I'm using the nested set model that'll later be used to build a sitemap for my web site. This is my table structure. create table departments ( id int identity(0, 1) primary key , lft int , rgt int , name nvarchar(60) ); insert into departments (lft, rgt, name) values (1, 10, 'departments'); insert into departments (lft, rgt, name) values (2, 3, 'd'); insert into departments (lft, rgt, name) values (4, 9, 'a'); insert into departments (lft, rgt, name) values (5, 6, 'b'); insert into departments (lft, rgt, name) values (7, 8, 'c'); How can I sort by depth as well as name? I can do select replicate('----', count(parent.name) - 1) + ' ' + node.name , count(parent.name) - 1 as depth , node.lft from departments node , departments parent where node.lft between parent.lft and parent.rgt group by node.name, node.lft order by depth asc, node.name asc; However, that does not match children with their parent for some reason. department lft rgt --------------------------- departments 0 1 ---- a 1 4 ---- d 1 2 -------- b 2 5 -------- c 2 7 As you can see, department 'd' has department 'a's children! Thank you.

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  • excel quotes in formula question

    - by I__
    i have a column with this data: IT_AMPH IT_BARB IT_BENZ IT_BUP SOMA i want the column next to it to be literarely =like "*,IT_AMPH,*" =like "*,IT_BARB,*" =like "*,IT_BENZ,*" etc please note that i want the equal signed to be displayed, exactly as shown above what would be the formula for this?

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  • replicating master tables mapping in transaction tables

    - by NoDisplay
    I have three master tables for location information Country {ID, Name} State {ID, Name, CountryID} City {ID, Name, StateID} Now I have one transcation table called Person which hold the person name and his location information. My Question is shall I have only CityID in the Person table like this: Person {ID, Name, CityID}' And have view of join query which give me detail like "Person{ID,Name,City,State,Country}" or Shall I replicate the mapping Person {ID, Name, CityID, StateID, CountryID} Please suggest which do you feel is to be selected and why? if there is any other option available, please suggest. Thanks in advance.

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  • self join table

    - by San82moon
    HI, i have a table, new_id----old_id----created_on 1234------5678------20100912 5678------3456------20100808 etc. i wrote this query, $q = "select event1.new_id, event1.old_id, event1.created_on,event2.new_id, event2.old_id, event2.created_on FROM replaced_isbns event1 JOIN replaced_isbns event2 ON event2.new_id = event1.old_id WHERE event1.new_id='$id'"; but i get result as 5678 - 1234, ie only one row, i want all rows... plz help me. Thanks, SLC

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  • Improving performance for WRITE operation on Oracle DB in Java

    - by Lucky
    I've a typical scenario & need to understand best possible way to handle this, so here it goes - I'm developing a solution that will retrieve data from a remote SOAP based web service & will then push this data to an Oracle database on network. Also, this will be a scheduled task that will execute every 15 minutes. I've event queues on remote service that contains the INSERT/UPDATE/DELETE operations that have been done since last retrieval, & once I retrieve the events for last 15 minutes, it again add events for next retrieval. Now, its just pushing data to Oracle so all my interactions are INSERT & UPDATE statements. There are around 60 tables on Oracle with some of them having 100+ columns. Moreover, for every 15 minutes cycle there would be around 60-70 Inserts, 100+ Updates & 10-20 Deletes. This will be an executable jar file that will terminate after operation & will again start on next 15 minutes cycle. So, I need to understand how should I handle WRITE operations (best practices) to improve performance for this application as whole ? Current Test Code (on every cycle) - Connects to remote service to get events. Creates a connection with DB (single connection object). Identifies the type of operation (INSERT/UPDATE/DELETE) & table on which it is done. After above, calls the respective method based on type of operation & table. Uses Preparedstatement with positional parameters, & retrieves each column value from remote service & assigns that to statement parameters. Commits the statement & returns to get event class to process next event. Above is repeated till all the retrieved events are processed after which program closes & then starts on next cycle & everything repeats again. Thanks for help !

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  • Cursor loops; How to perform something at start/end of loop 1 time only?

    - by James.Elsey
    I've got the following in one of my Oracle procedures, I'm using it to generate XML -- v_client_addons is set to '' to avoid null error OPEN C_CLIENT_ADDONS; LOOP FETCH C_CLIENT_ADDONS INTO CLIENT_ADDONS; EXIT WHEN C_CLIENT_ADDONS%NOTFOUND; BEGIN v_client_addons := v_client_addons || CLIENT_ADDONS.XML_DATA; END; END LOOP; CLOSE C_CLIENT_ADDONS; -- Do something later with v_client_addons The loop should go through my cursor and pick out all of the XML values to display, such as : <add-on name="some addon"/> <add-on name="another addon"/> What I would like to achieve is to have an XML start/end tag inside this loop, so I would have the following output <addons> <add-on name="some addon"/> <add-on name="another addon"/> </addons> How can I do this without having the <addons> tag after every line? If there are no addons in the cursor (cursor is empty), then I would like to skip this part enitrely

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  • Updating counters through Hibernate

    - by at
    This is an extremely common situation, so I'm expecting a good solution. Basically we need to update counters in our tables. As an example a web page visit: Web_Page -------- Id Url Visit_Count So in hibernate, we might have this code: webPage.setVisitCount(webPage.getVisitCount()+1); The problem there is reads in mysql by default don't pay attention to transactions. So a highly trafficked webpage will have inaccurate counts. The way I'm used to doing this type of thing is simply call: update Web_Page set Visit_Count=Visit_Count+1 where Id=12345; I guess my question is, how do I do that in Hibernate? And secondly, how can I do an update like this in Hibernate which is a bit more complex? update Web_Page wp set wp.Visit_Count=(select stats.Visits from Statistics stats where stats.Web_Page_Id=wp.Id) + 1 where Id=12345;

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  • How to completely remove MySQL from a windows 7 machine

    - by Jazibobs
    I'm new to MySQL struggling to find a version and workbench which works stably on my 64 bit windows 7 machine. I've decided to attempt to completely remove MySQL from my machine and to restart the installation process from scratch. However, after uninstalling all software linked with MySQL using conventional control panel uninstalling means some MySQL windows services still remain on my machine. I can't see any obvious method to remove these and they have since been causing me difficulties when trying to install different versions of MySQL. Could anyone please advise?

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