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  • (NOT) NULL for NVARCHAR columns

    - by Anders Abel
    Allowing NULL values on a column is normally done to allow the absense of a value to be represented. When using NVARCHAR there is aldready a possibility to have an empty string, without setting the column to NULL. In most cases I cannot see a semantical difference between an NVARCHAR with an empty string and a NULL value for such a column. Setting the column as NOT NULL saves me from having to deal with the possibility of NULL values in the code and it feels better to not have to different representations of "no value" (NULL or an empty string). Will I run into any other problems by setting my NVARCHAR columns to NOT NULL. Performance? Storage size? Anything I've overlooked on the usage of the values in the client code?

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  • Caching stored procedure results in Linq'u

    - by itdebeloper
    In our web application we have a lots of stored procedures look like this one: getSomeData(/* 7 diffrent params */) This stored procedure don't make any updates. We are using Linq'u. I know that the date are changing no often than once per day so the results for the same sets of parameters values will be the same. Does Linqu have cache simple solution? I know how to 'manually' write cache mechanism in .net, but I supposed that in Linqu this problem was solved. I'm a lazy guy :) so I'm looking for something realy simple like: Linqu_global_store_procedure_configuration.CacheDuration="600" Linqu_global_store_procedure_configuration.CacheVaryByParam="*" I'm using .net 3.5 but its not any problem to move for 4.0.

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  • Password security; Is this safe?

    - by Camran
    I asked a question yesterday about password safety... I am new at security... I am using a mysql db, and need to store users passwords there. I have been told in answers that hashing and THEN saving the HASHED value of the password is the correct way of doing this. So basically I want to verify with you guys this is correct now. It is a classifieds website, and for each classified the user puts, he has to enter a password so that he/she can remove the classified using that password later on (when product is sold for example). In a file called "put_ad.php" I use the $_POST method to fetch the pass from a form. Then I hash it and put it into a mysql table. Then whenever the users wants to delete the ad, I check the entered password by hashing it and comparing the hashed value of the entered passw against the hashed value in the mysql db, right? BUT, what if I as an admin want to delete a classified, is there a method to "Unhash" the password easily? sha1 is used currently btw. some code is very much appreciated. Thanks

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  • insert a time-stamp value in my db by php

    - by Erick
    I'm using oracle express and in my application i would insert a time-stamp value in my table: $marca = date('y-m-d H:i:s'); $query = " INSERT INTO SA_VERSIONE ( ID_ACCETTAZIONE, MARCA_TEMPORALE, TESTO, FIRMA, MEDICO) VALUES ('$id', '$marca', '$testo', '$firma', '$medico') "; $stid = oci_parse($conn, $query); oci_execute($stid); but when execute it return: Warning: oci_execute() [function.oci-execute]: ORA-01843: mese non valido in ... and say that the month is not valid

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  • Storing object into cache using Linq classes and velocity

    - by Arun
    I careated couple of linq classes & marked the datacontext as unidirectional. Out of four classes; one is main class while other three are having the one to many relationship with first one; When I load the object of main class & put into the memory OR serialize it into an XML file; I never get the child class data while it is maked as DataContractAttribute. How can I force object to put the child class data into XML file or into cache ?

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  • What is the reason not to use select * ?

    - by Chris Lively
    I've seen a number of people claim that you should specifically name each column you want in your select query. Assuming I'm going to use all of the columns anyway, why would I not use SELECT *? Even considering the question from 9/24, I don't think this is an exact duplicate as I'm approaching the issue from a slightly different perspective. One of our principles is to not optimize before it's time. With that in mind, it seems like using SELECT * should be the preferred method until it is proven to be a resource issue or the schema is pretty much set in stone. Which, as we know, won't occur until development is completely done. That said, is there an overriding issue to not use SELECT *?

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  • How do I make my MySQL query with joins more concise?

    - by John Hoffman
    I have a huge MySQL query that depends on JOINs. SELECT m.id, l.name as location, CONCAT(u.firstName, " ", u.lastName) AS matchee, u.email AS mEmail, u.description AS description, m.time AS meetingTime FROM matches AS m LEFT JOIN locations AS l ON locationID=l.id LEFT JOIN users AS u ON (u.id=m.user1ID) WHERE m.user2ID=2 UNION SELECT m.id, l.name as location, CONCAT(u.firstName, " ", u.lastName) AS matchee, u.email AS mEmail, u.description AS description, m.time AS meetingTime FROM matches AS m LEFT JOIN locations AS l ON locationID=l.id LEFT JOIN users AS u ON (u.id=m.user2ID) WHERE m.user1ID=2 The first 3 lines of each sub-statement divided by UNION are identical. How can I abide by the DRY principle, not repeat those three lines, and make this query more concise?

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  • How to merge existing row with new data in SQLite?

    - by CSharperWithJava
    I have a database full of simple note data, with columns for title, due date, priority, and details. There is also a _id column PRIMARY KEY int. Say I have a note in the table already with some data filled and the rest null. I also have a set of data that will fill all those fields. Is there a way that I can only write data to the fields that are NULL? I can't overwrite existing data, but I'd like to add data to NULL columns. I know the rowId of the target row. If my target row had rowId of 5, I could do something like this: UPDATE SET duedate='some date', priority='2', details='some text' WHERE _id=5 But that would overwrite all the data in that row, and I don't want to lose any data that might be there. How can I change this statement to avoid writing to non-null fields?

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  • How would I implement separate databases for reading and writing operations?

    - by Matt
    I am interested in implementing an architecture that has two databases one for read operations and the other for writes. I have never implemented something like this and have always built single database, highly normalised systems so I am not quite sure where to begin. I have a few parts to this question. 1. What would be a good resource to find out more about this achitecture? 2. Is it just a question of replicating between two identical schemas, or would your schemas differ depending on the operations, would normalisation vary too? 3. How do you insure that data written to one database is immediately available for reading from the second? Any further help, tips, resources would be appreciated. Thanks.

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  • How to create a better tables Structure.

    - by user160820
    For my website i have tables Category :: id | name Product :: id | name | categoryid Now each category may have different sizes, for that I have also created a table Size :: id | name | categoryid | price Now the problem is that each category has also different ingredients that customer can choose to add to his purchased product. And these ingredients have different prices for different sizes. For that I also have a table like Ingredient :: id | name | sizeid | categoryid | price I am not sure if this Structure really normalized is. Can someone please help me to optimize this structure and which indexed do i need for this Structure?

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  • SQL time issue - need it 6 hours forward!

    - by Luke
    My server is currently based on us eastern time, and as I am in the UK, i need to move this forward 6 hours. When using now() in mysql, i am getting the wrong time, is there anything i can add to now() to bring it forward 6 hours? Thanks

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  • What is this hacker trying to do?

    - by JW
    If you do a search for: http://www.google.co.uk/search?q=0x57414954464F522044454C4159202730303A30303A313527&hl=en&start=30&sa=N you will see a lot of examples of an attempted hack along the lines of: 1) declare @q varchar(8000) select @q = 0x57414954464F522044454C4159202730303A30303A313527 exec(@q) -- What is exactly is it trying to do? Which db is it trying to work on? Do you know of any advisories about this?

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  • Alter multiple tables' columns length

    - by gdoron
    So, we just found out that 254 tables in our Oracle DBMS have one column named "Foo" with the wrong length- Number(10) instead of Number(3). That foo column is a part from the PK of the tables. Those tables have other tables with forigen keys to it. What I did is: backed-up the table with a temp table. Disabled the forigen keys to the table. Disabled the PK with the foo column. Nulled the foo column for all the rows. Restored all the above But now we found out it's not just couple of tables but 254 tables. Is there an easy way, (or at least easier than this) to alter the columns length? P.S. I have DBA permissions.

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  • add array element to row returned from sql query

    - by bert
    I want to add an additional value into an array before passing it to json_encode function, but I can't get the syntax right. $result = db_query($query); // $row is a database query result resource while ($row = db_fetch_object($result)) { $stack[] = $row; // I am trying to 'inject' array element here $stack[]['x'] = "test"; } echo json_encode($stack);

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  • Losing scope for DataContex using LINQToSQL intermediately

    - by greektreat
    I am having a weird Situation with my DataConext. All My code is in C# I have a DLL project for my data access layer and business Layer which and Winforms project for my UI layer. My Data access Layer's Namespace is xxx.Data this is where have my xxx.dbml I also have xxx.Data.BusinessObjects name space of course for my business object in that project In my UI Layer I have these namespaces xxxApp(for Forms), xxxApp.Controls (For Controls) I have lost scope of the DataContext, it was accessible now when I do a Rebuild Solution I sometimes get compile errors saying for example: Error 34 'xxx.Data.xxxDataContext' does not contain a definition for 'SubmitChanges' and no extension method 'SubmitChanges' accepting a first argument of type 'xxx.Data.xxxDataContext' could be found (are you missing a using directive or an assembly reference?) Also intelisense doesn't recognize the methods and table classes from my xxxDataContext anymore I can access all object fine when I am in the DLL project but now in the Winforms project this is very strange. If anyone can help me out I would be extremely grateful!

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  • Beginner Ques::How to delete records permanently in case of linked tables?

    - by Serenity
    Let's say I have these 2 tables QuesType and Ques:- QuesType QuestypeID|QuesType |Active ------------------------------------ 101 |QuesType1 |True 102 |QuesType2 |True 103 |XXInActiveXX |False Ques QuesID|Ques|Answer|QUesTypeID|Active ------------------------------------ 1 |Ques1|Ans1 |101 |True 2 |Ques2|Ans2 |102 |True 3 |Ques3|Ans3 |101 |True In the QuesType Table:- QuesTypeID is a Primary key In the Ques Table:- QuesID is a Primary key and QuesType ID is the Foreign Key that refernces QuesTypeID from QuesType Table Now I am unable to delete records from QuesType Table, I can only make QuesType inactive by setting Active=False. I am unable to delete QuesTypes permanently because of the Foreign key relation it has with Ques Table. So , I just set the column Active=false and those Questypes then don't show on my grid wen its binded. What I want to do is be able to delete any QuesType permamnently. Now it can only be deleted if its not being used anywhere in the Ques table, right? So to delete any QuesType permanently I thot this is what I could do:- In the grid that displays QuesTypes, I have this check box for Active and a button for delete.What I thot was, when a user makes some QuesType inactive then OnCheckChanged() event will run and that will have the code to delete all the Questions in Ques table that are using that QuesTypeID. Then on the QuesType grid, that QuesType would show as Deactivated and only then can a user delete it permanently. Am I thinking correctly? Currently in my DeleteQuesType Stored Procedure what I am doing is:- Setting the Active=false and Setting QuesTye= some string like XXInactiveXX Is there any other way?

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  • MySQL- complex data query in a single statement

    - by yoda
    Hi, Consider the following structure : Ignore the table user_token. Now, imagine that you need to get all the roles related to an user, wich may be through it's related groups or directly related to him. In case the same role appears related to a group and the user directly, the role related to the user will prevail over the role given by the group. Is there any chance this could be done in a single query? Cheers!

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  • What should I use to increase performance. View/Query/Temporary Table

    - by Shantanu Gupta
    I want to know the performance of using Views, Temp Tables and Direct Queries Usage in a Stored Procedure. I have a table that gets created every time when a trigger gets fired. I know this trigger will be fired very rare and only once at the time of setup. Now I have to use that created table from triggers at many places for fetching data and I confirms it that no one make any changes in that table. i.e ReadOnly Table. I have to use this tables data along with multiple tables to join and fetch result for further queries say select * from triggertable By Using temp table select ... into #tx from triggertable join t2 join t3 and so on select a,b, c from #tx --do something select d,e,f from #tx ---do somethign --and so on --around 6-7 queries in a row in a stored procedure. By Using Views create view viewname ( select ... from triggertable join t2 join t3 and so on ) select a,b, c from viewname --do something select d,e,f from viewname ---do somethign --and so on --around 6-7 queries in a row in a stored procedure. This View can be used in other places as well. So I will be creating at database rather than at sp By Using Direct Query select a,b, c from select ... into #tx from triggertable join t2 join t3 join ... --do something select a,b, c from select ... into #tx from triggertable join t2 join t3 join ... --do something . . --and so on --around 6-7 queries in a row in a stored procedure. Now I can create a view/temporary table/ directly query usage in all upcoming queries. What would be the best to use in this case.

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  • Mysql query help needed

    - by Me-and-Coding
    Hi, i have two tables category and hotels where category.id should be equal to hotels.catid. Now how do i select 3 rows from each different category from the hotels table. I have this query: select h.* from hotels h inner join category c on h.catid = c.id order by h.catid, h.hid this selects all records, but i want to select three rows per different category so in all it should return 9 rows with 3 rows for each category. If this can not be done in mysql, you could also suggest php code please. Thanks

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