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• Clustered index on frequently changing reference table of one or more foreign keys

  - by Ian

  My specific concern is related to the performance of a clustered index on a reference table that has many rapid inserts and deletes. Table 1 "Collection" collection_pk int (among other fields) Table 2 "Item" item_pk int (among other fields) Reference Table "Collection_Items" collection_pk int, item_pk int (combined primary key) Because the primary key is composed of both pks, a clustered index is created and the data physically ordered in the table according to the combined keys. I have many users creating and deleting collections and adding and removing items to those collections very frequently affecting the "Collection_Items" table, and its clustered index. QUESTION PART: Since the "Collection_Items" table is so dynamic, wouldn't there be a big performance hit on constantly resorting the table rows because of the clustered index ? If yes, what should I do to minimize this ?

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• Database design advice needed.

  - by user346271

  Hi all, I'm a lone developer for a telecoms company, and am after some database design advice from anyone with a bit of time to answer. I am inserting into one table ~2 million rows each day, these tables then get archived and compressed on a monthly basis. Each monthly table contains ~15,000,000 rows. Although this is increasing month on month. For every insert I do above I am combining the data from rows which belong together and creating another "correlated" table. This table is currently not being archived, as I need to make sure I never miss an update to the correlated table. (Hope that makes sense) Although in general this information should remain fairly static after a couple of days of processing. All of the above is working perfectly. However my company now wishes to perform some stats against this data, and these tables are getting too large to provide the results in what would be deemed a reasonable time. Even with the appropriate indexes set. So I guess after all the above my question is quite simple. Should I write a script which groups the data from my correlated table into smaller tables. Or should I store the queries result sets in something like memcache? I'm already using mysqls cache, but due to having limited control over how long the data is stored for, it's not working ideally. The main advantages I can see of using something like memcache: No blocking on my correlated table after the query has been cashed. Greater flexibility of sharing the collected data between the backend collector and front end processor. (i.e custom reports could be written in the backend and the results of these stored in the cache under a key which then gets shared with anyone who would want to see the data of this report) Redundancy and scalability if we start sharing this data with a large amount of customers. The main disadvantages I can see of using something like memcache: Data is not persistent if machine is rebooted / cache is flushed. The main advantages of using MySql Persistent data. Less code changes (although adding something like memcache is trivial anyway) The main disadvantages of using MySql Have to define table templates every time I want to store provide a new set of grouped data. Have to write a program which loops through the correlated data and fills these new tables. Potentially will still grow slower as the data continues to be filled. Apologies for quite a long question. It's helped me to write down these thoughts here anyway, and any advice/help/experience with dealing with this sort of problem would be greatly appreciated. Many thanks. Alan

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• MySQL whats wrong with my foreign keys?

  - by Skiy

  Hello, what is wrong with the two foreign keys which I have marked with comments? create database db; use db; create table Flug( Flugbez varchar(20), FDatum Date, Ziel varchar(20), Flugzeit int, Entfernung int, Primary Key (Flugbez, FDatum)); create table Flugzeugtyp( Typ varchar(20), Hersteller varchar(20), SitzAnzahl int, Reisegeschw int, primary key (Typ) ); create table flugzeug( Typ varchar(20), SerienNr int, AnschDatum Date, FlugStd int, primary key(Typ,SerienNr), foreign key(Typ) references Flugzeugtyp(Typ)); create table Abflug( Flugbez varchar(20), FDatum Date, Typ varchar(20), Seriennr int, Kaptaen varchar(20), Primary key(Flugbez,FDatum,Typ,SerienNr), Foreign key(Flugbez) references Flug(Flugbez), -- Foreign key(FDatum) references Flug(FDatum), Foreign key(Typ) references Flugzeugtyp(Typ) -- ,Foreign key(SerienNr) references Flugzeug(SerienNr) ); When I uncomment these, I get: ERROR 1005 (HY000): Can't create table 'db.abflug' (errno: 150)

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• Why might one app connect to SQL backend OK and a second app fail if they share the same connectionstring?

  - by hawbsl

  Trying to figure out a SQL connection error 26 in our app. We've got two closely related apps Foo and FooAddIn. Foo is a Winforms app built in VS2010 and runs fine and connects fine to our SQLExpress back end. FooAddIn is an Outlook AddIn which references Foo.exe and connects to the same SQL Express instance. Or rather, it doesn't connect, instead reporting: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) Now, both apps share the same connectionstring and we've verified they really do share the same connectionstring. At this stage we're just testing from within the same developer machine, so the apps are on the same machine, going via the same VS2010 IDE. So a lot of the advice online for this error doesn't apply because the fact that Foo connects through to SQL Express tells us the database is there and available and can be reached. What else is there to check? One thing is that Foo and FooAddIn are running different runtime versions of System.Data (v2.0.50727 and v4.0.30319). Could that be a factor?

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• Dynamic where clause in LINQ - with column names available at runtime

  - by sandesh247

  Disclaimer: I've solved the problem using Expressions from System.Linq.Expressions, but I'm still looking for a better/easier way. Consider the following situation : var query = from c in db.Customers where (c.ContactFirstName.Contains("BlackListed") || c.ContactLastName.Contains("BlackListed") || c.Address.Contains("BlackListed")) select c; The columns/attributes that need to be checked against the blacklisted term are only available to me at runtime. How do I generate this dynamic where clause? An additional complication is that the Queryable collection (db.Customers above) is typed to a Queryable of the base class of 'Customer' (say 'Person'), and therefore writing c.Address as above is not an option.

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• Calendar using Javascript/ PHP/ mySQL

  - by Gushiken

  for a current webapp i need a "outlook-like" calendar... Here are some requirements for the calendar: week-view for the appointments different appointment types direct display of the length and time of the date (like in googleCalendar) multiple appointments for the same time only using javascript, php and any DB We need the calendar for the Zend Framework, so if the Calendar doesn't already support the ZF, the source needs to be editable! do you know any calendar which fits my needs? or do you have any tipps for developing one by myself?

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• How to store data with N columns

  - by iconiK

  I need a way to store an int for N columns. Basically what I have is this: Armies: ArmyID - UINT UnitCount1 - UINT UnitCount2 - UINT UnitCount3 - UINT UnitCount4 - UINT ... I can't possible add a column for each and every unit, so I need a fast way to store the number of each units in an army (you might have guesses it's for a game by now). Using XML is not an option as it will be dead slow.

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• Select count() max() Date HELP!!! mysql oracle

  - by DAVID

  Hi guys i have a table with shifts history along with emp ids im using this code to retrieve a list of employees and their total shifts by specifying the range to count from: SELECT ope_id, count(ope_id) FROM operator_shift WHERE ope_shift_date >=to_date( '01-MAR-10','dd-mon-yy') and ope_shift_date <= to_date('31-MAR-10','dd-mon-yy') GROUP BY OPE_ID which gives OPE_ID COUNT(OPE_ID) 1 14 2 7 3 6 4 6 5 2 6 5 7 2 8 1 9 2 10 4 10 rows selected. NOW how do i choose the employee with the highest no of shifts under the specified range date, please this is really important

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• Entity Framework EntityKey / Foreign Key problem.

  - by Ronny176

  Hi, I keep getting the same error: Entities in 'VlaamseOverheidMeterEntities.ObjectMeter' participate in the 'FK_ObjectMeter_Meter' relationship. 0 related 'Meter' were found. 1 'Meter' is expected. I have the following table structure: Meter 1 <- * ObjectMeter * - 1 VO_Object It is always the same scenario: The first meter is added to the database, the second meter gives the error above. I have the following code in my manager: public List<string> addTemporary(string username, string meterNaam, string readingType, string parentID) { Meter meter = new Meter(); VO_Object voObject = objectManager.getObjectByID(parentID); ObjectMeter objMeter = new ObjectMeter(); meter.readingType = (int)Enum.Parse(typeof(ReadingType), readingType); meter.isActive = true; meter.name = meterNaam; meter.startDate = DateTime.Now; meter.endDate = DateTime.Now.AddYears(6000); meter.uniqueIdentifier = "N/A"; meter.meterType = (int)Enum.Parse(typeof(MeterType), "NA"); meter.meterCategory = (int)Enum.Parse(typeof(MeterCategory), "NA"); meter.energyType = (int)Enum.Parse(typeof(EnergyType), "NA"); meter.utilityType = (int)Enum.Parse(typeof(UtilityType), "NA"); meter.unitOfMeasure = (int)Enum.Parse(typeof(UnitOfMeasure), "NA"); objMeter.valid_from = meter.startDate; objMeter.valid_until = meter.endDate; objMeter.Meter = meter; objMeter.VO_Object = voObject; createMeter(meter); List<String> str = new List<string>(); str.Add("" + meter.meterID); str.Add(meter.name); return str; } and this in my Dao Class which links to the database: internal void CreateMeter(Meter _meter) { _entities.AddToMeter(_meter); _entities.SaveChanges(); } Can someone please explain this error? Ronald

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• Is it possible with dynamic TSQL query ?

  - by eugeneK

  I have very long select query which i need to filter based on some params, i'm trying to avoid having different stored procedures or if statements inside of single stored procedure by using partly dynamic TSQL... I will avoid long select just for example sake select a from b where c=@c or d=@d @c and @d are filter params, only one can filter at the same time but also both filters could be disabled. 0 for each of these means param is disables so i can create nvarchar with where statement in it... How do i integrate in here dynamic query so 'where' can be added to normal query. I cannot add all the query as big nvarchar because there is too many things in it which will require changes ( ie. when's, subqueries, joins)

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• Changing newid() to newsequentialid() on an existing table

  - by cbp

  Hi, At the moment we have a number of tables that are using newid() on the primary key. This is causing large amounts of fragmentation. So I would like to change the column to use newsequentialid() instead. I imagine that the existing data will remain quite fragmented but the new data will be less fragmented. This would imply that I should perhaps wait some time before changing the PK index from non-clustered to clustered. My question is, does anyone have experience doing this? Is there anything I have overlooked that I should be careful of?

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• Selecting More Than 1 Table in A Single Query

  - by Kamran

  I have 5 Tables in MS Access as Logs [Title, ID, Date, Author] Tape [Title, ID, Date, Author] Maps [Title, ID, Date, Author] VCDs [Title, ID, Date, Author] Book [Title, ID, Date, Author] I tried my level best through this code SELECT Logs.[Author], Tape.[Author], Maps.[Author], VCDs.[Author], Book.[Author] FROM Logs , Tape , Maps , VCDs, Book WHERE ((([Author] & " " & [Author] & " " & [Author] & " " & [Author]& " " & [Author]) Like "*" & [Type the Title or Any Part of the Title and Press Ok] & "*")); I want to select all of these fields in a single query. Suppose there is Adam as author of works in all tables. So when i put Adam in search box it should result from all tables. I know this can be done by having single table or renaming fields names but that's not required. Please help.

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• How do I get every nth row in a table, or how do I break up a subset of a table into sets or rows of

  - by Jherico

  I have a table of heterogeneous pieces of data identified by a primary key (ID) and a type identifier (TYPE_ID). I would like to be able to perform a query that returns me a set of ranges for a given type broken into even page sizes. For instance, if there are 10,000 records of type '1' and I specify a page size of 1000, I want 10 pairs of numbers back representing values I can use in a BETWEEN clause in subsequent queries to query the DB 1000 records at a time. My initial attempt was something like this select id, rownum from CONTENT_TABLE where type_id = ? and mod(rownum, ?) = 0 But this doesn't work.

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• counting employee attendance

  - by jjj

  i am trying to write a statment for counting the employees attendance and execute thier id , name and the days that he has working on the last 3 months by counting the duplicate id on NewTimeAttendance for month 1 , 2 and 3 .. i tried to count : Select COUNT(employeeid) from NewTimeAttendance where employeeid=1 and (month=1 or month =2 or month = 3) This is absolutely working ,but just for one employee... the secound try: SELECT COUNT(NewEmployee.EmployeeID) FROM NewEmployee INNER JOIN NewTimeAttendance ON NewEmployee.EmployeeID = NewTimeAttendance.EmployeeID and (month=1 or month =2 or month = 3) This is working , but it counts all employees .. and i want it to execute each EmployeeId, EmployeeName and number of days as new record last try: (before you see the code ... it is wrong ..but i am trying) for i in 0..27 loop SELECT COUNT(NewEmployee.EmployeeID),NewEmployee.EmployeeId,EmployeeName FROM NewEmployee INNER JOIN NewTimeAttendance ON NewEmployee.EmployeeID(i) = NewTimeAttendance.EmployeeID and (month=1 or month =2 or month = 3) end loop i realy need help...thanks in advance

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• writting an sql query

  - by Praveen Prasad

  iam having 2 tables table Items Table (this table holds all items iam having) itemId --------- Item1 Item2 Item3 Item4 Item5 table 2 users_item relation UserId || ItemId 1 || Item1 1 || Item2 userId one has stored 2 items Item1,Item2. Now i want to write a query on table1 (Items table) so that it displays all items which user1 has NOT chosen.

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• count(*) vs count(row-name) - which is more correct?

  - by bread

  Does it make a difference if you do count(*) vs count(row-name) as in these two examples? I have a tendency to always write count(*) because it seems to fit better in my mind with the notion of it being an aggregate function, if that makes sense. But I'm not sure if it's technically best as I tend to see example code written without the * more often than not. count(*): select customerid, count(*), sum(price) from items_ordered group by customerid having count(*) > 1; vs. count(row-name): SELECT customerid, count(customerid), sum(price) FROM items_ordered GROUP BY customerid HAVING count(customerid) > 1;

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• Count total number of callers?

  - by Kristopher Ives

  I'm currently doing this query to find the guy who makes the most calls: SELECT `commenter_name`, COUNT(*) AS `calls` FROM `comments` GROUP BY `commenter_name` ORDER BY `calls` LIMIT 1 What I want now is to be able to find out how many total unique callers. I tried using DISTINCT but I didn't get anywhere.

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• How to SUM columns on multiple conditions in a GROUP BY

  - by David Liddle

  I am trying to return a list of Accounts with their Balances, Outcome and Income Account Transaction ------- ----------- AccountID TransactionID BankName AccountID Locale Amount Status Here is what I currently have. Could someone explain where I am going wrong? select a.ACCOUNT_ID, a.BANK_NAME, a.LOCALE, a.STATUS, sum(t1.AMOUNT) as BALANCE, sum(t2.AMOUNT) as OUTCOME, sum(t3.AMOUNT) as INCOME from ACCOUNT a left join TRANSACTION t1 on t1.ACCOUNT_ID = a.ACCOUNT_ID left join TRANSACTION t2 on t1.ACCOUNT_ID = a.ACCOUNT_ID and t2.AMOUNT < 0 left join TRANSACTION t3 on t3.ACCOUNT_ID = a.ACCOUNT_ID and t3.AMOUNT > 0 group by a.ACCOUNT_ID, a.BANK_NAME, a.LOCALE, a.[STATUS]

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• Access is refusing to run an query with linked table?

  - by Mahmoud

  Hey all i have 3 tables each as follow cash_credit Bank_Name-------in_date-------Com_Id---Amount America Bank 15/05/2010 1 200 HSBC 17/05/2010 3 500 Cheque_credit Bank_Name-----Cheque_Number-----in_date-------Com_Id---Amount America Bank 74835435-5435 15/05/2010 2 600 HSBC 41415454-2851 17/05/2010 5 100 Companies com_id----Com_Name 1 Ebay 2 Google 3 Facebook 4 Amazon Companies table is a linked table when i tried to create an query as follow SELECT cash_credit.Amount, Companies.Com_Name, cheque_credit.Amount FROM cheque_credit INNER JOIN (cash_credit INNER JOIN Companies ON cash_credit.com_id = Companies.com_id) ON cheque_credit.com_id = Companies.com_id; I get an error saying that my inner Join is incorrectly, this query was created using Access 2007 query design the error is Type mismatch in expression then i thought it might be the inner join so i tried Left Join and i get an error that this method is not used JOIN expression is not supported I am confused on where is the problem that is causing all this

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• Insert not working

  - by user1642318

  I've searched evreywhere and tried all suggestions but still no luck when running the following code. Note that some code is commented out. Thats just me trying different things. SqlConnection connection = new SqlConnection("Data Source=URB900-PC\SQLEXPRESS;Initial Catalog=usersSQL;Integrated Security=True"); string password = PasswordTextBox.Text; string email = EmailTextBox.Text; string firstname = FirstNameTextBox.Text; string lastname = SurnameTextBox.Text; //command.Parameters.AddWithValue("@UserName", username); //command.Parameters.AddWithValue("@Password", password); //command.Parameters.AddWithValue("@Email", email); //command.Parameters.AddWithValue("@FirstName", firstname); //command.Parameters.AddWithValue("@LastName", lastname); command.Parameters.Add("@UserName", SqlDbType.VarChar); command.Parameters["@UserName"].Value = username; command.Parameters.Add("@Password", SqlDbType.VarChar); command.Parameters["@Password"].Value = password; command.Parameters.Add("@Email", SqlDbType.VarChar); command.Parameters["@Email"].Value = email; command.Parameters.Add("@FirstName", SqlDbType.VarChar); command.Parameters["@FirstName"].Value = firstname; command.Parameters.Add("@LasttName", SqlDbType.VarChar); command.Parameters["@LasttName"].Value = lastname; SqlCommand command2 = new SqlCommand("INSERT INTO users (UserName, Password, UserEmail, FirstName, LastName)" + "values (@UserName, @Password, @Email, @FirstName, @LastName)", connection); connection.Open(); command2.ExecuteNonQuery(); //command2.ExecuteScalar(); connection.Close(); When I run this, fill in the textboxes and hit the button I get...... Must declare the scalar variable "@UserName". Any help would be greatly appreciated. Thanks.

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• Aggregate Functions in Index with IBMDB2

  - by Erkan

  Is there any way to pre aggregate results of aggregate functionts (f.i. count()) and store it in an index? The background is: i want to speed up count() queries. So that: Select count(users) from TE123 where region = 'A'; would be supported by an index like Region Count(Users) A 548 E 458 I know that MQTs would also help for this problem. However, in this case it is not possible to use MQT, as we use kind of an ORM and we don't want to define Entities on MQTs. I just slightly remember - one DBA told me - that there is such a function planned for DB2 V10.

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• Oracle : select maximum value from different comulms of the same row

  - by gregseth

  The whole question is pretty much in the title. For each row of the table I'd like to select the maximum of a subset of columns. For example, from this table name m1 m2 m3 m4 A 1 2 3 4 B 6 3 4 5 C 1 5 2 1 the result would be name max A 4 B 6 C 5 The query must be compatible oracle 8i. Thanks.

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• C# - Password Database

  - by user335932

  So I want to make a program that allows you to store and search for user names/passwords for online sites there signed up to. I know C# has some database options but I don't know much about it. I also heard that it can read/write excel files. Whats do you think is best for storing the data? ALSO do databases need to be stored online on a sever, or can they reside in the program files?

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• ms-access: difference between control source and row source

  - by every_answer_gets_a_point

  i have learning reports in access and i don't understand the difference between these two concepts. i understand that the control source is the column? but then what is the row source?

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• Concurrent usage of table causing issues

  - by Sven

  Hello In our current project we are interfacing with a third party data provider. They need to insert data in a table of ours. This inserting can be frequent every 1 min, every 5min, every 30, depends on the amount of new data they need to provide. The use the isolation level read committed. On our end we have an application, windows service, that calls a webservice every 2 minutes to see if there is new data in this table. Our isolation level is repeatable read. We retrieve the records and update a column on these rows. Now the problem is that sometimes this third party provider needs to insert a lot of data, let's say 5000 records. They do this per transaction (5rows per transaction), but they don't close the connection. They do one transaction and then the next untill all records are inserted. This caused issues for our process, we receive a timeout. If this goes on for a long time the database get's completely unstable. For instance, they maybe stopped, but the table somehow still stays unavailable. When I try to do a select on the table, I get several records but at a certain moment I don't get any response anymore. It just says retrieving data but nothing comes anymore until I get a timeout exception. Only solution is to restart the database and then I see the other records. How can we solve this. What is the ideal isolation level setting in this scenario?

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