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  • Does normalization really hurt performance in high traffic sites?

    - by Luke101
    I am designing a database and I would like to normalize the database. I one query I will joining about 30-40 tables. Will this hurt the website performance if it ever becomes extremely popular? This will be the main query and it will be getting called 50% of the time. The other queries I will be joining about 2 tables. I have a choice right now to normalize or not to normalize but if the normalization becomes a problem in the future i may have to rewrite 40% of the software and it may take me a long time. Does normalization really hurt in this case? Should I denormalize now while I have the time?

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  • Round date to 10 minutes interval

    - by Peter Lang
    I have a DATE column that I want to round to the next-lower 10 minute interval in a query (see example below). I managed to do it by truncating the seconds and then subtracting the last digit of minutes. WITH test_data AS ( SELECT TO_DATE('2010-01-01 10:00:00', 'YYYY-MM-DD HH24:MI:SS') d FROM dual UNION SELECT TO_DATE('2010-01-01 10:05:00', 'YYYY-MM-DD HH24:MI:SS') d FROM dual UNION SELECT TO_DATE('2010-01-01 10:09:59', 'YYYY-MM-DD HH24:MI:SS') d FROM dual UNION SELECT TO_DATE('2010-01-01 10:10:00', 'YYYY-MM-DD HH24:MI:SS') d FROM dual UNION SELECT TO_DATE('2099-01-01 10:00:33', 'YYYY-MM-DD HH24:MI:SS') d FROM dual ) -- #end of test-data SELECT d, TRUNC(d, 'MI') - MOD(TO_CHAR(d, 'MI'), 10) / (24 * 60) FROM test_data And here is the result: 01.01.2010 10:00:00    01.01.2010 10:00:00 01.01.2010 10:05:00    01.01.2010 10:00:00 01.01.2010 10:09:59    01.01.2010 10:00:00 01.01.2010 10:10:00    01.01.2010 10:10:00 01.01.2099 10:00:33    01.01.2099 10:00:00 Works as expected, but is there a better way? EDIT: I was curious about performance, so I did the following test with 500.000 rows and (not really) random dates. I am going to add the results as comments to the provided solutions. DECLARE t TIMESTAMP := SYSTIMESTAMP; BEGIN FOR i IN ( WITH test_data AS ( SELECT SYSDATE + ROWNUM / 5000 d FROM dual CONNECT BY ROWNUM <= 500000 ) SELECT TRUNC(d, 'MI') - MOD(TO_CHAR(d, 'MI'), 10) / (24 * 60) FROM test_data ) LOOP NULL; END LOOP; dbms_output.put_line( SYSTIMESTAMP - t ); END; This approach took 03.24 s.

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  • choose append to existing backup instead of overwrite

    - by aron
    Hello, I have a database and I made it's first backup 2 days ago. Then yesterday I spent an entire adding new records. This morning I ran a backup, (but I selected append to existing backup set) as pictured below. I just ran a restore and I found that it wiped out all my data from yesterday and it restored it from the backup of 2 days ago. Not the version from this mornings backup. I zipped this backup file to be safe. I changed some data in the DB, Then I ran the back up again, but this time I selected "overwrite all existing backup sets" Now when I restore the db it's seems to restore the data from the backup correctly. I think I learned a lesson here, correctly if I'm wrong My questions is, Did I lose an entire day of work? I still have this morning's backup .bak file safe in a zip. Is there anyway I can restore is with the right data?

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  • update query with join on two tables

    - by dba_query
    I have customer and address tables. query: select * from addresses a, customers b where a.id = b.id returns 474 records For these records, I'd like to add the id of customer table into cid of address table. Example: If for the first record the id of customer is 9 and id of address is also 9 then i'd like to insert 9 into cid column of address table. I tried: update addresses a, customers b set a.cid = b.id where a.id = b.id but this does not seem to work.

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  • Check for active connection in NHibernate

    - by Dofs
    I have a system with a few different databases, and I would like to check if a certain database is down, and if so display a message to the user. Is it possible in NHibernate to check if there is an active connection to the database, without having to request data and then catch the exception?

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  • Alternative to subqueries

    - by Juanma
    I'm using Mysql 5.1, and have this query, is there a way to not use the subqueries and accomplish the same result? SELECT oref.affiliate_id, ROUND(sum( oph.amount ) * 0.10 ,2) AS tsum FROM operators_referer AS oref LEFT JOIN operators_payments_history AS oph ON oref.operator_id = oph.operator_id WHERE oref.affiliate_id = 28221 AND ( oph.date_paid > ( SELECT MAX(aph.date_paid) FROM affiliates_payments_history AS aph WHERE aph.operator_id = oref.affiliate_id ) OR ( SELECT MAX(aph.date_paid) FROM affiliates_payments_history AS aph WHERE aph.operator_id = oref.affiliate_id ) is NULL )

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  • Accessing an Access DB from Outlook via VBA

    - by camastanta
    Hi The situation: In Outlook I get a message from a server. The content of the message needs to be put into an Access db. But, there may not exist another message with the same date. So, I need to look into a db if there is already a message with the same date and time. If there exists one, then it needs to be replaced and otherwise the message needs to be added to the database. The database contains a list of current positions from the vehicles on the road. The problem: I have problems to compare a date time with a date time in an Access DB via VBA. The query I use returns no records but there is a record in the database. This is the query I use: adoRS.Open "SELECT * FROM currentpositions WHERE ((currentpositions. [dateLT])=" & "#" & date_from_message & "#" & ")", adoConn, adOpenStatic, adLockOptimistic Second I need to now what the result is of that query. How can I determine the number of records that my query gives me? Thanks camastanta

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  • SQL query INSERT not working inserting values into my DB.

    - by Aiden Ryan
    Hello, I'm trying to insert registration data into a database but my php code isn't inserting the values into the DB although I'm not getting any errors either, can someone help me? this is the code i'm currently using: $connect = mysql_connect("localhost","myusername","mypassword"); mysql_select_db("application"); $queryreg = mysql_query('INSERT INTO users("username","password","email","date") VALUES("$username","$password","$email","$date")'); die ("You Have Been Registered."); I just need to add the username password email and date into the fields i have specified but it won't work, please someone help!

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  • Sybase ASA 8.0 trigger how to determine whether to insert ,update,delete operate.

    - by guaike
    Follow is my trigger of Sybase ASA 8.0 script: Create trigger dba.test after insert,delete,update order 1 on DBA.tb_press referencing old as _old new as _new for each row begin --How to detect deleteOperate,updateOperate? if deleteOperate then insert into syncLog(tableName,keyId,version,operate) select tb_press,_old.id,1,'delete' end if; end how to determine whether to insert ,update,delete operate.

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  • Avoiding repeated subqueries when 'WITH' is unavailable

    - by EloquentGeek
    MySQL v5.0.58. Tables, with foreign key constraints etc and other non-relevant details omitted for brevity: CREATE TABLE `fixture` ( `id` int(11) NOT NULL auto_increment, `competition_id` int(11) NOT NULL, `name` varchar(50) NOT NULL, `scheduled` datetime default NULL, `played` datetime default NULL, PRIMARY KEY (`id`) ); CREATE TABLE `result` ( `id` int(11) NOT NULL auto_increment, `fixture_id` int(11) NOT NULL, `team_id` int(11) NOT NULL, `score` int(11) NOT NULL, `place` int(11) NOT NULL, PRIMARY KEY (`id`) ); CREATE TABLE `team` ( `id` int(11) NOT NULL auto_increment, `name` varchar(50) NOT NULL, PRIMARY KEY (`id`) ); Where: A draw will set result.place to 0 result.place will otherwise contain an integer representing first place, second place, and so on The task is to return a string describing the most recently played result in a given competition for a given team. The format should be "def Team X,Team Y" if the given team was victorious, "lost to Team X" if the given team lost, and "drew with Team X" if there was a draw. And yes, in theory there could be more than two teams per fixture (though 1 v 1 will be the most common case). This works, but feels really inefficient: SELECT CONCAT( (SELECT CASE `result`.`place` WHEN 0 THEN "drew with" WHEN 1 THEN "def" ELSE "lost to" END FROM `result` WHERE `result`.`fixture_id` = (SELECT `fixture`.`id` FROM `fixture` LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id` WHERE `fixture`.`competition_id` = 2 AND `result`.`team_id` = 1 ORDER BY `fixture`.`played` DESC LIMIT 1) AND `result`.`team_id` = 1), ' ', (SELECT GROUP_CONCAT(`team`.`name`) FROM `fixture` LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id` LEFT JOIN `team` ON `result`.`team_id` = `team`.`id` WHERE `fixture`.`id` = (SELECT `fixture`.`id` FROM `fixture` LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id` WHERE `fixture`.`competition_id` = 2 AND `result`.`team_id` = 1 ORDER BY `fixture`.`played` DESC LIMIT 1) AND `team`.`id` != 1) ) Have I missed something really obvious, or should I simply not try to do this in one query? Or does the current difficulty reflect a poor table design?

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  • How do I go about link web content in a database with a nested set model?

    - by wb
    My nested set table is as follows. create table depts ( id int identity(0, 1) primary key , lft int , rgt int , name nvarchar(60) , abbrv nvarchar(20) ); Test departments. insert into depts (lft, rgt, name, abbrv) values (1, 14, 'root', 'r'); insert into depts (lft, rgt, name, abbrv) values (2, 3, 'department 1', 'd1'); insert into depts (lft, rgt, name, abbrv) values (4, 5, 'department 2', 'd2'); insert into depts (lft, rgt, name, abbrv) values (6, 13, 'department 3', 'd3'); insert into depts (lft, rgt, name, abbrv) values (7, 8, 'sub department 3.1', 'd3.1'); insert into depts (lft, rgt, name, abbrv) values (9, 12, 'sub department 3.2', 'd3.2'); insert into depts (lft, rgt, name, abbrv) values (10, 11, 'sub sub department 3.2.1', 'd3.2.1'); My web content table is as follows. create table content ( id int identity(0, 1) , dept_id int , page_name nvarchar(60) , content ntext ); Test content. insert into content (dept_id, page_name, content) values (3, 'index', '<h2>welcome to department 3!</h2>'); insert into content (dept_id, page_name, content) values (4, 'index', '<h2>welcome to department 3.1!</h2>'); insert into content (dept_id, page_name, content) values (6, 'index', '<h2>welcome to department 3.2.1!</h2>'); insert into content (dept_id, page_name, content) values (2, 'what-doing', '<h2>what is department 2 doing?/h2>'); I'm trying to query the correct page content (from the content table) based on the url given. I can easily accomplish this task with a root department. However, querying a department with multiple depths is proving to be a little harder. For example: http://localhost/departments.asp?d3/ (Should return <h2>welcome to department 3!</h2>) http://localhost/departments.asp?d2/what-doing (Should return <h2>what is department 2 doing?</h2>) I'm not sure if this can be create in one query or if there will need to be a recursive function of some sort. Also, if there is nothing after the last / then assume we want the index page. How can this be accomplished? Thank you.

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  • data filter using dataloadoptions

    - by Tassadaque
    Using dataloadoptions i have tried the following example Northwnd db = new Northwnd(@"northwnd.mdf"); // Preload Orders for Customer. // One directive per relationship to be preloaded. DataLoadOptions ds = new DataLoadOptions(); ds.LoadWith<Customer>(c => c.Orders); ds.AssociateWith<Customer> (c => c.Orders.Where(p => p.ShippedDate != DateTime.Today)); db.LoadOptions = ds; var custQuery = from cust in db.Customers where cust.City == "London" select cust; foreach (Customer custObj in custQuery) { Console.WriteLine("Customer ID: {0}", custObj.CustomerID); foreach (Order ord in custObj.Orders) { Console.WriteLine("\tOrder ID: {0}", ord.OrderID); foreach (OrderDetail detail in ord.OrderDetails) { Console.WriteLine("\t\tProduct ID: {0}", detail.ProductID); } } } Now i need to ask how can i display Category ID and Category Name of the productID (i am supposing that One product can be in at most one category) by extending the above example Regards

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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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  • Looking for MSSQL Table Design Sanity Check for Profile Tables with Dynamic Columns.

    - by Code Sherpa
    I just want a general sanity check regarding database design. We are building a web system that has both Teachers and Students. Both have accounts in the system. Both have profiles in the system. My question is about the table design of those Profile tables. The Teacher profile is pretty static regarding the metadata associated with it. Each teacher has a set number of fields that exposes information about that individual (schools, degrees, etc). The students, however, are a different case. We are using a windows service to pull varying data about the students from an endless stream of excel spreadsheets. The data gets moved into our database and then the fields appear in association with the student's profile. Accordingly, each and every student may have very different fields in their profile. I originally started with the concept of three tables: Accounts ---------- AccountID TeacherProfiles ---------- TeacherProfileID AccountID SecondarySchool University YearsTeaching Etc... StudentProfiles ---------- StudentProfileID AccountID Header Value The StudentProfiles table would hold the name of the column headers from the excel spreadsheets and the associated values. I have since evolved the design a little to treat Profiles more generically per the attached ERD image. The Teacher and Student "Headers" are stored in a table called "ProfileAttributeTypes" and responses (either from the excel document or via input fields on the web form) are put in a ProfileAttributes table. This way both Student and Teacher profiles can be associated with a dynamic flow of profile fields. The "Permissions" table tells us whether we are dealing with a Student or a Teacher. Since this system is likely to grow quickly, I want to make sure the foundation is solid. Can you please provide feedback about this design and let me know if it seems sound or if you could see problems it might create and, if so, what might be a better approach? Thanks in advance.

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  • Foreign Keys and Primary Keys at the same time

    - by Bader
    hello , i am trying to create table (orderdetails) , the table has two FKs and PKs at the same keys here is my code create table OrderDetails2 ( PFOrder_ID Number(3) PFProduct_ID Number(3) CONSTRAINT PF PRIMARY KEY (PFOrder_ID,PFProduct_ID), CONSTRAINT FK_1 FOREIGN KEY (PFProudct_ID) REFERENCES Product(Product_ID), CONSTRAINT FK_2 FOREIGN KEY (PFOrder_ID) REFERENCES Orderr(Order_ID) ); i am using Oracle express , a problem pops when i run the code , here is it ORA-00907: missing right parenthesis what is the problem ?

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  • Copy new records from datatable and identify changes in old records

    - by Betite
    Assume there are two tables: Remote_table and My_table. Remote_table has 6 columns: **PROJECT JOB_TYPE MONTH YEAR** HOURS IS_DELETED 134393 70 1 2013 30 0 134393 70 2 2013 50 0 134393 70 3 2013 80 0 134393 70 10 2012 10 0 134393 70 11 2012 0 0 134393 70 12 2012 15 0 My_table is a copy of remote_table. I tried to copy only the new records from the remote_table by this query: SELECT * FROM [remote_DB].[LudanProjectManager].[dbo].Remote_table EXCEPT SELECT * FROM My_table It works OK but I get a duplicate primary key exception when changes have been made on the remote_table on the hours column. Can anyone think of a way to copy only the new records from remote_table and if changes has been made on old records, to identify them and update the my_table to correspond?

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