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  • Circular database relationships. Good, Bad, Exceptions?

    - by jim
    I have been putting off developing this part of my app for sometime purely because I want to do this in a circular way but get the feeling its a bad idea from what I remember my lecturers telling me back in school. I have a design for an order system, ignoring the everything that doesn't pertain to this example I'm left with: CreditCard Customer Order I want it so that, Customers can have credit cards (0-n) Customers have orders (1-n) Orders have one customer(1-1) Orders have one credit card(1-1) Credit cards can have one customer(1-1) (unique ids so we can ignore uniqueness of cc number, husband/wife may share cc instances ect) Basically the last part is where the issue shows up, sometimes credit cards are declined and they wish to use a different one, this needs to update which their 'current' card is but this can only change the current card used for that order, not the other orders the customer may have on disk. Effectively this creates a circular design between the three tables. Possible solutions: Either Create the circular design, give references: cc ref to order, customer ref to cc customer ref to order or customer ref to cc customer ref to order create new table that references all three table ids and put unique on the order so that only one cc may be current to that order at any time Essentially both model the same design but translate differently, I am liking the latter option best at this point in time because it seems less circular and more central. (If that even makes sense) My questions are, What if any are the pros and cons of each? What is the pitfalls of circular relationships/dependancies? Is this a valid exception to the rule? Is there any reason I should pick the former over the latter? Thanks and let me know if there is anything you need clarified/explained. --Update/Edit-- I have noticed an error in the requirements I stated. Basically dropped the ball when trying to simplify things for SO. There is another table there for Payments which adds another layer. The catch, Orders can have multiple payments, with the possibility of using different credit cards. (if you really want to know even other forms of payment). Stating this here because I think the underlying issue is still the same and this only really adds another layer of complexity.

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  • Best way to get a reasonably random key for MYSQL records

    - by Steve N
    Hi there, I need to generate a reasonably random unique key for a table. It should be something like a GUID for MYSQL. I've tried UUID, but it looks like only the first few characters are actually random- the rest are the same every time I insert them. Essentially, it is desirable for this key field to be very difficult to guess, even if you already have one known value in the column. What is the best way to do this, and how should I set up the field data type to store the value efficiently? Thank you, Steve

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  • Slow query with unexpected scan

    - by zerkms
    Hello I have this query: SELECT * FROM SAMPLE SAMPLE INNER JOIN TEST TEST ON SAMPLE.SAMPLE_NUMBER = TEST.SAMPLE_NUMBER INNER JOIN RESULT RESULT ON TEST.TEST_NUMBER = RESULT . TEST_NUMBER WHERE SAMPLED_DATE BETWEEN '2010-03-17 09:00' AND '2010-03-17 12:00' the biggest table here is RESULT, contains 11.1M records. The left 2 tables about 1M. this query works slowly (more than 10 minutes) and returns about 800 records. executing plan shows clustered index scan over all 11M records. RESULT.TEST_NUMBER is a clustered primary key. if I change 2010-03-17 09:00 to 2010-03-17 10:00 - i get about 40 records. it executes for 300ms. and plan shows clustered index seek if i replace * in SELECT clause to RESULT.TEST_NUMBER (covered with index) - then all become fast in first case too. this points to hdd io issues, but doesn't clarifies changing plan. so, any ideas?

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  • Can in-memory SQLite databases scale with concurrency?

    - by Kent Boogaart
    In order to prevent a SQLite in-memory database from being cleaned up, one must use the same connection to access the database. However, using the same connection causes SQLite to synchronize access to the database. Thus, if I have many threads performing reads against an in-memory database, it is slower on a multi-core machine than the exact same code running against a file-backed database. Is there any way to get the best of both worlds? That is, an in-memory database that permits multiple, concurrent calls to the database?

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  • Padding a string in Postgresql with rpad without truncating it

    - by dmoebius
    Using Postgresql 8.4, how can I right-pad a string with blanks without truncating it when it's too long? The problem is that rpad truncates the string when it is actually longer than number of characters to pad. Example: SELECT rpad('foo', 5); ==> 'foo ' -- fine SELECT rpad('foo', 2); ==> 'fo' -- not good, I want 'foo' instead. The shortest solution I found doesn't involve rpad at all: SELECT 'foo' || repeat(' ', 5-length('foo')); ==> 'foo ' -- fine SELECT 'foo' || repeat(' ', 2-length('foo')); ==> 'foo' -- fine, too but this looks ugly IMHO. Note that I don't actually select the string 'foo' of course, instead I select from a column: SELECT colname || repeat(' ', 30-length(colname)) FROM mytable WHERE ... Is there a more elegant solution?

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  • Installing databases after installation of server.

    - by claws
    Hello, I my software I need the client to install a database server (MySQL in my case). I'm deploying the setup and making user install it like a pre-requisite. After installing the DBMS server. I need to setup databases (that I created) on the client machine. How to do this automatically (as part of installation.)?

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  • select from multiple tables but ordering by a datetime field

    - by Chris Mccabe
    I have 3 tables that are unrelated (related that each contains data for a different social network). Each has a datetime field dated- I'm already grouping by hour as you can see below (this one below for linked_in) SELECT count(*), date_format(dated, '%Y:%m:%d %H') as hour FROM upd8r_linked_in_accts WHERE CAST(dated AS DATE) = '".$start_date."' GROUP BY hour I would like to know how to do a total across all 3 networks- the tables for the three are CREATE TABLE IF NOT EXISTS `upd8r_facebook_accts` ( `id` int(11) NOT NULL AUTO_INCREMENT, `owner_id` varchar(50) NOT NULL, `user_id` int(11) NOT NULL, `fb_id` bigint(30) NOT NULL, `dated` datetime NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=80 ; CREATE TABLE IF NOT EXISTS `upd8r_linked_in_accts` ( `id` int(11) NOT NULL AUTO_INCREMENT, `owner_id` varchar(50) NOT NULL, `user_id` int(11) NOT NULL, `linked_in` varchar(200) NOT NULL, `oauth_secret` varchar(100) NOT NULL, `first_count` int(11) NOT NULL, `second_count` int(11) NOT NULL, `dated` datetime NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=200 ; CREATE TABLE IF NOT EXISTS `upd8r_twitter_accts` ( `id` int(11) NOT NULL AUTO_INCREMENT, `owner_id` varchar(50) NOT NULL, `user_id` int(11) NOT NULL, `twitter` varchar(200) NOT NULL, `twitter_secret` varchar(100) NOT NULL, `dated` datetime NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=9 ; something like this ? (SELECT count(*), date_format(dated, '%Y:%m:%d %H') as hour FROM upd8r_linked_in_accts WHERE CAST(dated AS DATE) = '".$start_date."') UNION ALL (SELECT count(*), date_format(dated, '%Y:%m:%d %H') as hour FROM upd8r_facebook_accts WHERE CAST(dated AS DATE) = '".$start_date."') UNION ALL (SELECT count(*), date_format(dated, '%Y:%m:%d %H') as hour FROM upd8r_twitter_accts WHERE CAST(dated AS DATE) = '".$start_date."') UNION ALL GROUP BY hour

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  • SSRS Dynamic Returning Dataset Collection Field in Expression

    - by Ray Clark
    I wrote a custom assembly to take a parameter value from the report and return a field from the dataset collection. My assembly returns the correct fields!name.value, but it shows me the string representation of it. How can I get it to resolve as the actual fields!name.value to display the actual data in the dataset? If I enter fields!name.value in manually it works fine showing me the value. If I resolve it with my custom code it display "fields!name.value" to me in the cell.

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  • UUID collision risk using different algorithms

    - by Diego Jancic
    Hi Guys, I have a database where 2 (or maybe 3 or 4) different applications are inserting information. The new information has IDs of the type GUID/UUID, but each application is using a different algorithm to generate the IDs. For example, one is using the NHibernate's "guid.comb", other is using the SQLServer's NEWID(), other might want to use .NET's Guid.NewGuid() implementation. Is there an above normal risk of ID collision or duplicates? Thanks!

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  • Custom order in Oracle PL/SQL

    - by Jasim
    I have an oracle query in which and i want the result to be in custom order 'SENIOR DIRECTOR', 'DIRECTOR', 'MANAGER', 'EMPLOYEE' which is from the field GRADE_DESCRIPTON. I am using the below query. However I am not getting the desired result The order of the result im getting is 'SENIOR DIRECTOR','MANAGER', DIRECTOR,'EMPLOYEE' SELECT DISTINCT GRADE_DESCRIPTION, HIRING_FORECATS.* FROM GRADE_MASTER left join IRING_FORECATS ON (HIRING_FORECATS.GRADE = GRADE_MASTER.GRADE_DESCRIPTION and HIRING_FORECATS.LOCATION = 'HO' ) order by decode(GRADE_MASTER.GRADE_DESCRIPTION, 'SENIOR DIRECTOR', 'DIRECTOR', 'MANAGER', 'EMPLOYEE') Any Suggestions??

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  • How can I "merge", "flatten" or "pivot" results from a query which returns multiple rows into a sing

    - by dsm
    I have a simple query over a table, which returns results like the following: id id_type id_ref 2702 5 31 2702 16 14 2702 17 3 2702 40 1 2702 26 4 And I would like to merge the results into a single row, for instance: id concatenation 2702 5,16,17,40,26:31,14,3,1,4 Is there any way to do this within a trigger? NB: I know I can use a cursor, but I would really prefer not to unless there is no better way.

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  • filter by multiple attributes

    - by cosy
    I have the table : id id_products id_atribut name value 1 13 8 autdio 2.1 2 13 9 hdd 200 Gb 3 13 10 cd-rom 2 4 20 8 audio 2.1 the problem is, how can i select from this table where name="audio" and value="2.1" and name="hdd" and value="200 gb" and return id_products=13 .... How can i do this?

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  • Android quotes within an sql query string

    - by miannelle
    I want to perform a query like the following: uvalue = EditText( some user value ); p_query = "select * from mytable where name_field = '" + uvalue + "'" ; mDb.rawQuery( p_query, null ); if the user enters a single quote in their input it crashes. If you change it to: p_query = "select * from mytable where name_field = \"" + uvalue + "\"" ; it crashes if the user enters a double quote in their input. and of course they could always enter both single and double quotes.

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  • Need help with REGEXP_REPLACE

    - by Randy
    hey regex guru's I have a data column that contains a substring similar to this: 'This is a string with ID=123 contained inside' i need to replace the ID=123 with another fixed string say ID=1 i have a working REPLACE call that swaps out the values correctly, but this only works on a known original id number. I can extend to make it work when the number of digits are known by using some substr magic, however, the id number may have an arbitrary number of digits, so i'm thinking regex. any help with the regex magix to grab the entire ID=999 substring no matter how many digits would be very helpful. thanks

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  • What are the Pros and Cons of Cascading delete and updates?

    - by Misnomer
    Hi, Maybe this is sort of a naive question...but I think that we should always have cascading deletes and updates. But I wanted to know are there problems with it and when should we should not do it? I really can't think of a case right now where you would not want to do an cascade delete but I am sure there is one...but what about updates should they be done always? So can anyone please list out the pros and cons of cascading deletes and updates ? Thanks.

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  • SQLParameter not working properly

    - by Pselus
    I am trying to access a stored procedure and I'm getting an error that says: Procedure or function 'getbug' expects parameter '@bugID', which was not supplied. This is my code to call the procedure. SqlCommand cmd = new SqlCommand("getbug", cn); cmd.Parameters.Add(new SqlParameter("bugID", bugID)); bugID is set as 1089 (and is type int) I can't figure out why this won't work.

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  • NHibernate Many-to-Many Mapping not working

    - by ClutchDude
    I have a Nhibernate mapping file for a simple user/role mapping. Here are the mapping files: Users.hbm.xml <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Sample.Persistence" namespace="Sample.Persistence.Model"> <class name="User" table="Users"> <id name="UserKey"> <generator class="identity"/> </id> <property name="UserName" column="UserName" type="String" /> <property name="Password" column="Password" type="Byte[]" /> <property name="FirstName" column="FirstName" type="String" /> <property name="LastName" column="LastName" type="String" /> <property name="Email" column="Email" type="String" /> <property name="Active" column="Active" type="Boolean" /> <property name="Locked" column="Locked" type="Boolean" /> <property name="LoginFailures" column="LoginFailures" type="int" /> <property name="LockoutDate" column="LockoutDate" type="DateTime" generated="insert" /> <property name="Expired" column="Expired" type="Boolean" generated="insert"/> <set name="Roles" table="UsersRolesBridge" lazy="false"> <key column="UserKey" /> <many-to-many class="Role" not-found="exception" column="RoleKey" /> </set> </class> </hibernate-mapping> Role.hbm.xml <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Sample.Persistence" namespace="Sample.Persistence.Model"> <class name="Role" table="Roles"> <id name="RoleKey"> <generator class="identity"/> </id> <property name="Name" column="Name" type="String" /> <set name="Users" inverse="true" atable="UsersRolesBridge" lazy="false" > <key column="RoleKey" /> <many-to-many class="User" column="UserKey" /> </set> </class> </hibernate-mapping> I am able to retrieve roles for each user via NHibernate but when I go to save a new object, the roles are not saved in the Bridge table. The user is created and insert with no issues. I've checked that the Role collection, a field on the user, is being populated with the proper rolekey before the Session.Save() is called. There is no exception thrown as well.

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  • .NET/C# Drizzle database client

    - by FlappySocks
    I am planning to use Drizzle in my next C# Mono app. Since there is no C# client available for Drizzle, I thought I would have a stab at writing my own by converting the Java client, and then making it work with DBLinq. Having seen the Java client, I realise that it's a longer job that I had anticipated, and I don't have the time. Besides the Java client is not all that mature yet. Since there is an official Drizzle C client library (libdrizzle), writing a C# wrapper might be the best solution. Are there any tools available that can assist in generating the code for this?

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  • Best method to search hierarchical data

    - by WDuffy
    I'm looking at building a facility which allows querying for data with hierarchical filtering. I have a few ideas how I'm going to go about it but was wondering if there are any recommendations or suggestions that might be more efficient. As an example imagine that a user is searching for a job. The job areas would be as follows. 1: Scotland 2: --- West Central 3: ------ Glasgow 4: ------ Etc 5: --- North East 6: ------ Ayrshire 7: ------ Etc A user can search specific (i.e. Glasgow) or in a larger area (i.e. Scotland). The two approaches I am considering are: keep a note of children in the database for each record (i.e. cat 1 would have 2, 3, 4 in its children field) and query against that record with a SELECT * FROM Jobs WHERE Category IN Areas.childrenField. Use a recursive function to find all results who have a relation to the selected area. The problems I see from both are: Holding this data in the db will mean having to keep track of all changes to structure. Recursion is slow and inefficent. Any ideas, suggestion or recommendations on the best approach? I'm using C# ASP.NET with MSSQL 2005 DB.

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  • performing more than one Where in query return null!!! why? how to fix this?

    - by Sadegh
    hi, i have wrote a method that filters output with provided query and return it. when one Where excuted; it return correct output but when more than one Where excuted; output is null and Exception occured with message "Enumeration yielded no results". why? how i can fix it? public IQueryable<SearchResult> PerformSearch(string query, int skip = 0, int take = 5) { if (!string.IsNullOrEmpty(query)) { var queryList = query.Split('+').ToList(); var results = GENERATERESULTS(); string key; foreach (string _q in queryList) { if (_q.StartsWith("(") && _q.EndsWith(")")) { key = _q.Replace("(", "").Replace(")", ""); results = results.Where(q => q.Title.Contains(key, StringComparison.CurrentCultureIgnoreCase)); } else if (_q.StartsWith("\"") && _q.EndsWith("\"")) { key = _q.Replace("\"", "").Replace("\"", ""); results = results.Where(q => q.Title.Contains(key, StringComparison.CurrentCulture)); } else if (_q.StartsWith("-(") && _q.EndsWith(")")) { key = _q.Replace("-(", "").Replace(")", ""); results = results.Where(q=> !q.Title.Contains(key, StringComparison.CurrentCultureIgnoreCase)); } else { key = _q; results = results.Where(q => q.Title.Contains(key, StringComparison.CurrentCulture)); } } this._Count = results.Count(); results = results.Skip(skip).Take(take); this._EndOn = DateTime.Now; this.ExecutionTime(); return results; } else return null; } thanks in advance ;)

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  • In mysql, is "explain ..." always safe?

    - by tye
    If I allow a group of users to submit "explain $whatever" to mysql (via Perl's DBI using DBD::mysql), is there anything that a user could put into $whatever that would make any database changes, leak non-trivial information, or even cause significant database load? If so, how? I know that via "explain $whatever" one can figure out what tables / columns exist (you have to guess names, though) and roughly how many records are in a table or how many records have a particular value for an indexed field. I don't expect one to be able to get any information about the contents of unindexed fields. DBD::mysql should not allow multiple statements so I don't expect it to be possible to run any query (just explain one query). Even subqueries should not be executed, just explained. But I'm not a mysql expert and there are surely features of mysql that I'm not even aware of. In trying to come up with a query plan, might the optimizer actual execute an expression in order to come up with the value that an indexed field is going to be compared against? explain select * from atable where class = somefunction(...) where atable.class is indexed and not unique and class='unused' would find no records but class='common' would find a million records. Might 'explain' evaluate somefunction(...)? And then could somefunction(...) be written such that it modifies data?

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