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  • sql select from a large number of IDs

    - by Claudiu
    I have a table, Foo. I run a query on Foo to get the ids from a subset of Foo. I then want to run a more complicated set of queries, but only on those IDs. Is there an efficient way to do this? The best I can think of is creating a query such as: SELECT ... --complicated stuff WHERE ... --more stuff AND id IN (1, 2, 3, 9, 413, 4324, ..., 939393) That is, I construct a huge "IN" clause. Is this efficient? Is there a more efficient way of doing this, or is the only way to JOIN with the inital query that gets the IDs? If it helps, I'm using SQLObject to connect to a PostgreSQL database, and I have access to the cursor that executed the query to get all the IDs.

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  • Multiple dependent select boxes, the Rails way?

    - by Adam Carlile
    Hey Guys I am trying to create a car application, each car belongs to a make and model, but only certain makes have certain models. So I would like a series of select boxes that are populated dynamically based on the previous, however I also would like to add another record to that select box if you cant find the one you want. I would just like to know your thoughts on how to accomplish this in a rails way? Cheers Adam

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  • select multiple columns using linq and sum them up

    - by Yustme
    Hi, How can i select multiple columns and calculate the total amount. For example, in my database i got a few fields which are named: 5hunderedBills, 2hunderedBills, 1hunderedBills, etc. And the value of those fields are for example: 5, 2, 3 And the sum would be: 5hunderedBills * 5 + 2hunderedBills * 2 + 1hunderedBills * 3 How can i do that with LINQ in one select statement?

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  • Is my understanding of "select distinct" correct?

    - by paxdiablo
    We recently discovered a performance problem with one of our systems and I think I have the fix but I'm not certain my understanding is correct. In simplest form, we have a table blah into which we accumulate various values based on a key field. The basic form is: recdate date rectime time system varchar(20) count integer accum1 integer accum2 integer There are a lot more accumulators than that but they're all of the same form. The primary key is made up of recdate, rectime and system. As values are collected to the table, the count for a given recdate/rectime/system is incremented and the values for that key are added to the accumulators. That means the averages can be obtained by using accumN / count. Now we also have a view over that table specified as follows: create view blah_v ( recdate, rectime, system, count, accum1, accum2 ) as select distinct recdate, rectime, system, count, value (case when count > 0 then accum1 / count end, 0), value (case when count > 0 then accum2 / count end, 0) from blah; In other words, the view gives us the average value of the accumulators rather than the sums. It also makes sure we don't get a divide-by-zero in those cases where the count is zero (these records do exist and we are not allowed to remove them so don't bother telling me they're rubbish - you're preaching to the choir). We've noticed that the time difference between doing: select distinct recdate from XX varies greatly depending on whether we use the table or the view. I'm talking about the difference being 1 second for the table and 27 seconds for the view (with 100K rows). We actually tracked it back to the select distinct. What seems to be happening is that the DBMS is actually loading all the rows in and sorting them so as to remove duplicates. That's fair enough, it's what we stupidly told it to do. But I'm pretty sure the fact that the view includes every component of the primary key means that it's impossible to have duplicates anyway. We've validated the problem since, if we create another view without the distinct, it performs at the same speed as the underlying table. I just wanted to confirm my understanding that a select distinct can not have duplicates if it includes all the primary key components. If that's so, then we can simply change the view appropriately.

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  • Change event on <select>

    - by adivasile
    If i attach a change event listener on a<select> how do i acces the option that was selected (not just the value, the actual element). $('select').addEvent('change',function(event) { //?? }); Note: i'm using Mootools

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  • CSS - changing the font color for a from select option in firefox

    - by Mick
    I'm building a website for my church, and I'm teaching myself all about web design along the way. http://www.wilmingtonchurchofgod.org/contact_us.html is the link where you can see my issue. If you look at that page in firefox, and you click the select part of the form (next to, "Who would you like to contact?") you will see that when you hover over a choice, the font is white. I have tried various things to fix this, but can't find a solution. This seems to be specific to Firefox. Here is the relevant CSS. input, textarea, select, option{ padding: 6px; border: solid 1px #E5E5E5; outline: 0; font: normal 13px/100% Verdana, Tahoma, sans-serif; width: 200px; background: #FFFFFF url(images/from-grad.jpg) left top repeat-x; background: -webkit-gradient(linear, left top, left 25, from(#FFFFFF), color-stop(4%, #EEEEEE), to(#FFFFFF)); background: -moz-linear-gradient(top, #FFFFFF, #EEEEEE 1px, #FFFFFF 25px); box-shadow: rgba(0,0,0, 0.15) 0px 0px 8px; -moz-box-shadow: rgba(0,0,0, 0.15) 0px 0px 8px; -webkit-box-shadow: rgba(0,0,0, 0.15) 0px 0px 8px; } option{ padding:0px; } textarea { width: 400px; max-width: 400px; height: 150px; line-height: 150%; } input:hover, textarea:hover, input:focus, textarea:focus{ border-color: #C9C9C9; -webkit-box-shadow: rgba(0, 0, 0, 0.15) 0px 0px 8px; -moz-box-shadow: rgba(0,0,0, 0.15) 0px 0px 8px; } option:hover, option:focus, select:hover, select:focus { color: black; border-color: #C9C9C9; -webkit-box-shadow: rgba(0, 0, 0, 0.15) 0px 0px 8px; -moz-box-shadow: rgba(0,0,0, 0.15) 0px 0px 8px; } Another side note is that I can't get any background gradient at all to show up on Google Chome (yet it does on Safari and they are supposed to use the same kit?) Any help with these two things would be greatly appreciated.

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  • Select back things that _don't_ exist

    - by bobobobo
    I have this table. I want to select back the items that don't exist already, so I can create them. table tags +---------+-------+ | tagId | name | | 1 | C | | 2 | DX | | 3 | CG | Say SQL looks like: select name from tags where name in ( 'C', 'CG', 'RX' ) You get back 'C' and 'CG', so you know you have to create 'RX'. Is there a way to get a MySQL statement like this to return 'RX' instead, when 'RX' doesn't already exist?

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  • C# Select clause returns system exception instead of relevant object

    - by Kashif
    I am trying to use the select clause to pick out an object which matches a specified name field from a database query as follows: objectQuery = from obj in objectList where obj.Equals(objectName) select obj; In the results view of my query, I get: base {System.SystemException} = {"Boolean Equals(System.Object)"} Where I should be expecting something like a Car, Make, or Model Would someone please explain what I am doing wrong here? The method in question can be seen here: // this function searches the database's table for a single object that matches the 'Name' property with 'objectName' public static T Read<T>(string objectName) where T : IEquatable<T> { using (ISession session = NHibernateHelper.OpenSession()) { IQueryable<T> objectList = session.Query<T>(); // pull (query) all the objects from the table in the database int count = objectList.Count(); // return the number of objects in the table // alternative: int count = makeList.Count<T>(); IQueryable<T> objectQuery = null; // create a reference for our queryable list of objects T foundObject = default(T); // create an object reference for our found object if (count > 0) { // give me all objects that have a name that matches 'objectName' and store them in 'objectQuery' objectQuery = from obj in objectList where obj.Equals(objectName) select obj; // make sure that 'objectQuery' has only one object in it try { foundObject = (T)objectQuery.Single(); } catch { return default(T); } // output some information to the console (output screen) Console.WriteLine("Read Make: " + foundObject.ToString()); } // pass the reference of the found object on to whoever asked for it return foundObject; } } Note that I am using the interface "IQuatable<T>" in my method descriptor. An example of the classes I am trying to pull from the database is: public class Make: IEquatable<Make> { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual IList<Model> Models { get; set; } public Make() { // this public no-argument constructor is required for NHibernate } public Make(string makeName) { this.Name = makeName; } public override string ToString() { return Name; } // Implementation of IEquatable<T> interface public virtual bool Equals(Make make) { if (this.Id == make.Id) { return true; } else { return false; } } // Implementation of IEquatable<T> interface public virtual bool Equals(String name) { if (this.Name.Equals(name)) { return true; } else { return false; } } } And the interface is described simply as: public interface IEquatable<T> { bool Equals(T obj); }

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  • select redirection

    - by Lormitto
    Hi, While considering another problem one question appeared. I do not know how to write html when I want to redirect page when select option changes. In other words user chooses option from select list and page is redirected after that. Have you met anything like this? Regards,

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  • exiting from a blocking select call!

    - by Jay
    I am calling a third party API which creates a socket, does a connect and then calls select API by passing the socket to block forever. I don't have access to the socket. Is there some way in which I can make the select call come out from my application without having access to the socket? My platform is Windows.

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  • How to display MySQL Select statement results in PHP

    - by Vafello
    I have the following code and it should return just one value (id) from mysql table. The following code doesnt work. How can I output it without creating arrays and all this stuff, just a simple output of one value. $query = "SELECT id FROM users_entity WHERE username = 'Admin' "; $result = map_query($query); echo $result;

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  • MYSQL JOIN SELECT Statment - omit duplicated

    - by mouthpiec
    Hi, I am tying to join the following 2 queries but I am having duplicated .... it is possible to remove duplacted fro this: ( SELECT bar_id, bar_name, town_name, bar_telephone, (subscription_type_id *2) AS subscription_type_id FROM bar, sportactivitybar, towns, subscriptiontype WHERE sport_activity_id_fk =14 AND bar_id = bar_id_fk AND town_id = town_id_fk AND subscription_type_id = subscription_type_id_fk ) UNION ( SELECT bar_id, bar_name, town_name, bar_telephone, subscription_type_id FROM bar, towns, subscriptiontype WHERE town_id = town_id_fk AND subscription_type_id = subscription_type_id_fk ) ORDER BY subscription_type_id DESC , RAND( ) Please note that I need to omit those duplicates that will have a lower subscription_type_id

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  • HTML Select, force direction down.

    - by Kyle Sevenoaks
    Is there a way to force the dropdown direction of a select element in HTML down? At the moment we have a product display page, the select box appears below the halfway mark of the screen in a widescreen resolution and therefore makes the dropdown go up. Is this possible? Thanks.

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  • Datable.Select sort expression

    - by xyz
    Hi, I have datatable with column name tag and 100 rows of data.I need to filter this table with tag starting with "UNKNOWN". What should my sortexpression for datatable.select be ? I'm trying the following. Datarow[] abc = null; abc = dtTagList.Select(string.format("tag='{0}'","UNKNOWN")) How can I achieve tag startswith 'UNKNOWN' in the above code ?

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  • Select where and where not

    - by Simon
    I have a table containing lessons that I called "cours" (french) and I have several cours inside and I have linked them to students with a table between them to see if they go to the lessons or not. I would like to return data with the SELECT and the data that are NOT select. So, If one student follow 3 courses of 5, I would like to return the 3 courses that he follow and the 2 courses that he doesn't follow. Is there a way to do it ?

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  • insert ... select with divide operator in select errors?

    - by Mark
    Hi, the following query CREATE TABLE IF NOT EXISTS XY ( x INT NOT NULL , y FLOAT NULL , PRIMARY KEY(x) ) INSERT INTO XY (x,y) (select 1 as x ,(1/7) as y); errors with Error code 1064, SQL state 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'INSERT INTO XY (x,y) (select 1 as x ,(1/7) as y)' at line 7 Line 1, column 1 any ideas?

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  • Better mode for do a select with group by

    - by Luca Romagnoli
    Hi i've wrote a query that works: SELECT `comments`.* FROM `comments` RIGHT JOIN (SELECT MAX( id ) AS id, core_id, topic_id FROM comments GROUP BY core_id, topic_id order by id desc) comm ON comm.id = comments.id LIMIT 10 I want know if is possible and how rewrite it for get better performance. thanks

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