Search Results

Search found 53054 results on 2123 pages for 'sql sample database'.

Page 918/2123 | < Previous Page | 914 915 916 917 918 919 920 921 922 923 924 925  | Next Page >

  • Has inheritance become bad?

    - by mafutrct
    Personally, I think inheritance is a great tool, that, when applied reasonably, can greatly simplify code. However, I seems to me that many modern tools dislike inheritance. Let's take a simple example: Serialize a class to XML. As soon as inheritance is involved, this can easily turn into a mess. Especially if you're trying to serialize a derived class using the base class serializer. Sure, we can work around that. Something like a KnownType attribute and stuff. Besides being an itch in your code that you have to remember to update every time you add a derived class, that fails, too, if you receive a class from outside your scope that was not known at compile time. (Okay, in some cases you can still work around that, for instance using the NetDataContract serializer in .NET. Surely a certain advancement.) In any case, the basic principle still exists: Serialization and inheritance don't mix well. Considering the huge list of programming strategies that became possible and even common in the past decade, I feel tempted to say that inheritance should be avoided in areas that relate to serialization (in particular remoting and databases). Does that make sense? Or am messing things up? How do you handle inheritance and serialization?

    Read the article

  • SqlCeCommand ExecuteNonQuery performance issue

    - by Michael
    I've been asked to resolve an issue with a .Net/SqlServerCe application. Specifically, after repeated inserts against the db, performance becomes increasingly degraded. In one instance at ~200 rows, in another at ~1000 rows. In the latter case the code being used looks like this: Dim cm1 As System.Data.SqlServerCe.SqlCeCommand = cn1.CreateCommand cm1.CommandText = "INSERT INTO Table1 Values(?,?,?,?,?,?,?,?,?,?,?,?,?)" For j = 0 To ds.Tables(0).Rows.Count - 1 'this is 3110 For i = 0 To 12 cm1.Parameters(tbl(i, 0)).Value = Vals(j,i) 'values taken from a different db Next cm1.ExecuteNonQuery() Next The specifics aren't super important (like what 'tbl' is, etc) but rather whether or not this code should be expected to handle this number of inserts, or if the crawl I'm witnessing is to be expected.

    Read the article

  • Question on different ways to link tables

    - by dotnetdev
    What is the difference between linking two tables and then the PK is an FK in the other table, but the FK has not got the primary key option (so it does not have the gold key), and having the PK in one table as a PK in another table? Am I right to think that the second option is for a many-to-many relationship? Thanks

    Read the article

  • custom sorting or ordering a table without resorting the whole shebang

    - by fuugus
    for ten years we've been using the same custom sorting on our tables, i'm wondering if there is another solution which involves fewer updates, especially since today we'd like to have a replication/publication date and would'nt like to have our replication replicate unnecessary entries. i had a look into nested sets, but it does'nt seem to do the job for us. base table: id | a_sort ---+------- 1 10 2 20 3 30 after inserting insert into table (a_sort) values(15) an entry at the second position. id | a_sort ---+------- 1 10 2 20 3 30 4 15 ordering the table with select * from table order by a_sort and resorting all the a_sort entries, updating at least id=(2,3,4) will of course produce the desired output id | a_sort ---+------- 1 10 4 20 2 30 3 40 the column names, the column count, datatypes, a possible join, possible triggers or the way the resorting is done is/are irrelevant to the problem. also we've found some pretty neat ways to do this task fast. only; how the heck can we reduce the updates in the db to 1 or 2 max. seems like an awfully common problem. the captain obvious in me thougth once "use an a_sort float(53), insert using a fixed value of ordervaluefirstentry+abs(ordervaluefirstentry-ordervaluenextentry)/2".. but this would only allow around 1040 "in between" entries - so never resorting seems a bit problematic ;)

    Read the article

  • How to combine two rows and calculate the time difference between two timestamp values in MySQL?

    - by Nadar
    I have a situation that I'm sure is quite common and it's really bothering me that I can't figure out how to do it or what to search for to find a relevant example/solution. I'm relatively new to MySQL (have been using MSSQL and PostgreSQL earlier) and every approach I can think of is blocked by some feature lacking in MySQL. I have a "log" table that simply lists many different events with their timestamp (stored as datetime type). There's lots of data and columns in the table not relevant to this problem, so lets say we have a simple table like this: CREATE TABLE log ( id INT NOT NULL AUTO_INCREMENT, name VARCHAR(16), ts DATETIME NOT NULL, eventtype VARCHAR(25), PRIMARY KEY (id) ) Let's say that some rows have an eventtype = 'start' and others have an eventtype = 'stop'. What I want to do is to somehow couple each "startrow" with each "stoprow" and find the time difference between the two (and then sum the durations per each name, but that's not where the problem lies). Each "start" event should have a corresponding "stop" event occuring at some stage later then the "start" event, but because of problems/bugs/crashed with the data collector it could be that some are missing. In that case I would like to disregard the event without a "partner". That means that given the data: foo, 2010-06-10 19:45, start foo, 2010-06-10 19:47, start foo, 2010-06-10 20:13, stop ..I would like to just disregard the 19:45 start event and not just get two result rows both using the 20:13 stop event as the stop time. I've tried to join the table with itself in different ways, but the key problems for me seems to be to find a way to correctly identify the corresponding "stop" event to the "start" event for the given "name". The problem is exactly the same as you would have if you had table with employees stamping in and out of work and wanted to find out how much they actually were at work. I'm sure there must be well known solutions to this, but I can't seem to find them...

    Read the article

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

    - by bread
    Does it make a difference if you do count(*) vs count(column-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(column-name): SELECT customerid, count(customerid), sum(price) FROM items_ordered GROUP BY customerid HAVING count(customerid) > 1;

    Read the article

  • select row from table and substitute a field with one from another column if not null

    - by EarthMind
    I'm trying construct a PostgreSQL query that does the following but so far my efforts have been in vain. Problem: There are two tables: A and B. I'd like to select all columns from table A (having columns: id, name, description) and substitute the "A.name" column with the value of the column "B.title" from table B (having columns: id, table_A_id title, langcode) where B.table_A_id is 5 and B.langcode is "nl" (if there are any rows). I've tried using a CASE and COALESCE() but failed due to my inexperience with both concepts. Thanks in advance.

    Read the article

  • select row from table and substitute a field with one from another column if it exists

    - by EarthMind
    I'm trying construct a PostgreSQL query that does the following but so far my efforts have been in vain. Problem: There are two tables: A and B. I'd like to select all columns from table A (having columns: id, name, description) and substitute the "A.name" column with the value of the column "B.title" from table B (having columns: id, table_A_id title, langcode) where B.table_A_id is 5 and B.langcode is "nl" (if there are any rows). My attempts: SELECT A.name, case when exists(select title from B where table_A_id = 5 and langcode= 'nl') then B.title else A.name END FROM A, B WHERE A.id = 5 and B.table_A_id = 5 and B.langcode = 'nl' -- second try: SELECT COALESCE(B.title, A.name) as name from A, B where A.id = 5 and B.table_A_id = 5 and exists(select title from B where table_A_id = 5 and langcode= 'nl') I've tried using a CASE and COALESCE() but failed due to my inexperience with both concepts. Thanks in advance.

    Read the article

  • query to return three records for each customer application based on the options declared in the pre

    - by kumarreddy
    tables look like this table1---customer application columns--- application id--primary key, name, ssn, ... ... table2----balance(actually its a view) columns--- amount balance, application id ...... ...... table3 ---- options columns--- optionid, option value(1,2,3,4), ...... ........ .... table4 ----- ratios columns--- ratios id, option value, ratio value, applicationid(have to think about it), ........ table 4(detail) option value, Ratios 1 ----- 30 1 ----- 40 1 ----- 30 2 ---- 100 2 ----- 0 2 ------ 0 3 ---- 60 3 ------ 30 3 ----- 10 4 ---- 50 4 ----- 30 4 ----- 20 as is the case...now i need to get three records for each customer application with varying balances in proportion of ratios declared in table 4 corresponding to option values...... plz let me know where i was unclear about returning records thanks in advance

    Read the article

  • is it possible to combine will_paginate with find_by_sql?

    - by Tam
    In my rails application I want to use will_paginate plugin to paginate on my query. Is that possible? I tried doing something like this but it didn't work: @users = User.find_by_sql(" SELECT u.id, u.first_name, u.last_name, CASE WHEN r.user_accepted =1 AND (r.friend_accepted =0 || r.friend_accepted IS NULL) .........").paginate( :page => @page, :per_page => @per_page, :conditions => conditions_hash, :order => 'first_name ASC') If not, can you recommend a way around this or a way that might work as I don't want to write my own pagination.

    Read the article

  • access: control source of textbox

    - by I__
    there is a form where a user enters a date in [Text4] when users clicks OK, the following code is run: DoCmd.OpenReport "All_Ones", acViewPreview the following is the control source of a textbox on the report [Forms]![By Number]![Text4] for some reason after the report is open, it just sayd #?nameor something like that, meaning that it is an invalid parameter. what am i doing wrong?

    Read the article

  • What is the best way to restore(rollback) data in an application to a specified state(date) ?

    - by panzerschreck
    Hello, An example would set the context right, the example below captures the various states of the entity, which needs to be reverted(rolled back) . State 1 - Recorded on 01-Mar-2010 Column1 Column2 Data1 0.56 State 2 - Recorded on 02-Mar-2010 Column1 Column2 Data1 0.57 State 3 - Recorded on 03-Mar-2010 Column1 Column2 Data1 0.58 User notices that state3 is not what he intended to be in, decides to revert back to state2. One approach that I can think of, without modifying the entity is via "auditing" all the inserts/updates, as below, the rollback information captures the data just before the updates/modifications on the entity, so that it can be applied in an order when you need to revert.Please note that changing the entity's schema, is not an option. Rollback - R1 recorded on 01-Mar-2010 Column1 Column2 Data1 0.56 Rollback - R2 Recorded on 02-Mar-2010 Column1 Column2 Data1 0.56 Rollback - R3 Recorded on 03-Mar-2010 Column1 Column2 Data1 0.57 So, to get to state2 , we would start with rollback information R1,apply R2 onto it. Is there a better approach to achieve this ? Thanks for your time.

    Read the article

  • What is the current status on Microsoft ProClarity?

    - by Ali_Abadani
    I don't really know how to compose this question. My complay has been using Microsoft ProClarity for few years and we have a quite a few users using it publising books and doing ad-hoc analysis. With the new Microsoft BI solutions, it seems like they are completely going away from ProClarity and replacing the OLAP analysis with Excel. I understand the with SharePoint and integration with PerformancePoint and reporting services the dashboards and reports would be done in SharePoint but what about the analysis? Any ideas?

    Read the article

  • How to differenciate two tables

    - by Nemat
    Hi friends.... I have two tables.I want to get all records from one table that are different from the records in second table. For eg. if we have four records in first table like A,B,C,D and three records in second table thats A,B,C then the answer of query should be D. I have tried "EXCEPT" operator but it doesnt work fine.Kindly help me in writing correct query for the given problem. Any help is appreciated.... Thanks in Advance Nemat

    Read the article

  • Help with query in Microsoft Access

    - by Gold
    I have 2 tables: Table A: code | name Table B: barcode | name Table B has full barcode and name, Table A has only code. I need to run update query that fill name in Table A. I tried something like: update A set name = (select top 1 Name from B where B.Code = mid(A.Barcode,1,8)) but it doesn't work.

    Read the article

  • PHP timeslot booking*

    - by boyee007
    regarding of this question.. PHP Booking timeslot I tried 'GROUP BY' id_timeslot still didnt work, as its only showing the booked timeslot not available i tried that solution, but give me an error and not quite understand how to use 'coelence' table timeslot (id_timeslot integer); table doctor (id_doctor integer); table bookslot (id_bookslot, id_doctor, id_timeslot integer); insert into doctor (id_doctor) values (1 = doc_A), (2 = doc_B), (3 = doc_C); insert into TimeSlot (id_timeslot) values (1 = 10:00:00), (2 = 10:15:00), (3 = 10:30:00), (4 = 10:45:00); insert into bookslot (id_doctor,id_timeslot) values (1,1), (1,5), (2,1), (2,4), (3,1); Join mysql table $q = $mysqli->query("SELECT * FROM bookslot RIGHT JOIN timeslot ON bookslot.id_timeslot = timeslot.id_timeslot LEFT JOIN doctor ON bookslot.id_doctor = doctor.id_doctor "); echoing result and checking if it matches todays date or else set available while($r = $q->fetch_array(MYSQLI_ASSOC)) : echo '<tr>'; echo '<td align="center">' . $r['times'] . '</td>'; if($r['booked_date'] == date('Y-m-d') && $r['id_doctor'] == 1): echo '<td><a href="#available" class="booked">booked</a></td>'; else : echo '<td><a href="#" class="available">available</a></td>'; endif; if($r['booked_date'] == date('Y-m-d') && $r['id_doctor'] == 2): echo '<td><a href="#available" class="booked">booked</a></td>'; else : echo '<td><a href="#" class="available">available</a></td>'; endif; if($r['booked_date'] == date('Y-m-d') && $r['id_doctor'] == 3): echo '<td><a href="#available" class="booked">booked</a></td>'; else : echo '<td><a href="#" class="available">available</a></td>'; endif; echo '</tr>'; endwhile; result from webpage and i want the result look like: id_timeslot doc_A doc_B doc_C ---------------------------------------------- 1 booked booked booked 2 available available available 3 available available available 4 available booked available 5 booked available available Any other solution please!

    Read the article

< Previous Page | 914 915 916 917 918 919 920 921 922 923 924 925  | Next Page >