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  • How to query range of data in DB2 with highest performance?

    - by Fuangwith S.
    Usually, I need to retrieve data from a table in some range; for example, a separate page for each search result. In MySQL I use LIMIT keyword but in DB2 I don't know. Now I use this query for retrieve range of data. SELECT * FROM( SELECT SMALLINT(RANK() OVER(ORDER BY NAME DESC)) AS RUNNING_NO , DATA_KEY_VALUE , SHOW_PRIORITY FROM EMPLOYEE WHERE NAME LIKE 'DEL%' ORDER BY NAME DESC FETCH FIRST 20 ROWS ONLY ) AS TMP ORDER BY TMP.RUNNING_NO ASC FETCH FIRST 10 ROWS ONLY but I know it's bad style. So, how to query for highest performance?

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  • How can I kill MySQL queries every 60 seconds in Windows?

    - by Ethan Allen
    I want to check my MySQL server every minute and kill queries that have run longer than 150 seconds. The main reason I want to do this is because I don't want queries from certain people to lock up the DB for everyone else. I know this is not the ultimate solution to the problem, but at least it's a fallback in case something goes wrong with a query. I don't have a slave DB (this is just an at-home project). I'd like to schedule a script to run that does this for me. I'm unfamiliar with Perl or Ruby and I need it done on my Windows 2008 Server box. I've looked into creating a simple cmd line script, but that doesn't seem to be possible. I know currently I can do something like this but I have to do it manually: mysqladmin processlist mysqladmin kill Anyone have any ideas or examples on how I could do this?

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  • Determine caller within stored proc or trigger

    - by Mike Clark
    I am working with an insert trigger within a Sybase database. I know I can access the @@nestlevel to determine whether I am being called directly or as a result of another trigger or procedure. Is there any way to determine, when the nesting level is deeper than 1, who performed the action causing the trigger to fire? For example, was the table inserted to directly, was it inserted into by another trigger and if so, which one.

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  • Update with inner join ?

    - by phenevo
    I have two databases: DB1 and DB2 How to do something like: update myServer.DB1.dbo.hotels.Name = myServer.DB2.dbo.hotels.Name join myServer.DB2.dbo.hotels on myServer.DB2.dbo.hotels.Code= myServer.DB1.dbo.hotels.Code where myServer.DB2.dbo.hotels.CountryCoe != myServer.DB1.dbo.hotels.CountryCode

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  • Select rows in random order and then reverse it

    - by Faruz
    I need to select rows in random order and return a query which holds the rows in both regular order and in reverse order. This is done to simulate a fantasy draft for a basketball game I'm working on. For example, I need a result set as followed: team1 1 team2 2 team6 3 team9 4 team9 5 team6 6 team2 7 team1 8 As you can see, the first four teams are random then then following four are in reverse order. Hope I managed to explain the problem, if not - please comment and I'll explain further.

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  • Multiple Foriegn Keys from One Table linking to single Primary Key in second Table

    - by croker10
    Hi all, I have a database with three tables, a household table, an adults table and a users table. The Household table contains two foreign keys, iAdult1ID and iAdult2ID. The Users table has a iUserID primary key and the Adult table has a corresponding iUserID foreign key. One of the columns in the Users table is strUsername, an e-mail address. I am trying to write a query that will allow me to search for an e-mail address for either adult that has a relation to the household. So I have two questions, assuming that all the values are not null, how can I do this? And two, in reality, iAdult2ID can be null, is it still possible to write a query to do this? Thanks for your help. Let me know if you need any more information.

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  • Why can't you return a List from a Compiled Query?

    - by Andrew
    I was speeding up my app by using compiled queries for queries which were getting hit over and over. I tried to implement it like this: Function Select(ByVal fk_id As Integer) As List(SomeEntity) Using db As New DataContext() db.ObjectTrackingEnabled = False Return CompiledSelect(db, fk_id) End Using End Function Shared CompiledSelect As Func(Of DataContext, Integer, List(Of SomeEntity)) = _ CompiledQuery.Compile(Function(db As DataContext, fk_id As Integer) _ (From u In db.SomeEntities _ Where u.SomeLinkedEntity.ID = fk_id _ Select u).ToList()) This did not work and I got this error message: Type : System.ArgumentNullException, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 Message : Value cannot be null. Parameter name: value However, when I changed my compiled query to return IQueryable instead of List like so: Function Select(ByVal fk_id As Integer) As List(SomeEntity) Using db As New DataContext() db.ObjectTrackingEnabled = False Return CompiledSelect(db, fk_id).ToList() End Using End Function Shared CompiledSelect As Func(Of DataContext, Integer, IQueryable(Of SomeEntity)) = _ CompiledQuery.Compile(Function(db As DataContext, fk_id As Integer) _ From u In db.SomeEntities _ Where u.SomeLinkedEntity.ID = fk_id _ Select u) It worked fine. Can anyone shed any light as to why this is? BTW, compiled queries rock! They sped up my app by a factor of 2.

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  • Strange behavior with large Object Types

    - by Peter Lang
    I recognized that calling a method on an Oracle Object Type takes longer when the instance gets bigger. The code below just adds rows to a collection stored in the Object Type and calls the empty dummy-procedure in the loop. Calls are taking longer when more rows are in the collection. When I just remove the call to dummy, performance is much better (the collection still contains the same number of records): Calling dummy: Not calling dummy: 11 0 81 0 158 0 Code to reproduce: Create Type t_tab Is Table Of VARCHAR2(10000); Create Type test_type As Object( tab t_tab, Member Procedure dummy ); Create Type Body test_type As Member Procedure dummy As Begin Null; --# Do nothing End dummy; End; Declare v_test_type test_type := New test_type( New t_tab() ); Procedure run_test As start_time NUMBER := dbms_utility.get_time; Begin For i In 1 .. 200 Loop v_test_Type.tab.Extend; v_test_Type.tab(v_test_Type.tab.Last) := Lpad(' ', 10000); v_test_Type.dummy(); --# Removed this line in second test End Loop; dbms_output.put_line( dbms_utility.get_time - start_time ); End run_test; Begin run_test; run_test; run_test; End; I tried with both 10g and 11g. Can anyone explain/reproduce this behavior?

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  • Having different database sorting order (default_scope) for two different views

    - by Juniper747
    In my model (pins.rb), I have two sorting orders: default_scope order: 'pins.featured DESC' #for adding featured posts to the top of a list default_scope order: 'pins.created_at DESC' #for adding the remaining posts beneath the featured posts This sorting order (above) is how I want my 'pins view' (index.html.erb) to look. Which is just a list of ALL user posts. In my 'users view' (show.html.erb) I am using the same model (pins.rb) to list only current_user pins. HOWEVER, I want to sorting order to ignore the "featured" default scope and only use the second scope: default_scope order: 'pins.created_at DESC' How can I accomplish this? I tried doing something like this: default_scope order: 'pins.featured DESC', only: :index default_scope order: 'pins.created_at DESC' But that didn't fly... UPDATE I updated my model to define a scope: scope :featy, order: 'pins.featured DESC' default_scope order: 'pins.created_at DESC' And updated my pins view to: <%= render @pins.featy %> However, now when I open my pins view, I get the error: undefined method `featy' for #<Array:0x00000100ddbc78> UPDATE 2 User.rb class User < ActiveRecord::Base attr_accessible :name, :email, :username, :password, :password_confirmation, :avatar, :password_reset_token, :password_reset_sent_at has_secure_password has_many :pins, dependent: :destroy #destroys user posts when user is destroyed # has_many :featured_pins, order: 'featured DESC', class_name: "Pin", source: :pin has_attached_file :avatar, :styles => { :medium => "300x300#", :thumb => "120x120#" } before_save { |user| user.email = user.email.downcase } before_save { |user| user.username = user.username.downcase } before_save :create_remember_token before_save :capitalize_name validates :name, presence: true, length: { maximum: 50 } VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i VALID_USERNAME_REGEX = /^[A-Za-z0-9]+(?:[_][A-Za-z0-9]+)*$/ validates :email, presence: true, format: { with: VALID_EMAIL_REGEX }, uniqueness: { case_sensitive: false } validates :username, presence: true, format: { with: VALID_USERNAME_REGEX }, uniqueness: { case_sensitive: false } validates :password, length: { minimum: 6 }, on: :create #on create, because was causing erros on pw_reset Pin.rb class Pin < ActiveRecord::Base attr_accessible :content, :title, :privacy, :date, :dark, :bright, :fragmented, :hashtag, :emotion, :user_id, :imagesource, :imageowner, :featured belongs_to :user before_save :capitalize_title before_validation :generate_slug validates :content, presence: true, length: { maximum: 8000 } validates :title, presence: true, length: { maximum: 24 } validates :imagesource, presence: { message: "Please search and choose an image" }, length: { maximum: 255 } validates_inclusion_of :privacy, :in => [true, false] validates :slug, uniqueness: true, presence: true, exclusion: {in: %w[signup signin signout home info privacy]} # for sorting featured and newest posts first default_scope order: 'pins.created_at DESC' scope :featured_order, order: 'pins.featured DESC' def to_param slug # or "#{id}-#{name}".parameterize end def generate_slug # makes the url slug address bar freindly self.slug ||= loop do random_token = Digest::MD5.hexdigest(Time.zone.now.to_s + title)[0..9]+"-"+"#{title}".parameterize break random_token unless Pin.where(slug: random_token).exists? end end protected def capitalize_title self.title = title.split.map(&:capitalize).join(' ') end end users_controller.rb class UsersController < ApplicationController before_filter :signed_in_user, only: [:edit, :update, :show] before_filter :correct_user, only: [:edit, :update, :show] before_filter :admin_user, only: :destroy def index if !current_user.admin? redirect_to root_path end end def menu @user = current_user end def show @user = User.find(params[:id]) @pins = @user.pins current_user.touch(:last_log_in) #sets the last log in time if [email protected]? render 'pages/info/' end end def new @user = User.new end pins_controller.rb class PinsController < ApplicationController before_filter :signed_in_user, except: [:show] # GET /pins, GET /pins.json def index #Live Feed @pins = Pin.all @featured_pins = Pin.featured_order respond_to do |format| format.html # index.html.erb format.json { render json: @pins } end end # GET /pins, GET /pins.json def show #single Pin View @pin = Pin.find_by_slug!(params[:id]) require 'uri' #this gets the photo's id from the stored uri @image_id = URI(@pin.imagesource).path.split('/').second if @pin.privacy == true #check for private pins if signed_in? if @pin.user_id == current_user.id respond_to do |format| format.html # show.html.erb format.json { render json: @pin } end else redirect_to home_path, notice: "Prohibited 1" end else redirect_to home_path, notice: "Prohibited 2" end else respond_to do |format| format.html # show.html.erb format.json { render json: @pin } end end end # GET /pins, GET /pins.json def new @pin = current_user.pins.new respond_to do |format| format.html # new.html.erb format.json { render json: @pin } end end # GET /pins/1/edit def edit @pin = current_user.pins.find_by_slug!(params[:id]) end Finally, on my index.html.erb I have: <%= render @featured_pins %>

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  • Syntax error in INSERT INTO statement

    - by user454563
    I wrote a program that connects to MS Access. When I fill in the fields and add a new item to Access the program fails. The exception is "Syntax error in INSERT INTO statement" Here is the relevant code. **************************************************************** AdoHelper.cs **************************************************************** using System; using System.Collections.Generic; using System.Text; using System.Data; using System.Data.OleDb; namespace Yad2 { class AdoHelper { //get the connection string from the app.config file //Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\Yad2.accdb static string connectionString = Properties.Settings.Default.DBConnection.ToString(); //declare the db connection static OleDbConnection con = new OleDbConnection(connectionString); /// <summary> /// To Execute queries which returns result set (table / relation) /// </summary> /// <param name="query">the query string</param> /// <returns></returns> public static DataTable ExecuteDataTable(string query) { try { con.Open(); OleDbCommand command = new OleDbCommand(query, con); System.Data.OleDb.OleDbDataAdapter tableAdapter = new System.Data.OleDb.OleDbDataAdapter(command); DataTable dt = new DataTable(); tableAdapter.Fill(dt); return dt; } catch (Exception ex) { throw ex; } finally { con.Close(); } } /// <summary> /// To Execute update / insert / delete queries /// </summary> /// <param name="query">the query string</param> public static void ExecuteNonQuery(string query) { try { con.Open(); System.Data.OleDb.OleDbCommand command = new System.Data.OleDb.OleDbCommand(query, con); command.ExecuteNonQuery(); } catch (Exception ex) { throw ex; } finally { con.Close(); } } /// <summary> /// To Execute queries which return scalar value /// </summary> /// <param name="query">the query string</param> public static object ExecuteScalar(string query) { try { con.Open(); System.Data.OleDb.OleDbCommand command = new System.Data.OleDb.OleDbCommand(query, con); /// here is the Excaption !!!!!!!!! return command.ExecuteScalar(); } catch { throw; } finally { con.Close(); } } } } **************************************************************************** **************************************************************************** DataQueries.cs **************************************************************************** using System; using System.Collections.Generic; using System.Text; using System.Data; namespace Yad2 { class DataQueries { public static DataTable GetAllItems() { try { string query = "Select * from Messages"; DataTable dt = AdoHelper.ExecuteDataTable(query); return dt; } catch (Exception ex) { throw ex; } } public static void AddNewItem(string mesNumber, string title , string mesDate , string contactMail , string mesType , string Details ) { string query = "Insert into Messages values(" + mesNumber + " , '" + title + "' , '" + mesDate + "' , '" + contactMail + "' , , '" + mesType + "' , '" + Details + "')"; AdoHelper.ExecuteNonQuery(query); } public static void DeleteDept(int mesNumber) { string query = "Delete from Item where MessageNumber=" + mesNumber; AdoHelper.ExecuteNonQuery(query); } } } *********************************************************************************************** plase help me .... why the program falls ?

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  • How to write contents of a rails database to external file

    - by user1296787
    I'm trying to have rails send the contents of my database to an external textfile. I wanted this done everytime a new user is created. However, when i try to do the following in my user.rb model file, before_save :write_data def write_data() File.open("data.txt", "w") do |myfile| myfile.write(User.all) end end It doesn't write the actual contents of the database, instead, it displays something like this User:0x109858540 Can anyone help? Thanks.

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  • Can I have a CASE statement within a WHILE loop?

    - by John
    This is what I'm doing: while (@counter < 3 and @newBalance >0) begin CASE when @counter = 1 then ( @monFee1 = @monthlyFee, @newBalance = @newBalance-@fee) when @counter = 2 then ( @monFee2 = @monthlyFee, @newBalance = @newBalance-@fee) END @counter = @counter +1 end I get this error: Incorrect syntax near the keyword 'CASE'. No idea why. Please help!

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  • making a combined sum of two columns

    - by bsandrabr
    I have a table (apples) containing: cid date_am date_pm ---------------------- 1 1 1 2 2 1 3 1 3 1 1 2 I asked a question earlier (badly) about how I would rank the customers in order of the number of ones(1) they had. The solution was (based on one column): SELECT cid, sum( date_pm ) AS No_of_ones FROM apples WHERE date_am =1 GROUP BY cid ORDER BY no_of_ones DESC This works great for one column but how would I do the same for the sum of the two columns. ie. SELECT cid, sum( date_pm ) AS No_of_ones FROM apples WHERE date_am =1 add to SELECT cid, sum( date_am ) AS No_of_ones FROM apples WHERE date_pm =1 GROUP by cid ORDER by no_of_ones(added) hope I've managed to make that clear enough for you to help -thanks

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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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  • Best way to run multiple queries per second on database, performance wise?

    - by Michael Joell
    I am currently using Java to insert and update data multiple times per second. Never having used databases with Java, I am not sure what is required, and how to get the best performance. I currently have a method for each type of query I need to do (for example, update a row in a database). I also have a method to create the database connection. Below is my simplified code. public static void addOneForUserInChannel(String channel, String username) throws SQLException { Connection dbConnection = null; PreparedStatement ps = null; String updateSQL = "UPDATE " + channel + "_count SET messages = messages + 1 WHERE username = ?"; try { dbConnection = getDBConnection(); ps = dbConnection.prepareStatement(updateSQL); ps.setString(1, username); ps.executeUpdate(); } catch(SQLException e) { System.out.println(e.getMessage()); } finally { if(ps != null) { ps.close(); } if(dbConnection != null) { dbConnection.close(); } } } And my DB connection private static Connection getDBConnection() { Connection dbConnection = null; try { Class.forName(DB_DRIVER); } catch (ClassNotFoundException e) { System.out.println(e.getMessage()); } try { dbConnection = DriverManager.getConnection(DB_CONNECTION, DB_USER,DB_PASSWORD); return dbConnection; } catch (SQLException e) { System.out.println(e.getMessage()); } return dbConnection; } This seems to be working fine for now, with about 1-2 queries per second, but I am worried that once I expand and it is running many more, I might have some issues. My questions: Is there a way to have a persistent database connection throughout the entire run time of the process? If so, should I do this? Are there any other optimizations that I should do to help with performance? Thanks

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  • Can't create a MySQL query that generates 4 rows for each row in the table it references.

    - by UkraineTrain
    I need to create a MySQL query that generates 4 rows for each row in the table it references. I need some of the information in those rows to repeat and some to be different. In the table each row stands for one day. I need to break the day up in 6 hour increments, hence the four rows for each entry. I need to create one column which for each day will have '12AM', '6AM', '12PM', and '6PM' values and another column will have the corresponding numeric values calculated for those entries. Thanks a lot in advance and I will really appreciate any help on this.

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  • Why would using a Temp table be faster than a nested query?

    - by Mongus Pong
    We are trying to optimise some of our queries. One query is doing the following: SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, INTO [#Gadget] FROM task t SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) as Client FROM [#Gadget] order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC DROP TABLE [#Gadget] (I have removed the complex subquery, cos I dont think its relevant other than to explain why this query has been done as a two stage process.) Now I would have thought it would be far more efficient to merge this down into a single query using subqueries as : SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) FROM ( SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, FROM task t ) as sub order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC This would give the optimiser better information to work out what was going on and avoid any temporary tables. It should be faster. But it turns out it is a lot slower. 8 seconds vs under 5 seconds. I cant work out why this would be the case as all my knowledge of databases imply that subqueries would always be faster than using temporary tables. Can anyone explain what could be going on!?!?

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  • How can I tell when a MySQL table was last updated?

    - by RaGE
    In the footer of my page, I would like to add something like "last updated the xx/xx/200x"; with this date being the last time a certain mySQL table has been updated. What is the best way to do that ? Is there a function to retrieve the date ? Should I make an access to the database everytime my footer is displayed ?

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  • VB.NET: SQLite to MSSQL

    - by user1736785
    I have a vb.net project that uses a SQLite database. I do this by using dataset/table adapters. The client is happy and all works well. However I have just heard that they plan on providing this product to another customer that wishes to use their MSSQL database. So I am writing this post so I can mentally prepare for this before I begin. I am not a database pro and have really enjoyed the simplicity of setting up and managing an SQLite database. So any ideas on the easiest way to support MSSQL as well? I am happy to run them parallel to each other. Can I just make a separate service / middleware that syncs the SQLite database to the MSSQL on a timer and does not care about what the main app is up to? Any pointers are appreciated.

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  • mySQL: Order by field size/length

    - by Sadi
    Here is a table structure (e.g. test): __________________________________________ | Field Name | Data Type | |________________|_________________________| | id | BIGINT (20) | |________________|_________________________| | title | varchar(25) | |________________|_________________________| | description | text | |________________|_________________________| A query like: SELECT * FROM TEST ORDER BY description; But I would like to order by the field size/length of the field description. The field type will be TEXT or BLOB.

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