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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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  • Adding Information in SQLite

    - by Cam
    Hi All, I am having trouble with my Android App when adding information into SQLite. I am relatively new to Java/SQLite and though I have followed a lot of tutorials on SQLite and have been able to get the example code to run I am unable to get tables to be created and data to import when running my own app. I have included my code in two Java files Questions (Main Program) and QuestionData (helper class represents the database). Questions.java: public class Questions extends Activity { private QuestionData questions; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.quiztest); questions = new QuestionData(this); try { Cursor cursor = getQuestions(); showQuestions(cursor); } finally { questions.close(); } } private Cursor getQuestions() { //Select Query String loadQuestions = "SELECT * FROM questionlist"; SQLiteDatabase db = questions.getReadableDatabase(); Cursor cursor = db.rawQuery(loadQuestions, null); startManagingCursor(cursor); return cursor; } private void showQuestions(Cursor cursor) { // Collect String Values from Query and Display them this part of the code is wokring fine when there is data present. QuestionData.java public class QuestionData extends SQLiteOpenHelper { private static final String DATABASE_NAME = "TriviaQuiz.db" ; private static final int DATABASE_VERSION = 2; public QuestionData(Context ctx) { super(ctx, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL("CREATE TABLE questionlist (_id INTEGER PRIMARY KEY AUTOINCREMENT, QID TEXT, QQuestion TEXT, QAnswer TEXT, QOption1 TEXT, QOption2 TEXT, QOption3 TEXT, QCategoryTagLvl1 TEXT, QCategoryTagLvl2 TEXT, QOptionalTag1 TEXT, QOptionalTag2 TEXT, QOptionalTag3 TEXT, QOptionalTag4 TEXT, QOptionalTag5 TEXT, QTimePeriod TEXT, QDifficultyRating TEXT, QGenderBias TEXT, QAgeBias TEXT, QRegion TEXT, QWikiLink TEXT, QValidationLink1 TEXT, QValidationLink2 TEXT, QHint TEXT, QLastValidation TEXT, QNotes TEXT, QMultimediaType TEXT, QMultimediaLink TEXT, QLastAsked TEXT);"); db.execSQL("INSERT INTO questionlist (_id, QID, QQuestion, QAnswer, QOption1, QOption2, QOption3, QCategoryTagLvl1, QCategoryTagLvl2, QOptionalTag1, QOptionalTag2, QOptionalTag3, QOptionalTag4, QOptionalTag5, QTimePeriod, QDifficultyRating, QGenderBias, QAgeBias, QRegion, QWikiLink, QValidationLink1, QValidationLink2, QHint, QLastValidation, QNotes, QMultimediaType, QMultimediaLink, QLastAsked)"+ "VALUES (null,'Q00001','Example','Ans1','Q1','Q2','Q3','Q4','','','','','','','','','','','','','','','','','','','','')"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME); onCreate(db); } } Any suggestions at all would be great. I have tried debugging which suggests that the database does not exist. Thanks in advance for your assistance.

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  • How can i pull an image and data from a Database?

    - by user1851377
    I am trying to pull data from a Database using C#.net and use a Foreach loop to make it visible on a page. Every time i run the code i only get one item that shows up when i know that there is at least 7 items in the DB. i have placed the code below for the C#. SqlConnection oConnection = new SqlConnection(ConfigurationManager.ConnectionStrings["HomeGrownEnergyConnectionString"].ToString()); string sqlEnergy = "Select * from Product p where p.ProductTypeId=3"; SqlCommand oCmd = new SqlCommand(sqlEnergy, oConnection); DataTable dtenergy = new DataTable(); SqlDataAdapter oDa = new SqlDataAdapter(oCmd); try { oConnection.Open(); ; oDa.Fill(dtenergy); } catch (Exception ex) { lblnodata.Text = ex.Message; return; } finally { oConnection.Close(); } DataTableReader results = dtenergy.CreateDataReader(); if (results.HasRows) { results.Read(); foreach(DataRow result in dtenergy.Rows) { byte[] imgProd = result["ThumnailLocation"] as byte[]; ID.Text = result["ProductID"].ToString(); Name.Text = result["Name"].ToString(); price.Text = FormatPriceColumn(result["Price"].ToString()); } } Here is the code for the asp.net. <div> <asp:Image ID="imgProd" CssClass="ProdImg" runat="server" /> <asp:Label runat="server" ID="ID" /> <asp:Label runat="server" ID="Name" /> <asp:Label runat="server" ID="price" /> <asp:TextBox ID="txtQty" MaxLength="3" runat="server" Width="30px" /> <asp:Button runat="server" ID="Addtocart" Text="Add To Cart" CommandName="AddToCart" ItemStyle-CssClass="btnCol" /> If someone could please help me that would be great thanks.

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  • LESS THAN OR EQUAL TO IN Oracle SQL

    - by Jasim
    updated_date = 08-Jun-2010; I have a query like this select * from asd whre updated_date <= todate('08-Jun-2010', 'dd-MM-yy'); but i am not getting any result. it is wotking only if todate is 09-Jun-2010... ie my equalto operator is not working properly. y is it like that ny help?

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  • Load Empty Database table

    - by john White
    I am using SQLexpress and VS2008. I have a DB with a table named "A", which has an IdentitySpecification column named ID. The ID is auto-incremented. Even if the row is deleted, the ID still increases. After several data manipulation, the current ID has reached 15, for example. When I run the application if there's at least 1 row: if I add a new row, the new ID is 16. Everything is fine. If the table is empty (no row): if I add a new row, the new ID is 0, which is an error (I think). And further data manipulation (eg. delete or update) will result in an unhandled exception. Has anyone encountered this? PS. In my table definition, the ID has been selected as follow: Identity Increment = 1; Identity Seed =1; The DB load code is: dataSet = gcnew DataSet(); dataAdapter->Fill(dataSet,"A"); dataTable=dataSet->Tables["A"]; dbConnection->Open(); The Update button method dataAdapter->Update(dataSet,"tblInFlow"); dataSet->AcceptChanges(); dataTable=dataSet->Tables["tblInFlow"]; dataGrid->DataSource=dataTable; If I press Update: if there's at least a row: the datagrid view updates and shows the table correctly. if there's nothing in the table (no data row), the Add method will add a new row, but from ID 0. If I close the program and restart it again: the ID would be 16, which is correct. This is the add method row=dataTable->NewRow(); row["column1"]="something"; dataTable->Rows->Add(row); dataAdapter->Update(dataSet,"A"); dataSet->AcceptChanges(); dataTable=dataSet->Tables["A"];

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  • Relation to multiple tables of different types for rating?

    - by Tronic
    i have a table structure like this Products Team Images and want to implement a rating/commenting-feature, where users can rate each entry of all tables. what's the best way to make a single rating table? e.g. a user votes a a product and a team entry, and it should be possible to get alle these entries from a single table. what kind of table-structure is best for this purpose? i hope, my questions is clear enough :/ thanks in advance!

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  • customizing rowsource query in combobox ACCESS

    - by every_answer_gets_a_point
    i have 4 comboboxes and each of them need to have the same query in the rowsource, except there is a slight variation on each query if rowsource = somequery i need it to be select * from somequery where something like 'something1'; the next one needs to be select * from somequery where something like 'something2'; is there a way to customize the rowsource property in this way?

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  • Subquery with multiple results combined into a single field?

    - by Todd
    Assume I have these tables, from which i need to display search results in a browser: Table: Containers id | name 1 Big Box 2 Grocery Bag 3 Envelope 4 Zip Lock Table: Sale id | date | containerid 1 20100101 1 2 20100102 2 3 20091201 3 4 20091115 4 Table: Items id | name | saleid 1 Barbie Doll 1 2 Coin 3 3 Pop-Top 4 4 Barbie Doll 2 5 Coin 4 I need output that looks like this: itemid itemname saleids saledates containerids containertypes 1 Barbie Doll 1,2 20100101,20100102 1,2 Big Box, Grocery Bag 2 Coin 3,4 20091201,20091115 3,4 Envelope, Zip Lock 3 Pop-Top 4 20091115 4 Zip Lock The important part is that each item type only gets one record/row in the return on the screen. I accomplished this in the past by returning multiple rows of the same item and using a scripting language to limit the output. However, this makes the ui overly complicated and loopy. So, I'm hoping I can get the database to spit out only as many records as there are rows to display. This example may be a bit extreme because of the 2 joins needed to get to the container from the item (through the sale table). I'd be happy for just an example query that outputs this: itemid itemname saleids saledates 1 Barbie Doll 1,2 20100101,20100102 2 Coin 3,4 20091201,20091115 3 Pop-Top 4 20091115 I can only return a single result in a subquery, so I'm not sure how to do this.

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  • Indexing table with duplicates MySQL/MSSQL with millions of records

    - by Tesnep
    I need help in indexing in MySQL. I have a table in MySQL with following rows: ID Store_ID Feature_ID Order_ID Viewed_Date Deal_ID IsTrial The ID is auto generated. Store_ID goes from 1 - 8. Feature_ID from 1 - let's say 100. Viewed Date is Date and time on which the data is inserted. IsTrial is either 0 or 1. You can ignore Order_ID and Deal_ID from this discussion. There are millions of data in the table and we have a reporting backend that needs to view the number of views in a certain period or overall where trial is 0 for a particular store id and for a particular feature. The query takes the form of: select count(viewed_date) from theTable where viewed_date between '2009-12-01' and '2010-12-31' and store_id = '2' and feature_id = '12' and Istrial = 0 In MSSQL you can have a filtered index to use for Istrial. Is there anything similar to this in MySQL? Also, Store_ID and Feature_ID have a lot of duplicate data. I created an index using Store_ID and Feature_ID. Although this seems to have decreased the search period, I need better improvement than this. Right now I have more than 4 million rows. To search for a particular query like the one above, it looks at 3.5 million rows in order to give me the count of 500k rows. PS. I forgot to add view_date filter in the query. Now I have done this.

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  • Session or Query

    - by Khou
    Should I store the user's ID, name & email address in a session variable or should I query for the user's user's ID, name & email address everytime i need to use it?

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  • Search field based on multiple parameter

    - by Manoj Wadhwani
    Can anybody modify this , when i insert Emp. name it go to first search and it does not check other paramete could you plz modify this sp for exact search on based on parameter. --select * from Training_TRNS --USP_SearchEmployee '','2008-04-18 00:00:00.000','','','','','' alter Procedure USP_SearchEmployee @EmpName varchar(100)=null, @DateFrom varchar(100)=null, @DateTo varchar(100)=null, @CourseName varchar(100)=null, @JobFunction varchar(100)=null, @Region varchar(100)=null, @Status varchar(100)=null AS BEGIN if (@EmpName!='' and @EmpName is not null) BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS where EmpName like '%'+@EmpName+'%' END ELSE IF (@CourseName!='' and @CourseName is not null) BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS where SpeCourse_ID like '%'+@CourseName+'%' END ELSE IF (@JobFunction!='' and @JobFunction is not null) BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS where EmpJobFunction like '%'+@JobFunction+'%' END ELSE IF (@Region!='' and @Region is not null) BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS where EmpRegion like '%'+@Region+'%' END ELSE IF (@Status!='' and @Status is not null) BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS where Status like '%'+@Status+'%' END ELSE IF (@DateFrom!='' and @DateFrom is not null) BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS where convert(varchar,DueDate,101) like '%'+convert(varchar,@DateFrom,101)+'%' END Else BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS END END

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  • Only show certain items in a mysql database using php and time()

    - by Jon
    Is there a way to only show the items that are older than a certain date in a php mysql array? I'm using this query method and sorting by lastpost_cl: $query="SELECT * FROM properties ORDER BY lastpost_cl"; $result=mysql_query($query); $num = mysql_num_rows ($result); mysql_close(); and I was thinking the way of checking the time would be: if (time() <= strtotime($lastpost_cl)) { } How can I combine the two and only show lastpost_cl that are older that the current time?

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  • How to analyse Wikipedia article's data base with R?

    - by Tal Galili
    Hi all, This is a "big" question, that I don't know how to start, so I hope some of you can give me a direction. And if this is not a "good" question, I will close the thread with an apology. I wish to go through the database of Wikipedia (let's say the English one), and do statistics. For example, I am interested in how many active editors (which should be defined) Wikipedia had at each point of time (let's say in the last 2 years). I don't know how to build such a database, how to access it, how to know which types of data it has and so on. So my questions are: What tools do I need for this (besides basic R) ? MySQL on my computer? RODBC database connection? How do you start planning for such a project?

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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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  • Naming of boolean column in database table

    - by Space Cracker
    I have 'Service' table and the following column description as below Is User Verification Required for service ? Is User's Email Activation Required for the service ? Is User's Mobile Activation required for the service ? I Hesitate in naming these columns as below IsVerificationRequired IsEmailActivationRequired IsMobileActivationRequired or RequireVerification RequireEmailActivation RequireMobileActivation I can't determined which way is the best .So, Is one of the above suggested name is the best or is there other better ones ?

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  • IN 'mytextfile.txt' syntax - access

    - by I__
    i would like to use this syntax to update a table in access based on data from a txtfile. fenton in his comments on this answer: http://stackoverflow.com/questions/2992168/read-text-file-line-by-line-and-insert-update-values-in-table/2992337#2992337 said that this is possible and i would like to see the exact syntax please

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  • Selecting financial values from db stored as text

    - by Midhat
    I have some financial values stored as text in a mysql db. the significance of financial is that negative numbers are stored enclosed in paranthesis. is there a way to automatically get the numeric value associated with that text. (like '5' shoudl be retuned as 5 and '(5)' should be returned as -5)

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  • c# Column datatype Date type (NOT DateTime)

    - by Sha Le
    Hi All: I want know is there good way to detect Column DataType for Date field (NOT DateTime)? This what currently I do: switch (dt.Columns[col].DataType.FullName) { case "System.DateTime": formatedVal = Formatter.GetDateTime(val); break; // which is NOT possible, but something equivalent am looking for case "System.Date": formatedVal = Formatter.GetDate(val); break; default: formatedVal = val.ToString(); break; } Thanks a bunch. :-)

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  • Violation of primary key constraint, multiple users

    - by MC.
    Lets say UserA and UserB both have an application open and are working with the same type of data. UserA inserts a record into the table with value 10 (PrimaryKey='A'), UserB does not currently see the value UserA entered and attempts to insert a new value of 20 (PrimaryKey='A'). What I wanted in this situation was a DBConcurrencyException, but instead what I have is a primary key violation. I understand why, but I have no idea how to resolve this. What is a good practice to deal with such a circumstance? I do not want to merge before updating the database because I want an error to inform the user that multiple users updated this data.

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  • change postgres date format

    - by Jay
    Is there a way to change the default format of a date in Postgres? Normally when I query a Postgres database, dates come out as yyyy-mm-dd hh:mm:ss+tz, like 2011-02-21 11:30:00-05. But one particular program the dates come out yyyy-mm-dd hh:mm:ss.s, that is, there is no time zone and it shows tenths of a second. Apparently something is changing the default date format, but I don't know what or where. I don't think it's a server-side configuration parameter, because I can access the same database with a different program and I get the format with the timezone. I care because it appears to be ignoring my "set timezone" calls in addition to changing the format. All times come out EST. Additional info: If I write "select somedate from sometable" I get the "no timezone" format. But if I write "select to_char(somedate::timestamptz, 'yyyy-mm-dd hh24:mi:ss-tz')" then timezones work as I would expect. This really sounds to me like something is setting all timestamps to implicitly be "to_char(date::timestamp, 'yyyy-mm-dd hh24:mi:ss.m')". But I can't find anything in the documentation about how I would do this if I wanted to, nor can I find anything in the code that appears to do this. Though as I don't know what to look for, that doesn't prove much.

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  • Generating a set of files containing dumps of individual tables in a way that guarantees database co

    - by intuited
    I'd like to dump a MySQL database in such a way that a file is created for the definition of each table, and another file is created for the data in each table. I'd like this to be done in a way that guarantees database integrity by locking the entire database for the duration of the dump. What is the best way to do this? Similarly, what's the best way to lock the database while restoring a set of these dump files? edit I can't assume that mysql will have permission to write to files.

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  • SELECT set of most recent id, amount FROM table, where id occurs many times

    - by Jon Cram
    I have a table recording the amount of data transferred by a given service on a given date. One record is entered daily for a given service. I'd like to be able to retrieve the most recent amount for a set of services. Example data set: serviceId | amount | date ------------------------------- 1 | 8 | 2010-04-12 2 | 11 | 2010-04-12 2 | 14 | 2010-04-11 3 | 9 | 2010-04-11 1 | 6 | 2010-04-10 2 | 5 | 2010-04-10 3 | 22 | 2010-04-10 4 | 17 | 2010-04-19 Desired response (service ids 1,2,3): serviceId | amount | date ------------------------------- 1 | 8 | 2010-04-12 2 | 11 | 2010-04-12 3 | 9 | 2010-04-11 Desired response (service ids 2, 4): serviceId | amount | date ------------------------------- 2 | 11 | 2010-04-12 4 | 17 | 2010-04-19 This retrieves the equivalent as running the following once per serviceId: SELECT serviceId, amount, date FROM table WHERE serviceId = <given serviceId> ORDER BY date DESC LIMIT 0,1 I understand how I can retrieve the data I want in X queries. I'm interested to see how I can retrieve the same data using either a single query or at the very least less than X queries. I'm very interested to see what might be the most efficient approach. The table currently contains 28809 records. I appreciate that there are other questions that cover selecting the most recent set of records. I have examined three such questions but have been unable to apply the solutions to my problem.

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  • [C#] How to create a constructor of a class that return a collection of instances of that class?

    - by codemonkie
    My program has the following class definition: public sealed class Subscriber { private subscription; public Subscriber(int id) { using (DataContext dc = new DataContext()) { this.subscription = dc._GetSubscription(id).SingleOrDefault(); } } } ,where _GetSubscription() is a sproc which returns a value of type ISingleResult<_GetSubscriptionResult> Say, I have a list of type List<int> full of 1000 ids and I want to create a collection of subscribers of type List<Subscriber>. How can I do that without calling the constructor in a loop for 1000 times? Since I am trying to avoid switching the DataContext on/off so frequently that may stress the database. TIA.

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  • Can a primary key be equal to a different column?

    - by eric
    I know that a primary key must be unique, but is it okay for a primary key to be equal to a different column in the same table by coincidence? For instance, I have 2 tables. One table is called person that holds information about a person (ID, email, telephone, address, name). The other table is staff (ID, pID(person ID), salary, position). In staff the ID column is the primary key and is used to uniquely identify a staff member. The number is from 1 - 100. However, the pID (person ID) may be equal to the ID. For instance the staff ID may be 1 and the pID that it references to may be equal to 1. Is that okay?

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