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  • Enforcing a query in MySql to use a specific index

    - by Hossein
    Hi, I have large table. consisting of only 3 columns (id(INT),bookmarkID(INT),tagID(INT)).I have two BTREE indexes one for each bookmarkID and tagID columns.This table has about 21 Million records. I am trying to run this query: SELECT bookmarkID,COUNT(bookmarkID) AS count FROM bookmark_tag_map GROUP BY tagID,bookmarkID HAVING tagID IN (-----"tagIDList"-----) AND count >= N which takes ages to return the results.I read somewhere that if make an index in which it has tagID,bookmarkID together, i will get a much faster result. I created the index after some time. Tried the query again, but it seems that this query is not using the new index that I have made.I ran EXPLAIN and saw that it is actually true. My question now is that how I can enforce a query to use a specific index? also comments on other ways to make the query faster are welcome. Thanks

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  • What is the Null Character literal in TSQL?

    - by David in Dakota
    I am wondering what the literal for a Null character (e.g. '\0') is in TSQL. Note: not a NULL field value, but the null character (see link). I have a column with a mix of typical and a null character. I'm trying to replace the null character with a different value. I would have thought that the following would work but it is unsuccessfull: select REPLACE(field_with_nullchar, char(0), ',') from FOO where BAR = 20

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  • Are database triggers evil?

    - by WW
    Are database triggers a bad idea? In my experience they are evil, because they can result in surprising side effects, and are difficult to debug (especially when one trigger fires another). Often developers do not even think of looking if there is a trigger. On the other hand, it seems like if you have logic that must occur evertime a new FOO is created in the database then the most foolproof place to put it is an insert trigger on the FOO table. The only time we're using triggers is for really simple things like setting the ModifiedDate.

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  • Split function in where clause

    - by abhishek-khandelwal
    hello friends I am using following query in linq In product table following type of data are stored abc-def bcd=fgh abc-xyz var query=from prod in db.Product join cat in db.category on prod.categoryId=cat.categoryID where prod.productName.split('-')[0]=="abc" but in that query it product annoumous problem Please give some suggestion to split in where caluse

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  • MSSQL 2008 FTS CONTAINSTABLE Not Returning More Than Five Rows

    - by Elijah Glover
    I have a single table called "Indexes", it contains one nvarchar and three ntext columns (all Full Text Indexes). Index is up to date. CONTAINSTABLE(Indexes, *), 'test', 5) //5 results No matter what I change the above keyword too, it only returns the first 3-5 results. It should roughly return 90-120 results, for the above query. SELECT count(*) FROM Indexes WHERE [Description] like '%test%' //122 results How would I start to troubleshoot this problem?

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  • Select from multiple tables, remove duplicates

    - by staze
    I have two tables in a SQLite DB, and both have the following fields: idnumber, firstname, middlename, lastname, email, login One table has all of these populated, the other doesn't have the idnumber, or middle name populated. I'd LIKE to be able to do something like: select idnumber, firstname, middlename, lastname, email, login from users1,users2 group by login; But I get an "ambiguous" error. Doing something like: select idnumber, firstname, middlename, lastname, email, login from users1 union select idnumber, firstname, middlename, lastname, email, login from users2; LOOKS like it works, but I see duplicates. my understanding is that union shouldn't allow duplicates, but maybe they're not real duplicates since the second user table doesn't have all the fields populated (e.g. "20, bob, alan, smith, [email protected], bob" is not the same as "NULL, bob, NULL, smith, [email protected], bob"). Any ideas? What am I missing? All I want to do is dedupe based on "login". Thanks!

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  • Embedding generic sql queries into c# program

    - by Pooja Balkundi
    Okay referring to my first question code in the main, I want the user to enter employee name at runtime and then i take this name which user has entered and compare it with the e_name of my emp table , if it exists i want to display all information of that employee , how can I achieve this ? using System; using System.Collections.Generic; using System.Linq; using System.Windows.Forms; using MySql.Data.MySqlClient; namespace ConnectCsharppToMySQL { public class DBConnect { private MySqlConnection connection; private string server; private string database; private string uid; private string password; string name; //Constructor public DBConnect() { Initialize(); } //Initialize values private void Initialize() { server = "localhost"; database = "test"; uid = "root"; password = ""; string connectionString; connectionString = "SERVER=" + server + ";" + "DATABASE=" + database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";"; connection = new MySqlConnection(connectionString); } //open connection to database private bool OpenConnection() { try { connection.Open(); return true; } catch (MySqlException ex) { //When handling errors, you can your application's response based //on the error number. //The two most common error numbers when connecting are as follows: //0: Cannot connect to server. //1045: Invalid user name and/or password. switch (ex.Number) { case 0: MessageBox.Show("Cannot connect to server. Contact administrator"); break; case 1045: MessageBox.Show("Invalid username/password, please try again"); break; } return false; } } //Close connection private bool CloseConnection() { try { connection.Close(); return true; } catch (MySqlException ex) { MessageBox.Show(ex.Message); return false; } } //Insert statement public void Insert() { string query = "INSERT INTO emp (e_name, age) VALUES('Pooja R', '21')"; //open connection if (this.OpenConnection() == true) { //create command and assign the query and connection from the constructor MySqlCommand cmd = new MySqlCommand(query, connection); //Execute command cmd.ExecuteNonQuery(); //close connection this.CloseConnection(); } } //Update statement public void Update() { string query = "UPDATE emp SET e_name='Peachy', age='22' WHERE e_name='Pooja R'"; //Open connection if (this.OpenConnection() == true) { //create mysql command MySqlCommand cmd = new MySqlCommand(); //Assign the query using CommandText cmd.CommandText = query; //Assign the connection using Connection cmd.Connection = connection; //Execute query cmd.ExecuteNonQuery(); //close connection this.CloseConnection(); } } //Select statement public List<string>[] Select() { string query = "SELECT * FROM emp where e_name=(/*I WANT USER ENTERED NAME TO GET INSERTED HERE*/)"; //Create a list to store the result List<string>[] list = new List<string>[3]; list[0] = new List<string>(); list[1] = new List<string>(); list[2] = new List<string>(); //Open connection if (this.OpenConnection() == true) { //Create Command MySqlCommand cmd = new MySqlCommand(query, connection); //Create a data reader and Execute the command MySqlDataReader dataReader = cmd.ExecuteReader(); //Read the data and store them in the list while (dataReader.Read()) { list[0].Add(dataReader["e_id"] + ""); list[1].Add(dataReader["e_name"] + ""); list[2].Add(dataReader["age"] + ""); } //close Data Reader dataReader.Close(); //close Connection this.CloseConnection(); //return list to be displayed return list; } else { return list; } } public static void Main(String[] args) { DBConnect db1 = new DBConnect(); Console.WriteLine("Initializing"); db1.Initialize(); Console.WriteLine("Search :"); Console.WriteLine("Enter the employee name"); db1.name = Console.ReadLine(); db1.Select(); Console.ReadLine(); } } }

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  • Tables with no Primary Key

    - by Matt Hamilton
    I have several tables whose only unique data is a uniqueidentifier (a Guid) column. Because guids are non-sequential (and they're client-side generated so I can't use newsequentialid()), I have made a non-primary, non-clustered index on this ID field rather than giving the tables a clustered primary key. I'm wondering what the performance implications are for this approach. I've seen some people suggest that tables should have an auto-incrementing ("identity") int as a clustered primary key even if it doesn't have any meaning, as it means that the database engine itself can use that value to quickly look up a row instead of having to use a bookmark. My database is merge-replicated across a bunch of servers, so I've shied away from identity int columns as they're a bit hairy to get right in replication. What are your thoughts? Should tables have primary keys? Or is it ok to not have any clustered indexes if there are no sensible columns to index that way?

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  • Sending changes from multiple tables in disconnected dataset to SQLServer...

    - by Stecy
    We have a third party application that accept calls using an XML RPC mechanism for calling stored procs. We send a ZIP-compressed dataset containing multiple tables with a bunch of update/delete/insert using this mechanism. On the other end, a CLR sproc decompress the data and gets the dataset. Then, the following code gets executed: using (var conn = new SqlConnection("context connection=true")) { if (conn.State == ConnectionState.Closed) conn.Open(); try { foreach (DataTable table in ds.Tables) { string columnList = ""; for (int i = 0; i < table.Columns.Count; i++) { if (i == 0) columnList = table.Columns[0].ColumnName; else columnList += "," + table.Columns[i].ColumnName; } var da = new SqlDataAdapter("SELECT " + columnList + " FROM " + table.TableName, conn); var builder = new SqlCommandBuilder(da); builder.ConflictOption = ConflictOption.OverwriteChanges; da.RowUpdating += onUpdatingRow; da.Update(ds, table.TableName); } } catch (....) { ..... } } Here's the event handler for the RowUpdating event: public static void onUpdatingRow(object sender, SqlRowUpdatingEventArgs e) { if ((e.StatementType == StatementType.Update) && (e.Command == null)) { e.Command = CreateUpdateCommand(e.Row, sender as SqlDataAdapter); e.Status = UpdateStatus.Continue; } } and the CreateUpdateCommand method: private static SqlCommand CreateUpdateCommand(DataRow row, SqlDataAdapter da) { string whereClause = ""; string setClause = ""; SqlConnection conn = da.SelectCommand.Connection; for (int i = 0; i < row.Table.Columns.Count; i++) { char quoted; if ((row.Table.Columns[i].DataType == Type.GetType("System.String")) || (row.Table.Columns[i].DataType == Type.GetType("System.DateTime"))) quoted = '\''; else quoted = ' '; string val = row[i].ToString(); if (row.Table.Columns[i].DataType == Type.GetType("System.Boolean")) val = (bool)row[i] ? "1" : "0"; bool isPrimaryKey = false; for (int j = 0; j < row.Table.PrimaryKey.Length; j++) { if (row.Table.PrimaryKey[j].ColumnName == row.Table.Columns[i].ColumnName) { if (whereClause != "") whereClause += " AND "; if (row[i] == DBNull.Value) whereClause += row.Table.Columns[i].ColumnName + "=NULL"; else whereClause += row.Table.Columns[i].ColumnName + "=" + quoted + val + quoted; isPrimaryKey = true; break; } } /* Only values for column that is not a primary key can be modified */ if (!isPrimaryKey) { if (setClause != "") setClause += ", "; if (row[i] == DBNull.Value) setClause += row.Table.Columns[i].ColumnName + "=NULL"; else setClause += row.Table.Columns[i].ColumnName + "=" + quoted + val + quoted; } } return new SqlCommand("UPDATE " + row.Table.TableName + " SET " + setClause + " WHERE " + whereClause, conn); } However, this is really slow when we have a lot of records. Is there a way to optimize this or an entirely different way to send lots of udpate/delete on several tables? I would really much like to use TSQL for this but can't figure a way to send a dataset to a regular sproc. Additional notes: We cannot directly access the SQLServer database. We tried without compression and it was slower.

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  • How does Select statement works in a Dynamic Linq Query?

    - by Richard77
    Hello, 1) I've a Product table with 4 columns: ProductID, Name, Category, and Price. Here's the regular linq to query this table. public ActionResult Index() { private ProductDataContext db = new ProductDataContext(); var products = from p in db.Products where p.Category == "Soccer" select new ProductInfo { Name = p.Name, Price = p.Price} return View(products); } Where ProductInfo is just a class that contains 2 properties (Name and Price). The Index page Inherits ViewPage - IEnumerable - ProductInfo. Everything works fine. 2) To dynamicaly execute the above query, I do this: Public ActionResult Index() { var products = db.Products .Where("Category = \"Soccer\"") .Select(/* WHAT SOULD I WRITE HERE TO SELECT NAME & PRICE?*/) return View(products); } I'm using both 'System.Lind.Dynamic' namespace and the DynamicLibrary.cs (downloaded from ScottGu blog). Here are my questions: What expression do I use to select only Name and Price? (Most importantly) How do I retrieve the data in my view? (i.e. What type the ViewPage inherits? ProductInfo?)

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  • Union and If Exists - not working together - Please help

    - by needshelp
    I need to get dummy values if they do no rows returned from table. The If exists works by itself, but gives error with a Union. Can someone please guide me with a solution or a workaround? create table test1 (col1 varchar(10)) create table test2 (col1 varchar(10)) create table test3 (col1 varchar(10)) insert test1 values ('test1-row1') insert test1 values ('test1-row2') insert test2 values ('test2-row1') insert test2 values ('test2-row2') select col1 from test1 union select col1 from test2 union if exists (select * from test3) select col1 from test3 else select 'dummy'

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  • How to designing a generic databse whos layout may change over time?

    - by mawg
    Here's a tricky one - how do I programatically create and interrogate a database who's contents I can't really foresee? I am implementing a generic input form system. The user can create PHP forms with a WYSIWYG layout and use them for any purpose he wishes. He can also query the input. So, we have three stages: a form is designed and generated. This is a one-off procedure, although the form can be edited later. This designs the database. someone or several people make use of the form - say for daily sales reports, stock keeping, payroll, etc. Their input to the forms is written to the database. others, maybe management, can query the database and generate reports. Since these forms are generic, I can't predict the database structure - other than to say that it will reflect HTML form fields and consist of a the data input from collection of edit boxes, memos, radio buttons and the like. Questions and remarks: A) how can I best structure the database, in terms of tables and columns? What about primary keys? My first thought was to use the control name to identify each column, then I realized that the user can edit the form and rename, so that maybe "name" becomes "employee" or "wages" becomes ":salary". I am leaning towards a unique number for each. B) how best to key the rows? I was thinking of a timestamp to allow me to query and a column for the row Id from A) C) I have to handle column rename/insert/delete. Foe deletion, I am unsure whether to delete the data from the database. Even if the user is not inputting it from the form any more he may wish to query what was previously entered. Or there may be some legal requirements to retain the data. Any gotchas in column rename/insert/delete? D) For the querying, I can have my PHP interrogate the database to get column names and generate a form with a list where each entry has a database column name, a checkbox to say if it should be used in the query and, based on column type, some selection criteria. That ought to be enough to build searches like "position = 'senior salesman' and salary 50k". E) I probably have to generate some fancy charts - graphs, histograms, pie charts, etc for query results of numerical data over time. I need to find some good FOSS PHP for this. F) What else have I forgotten? This all seems very tricky to me, but I am database n00b - maybe it is simple to you gurus?

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  • Check if access table exists

    - by HasanGursoy
    I want to log web site visits' IP, datetime, client and refferer data to access database but I'm planning to log every days log data in separate tables in example logs for 06.06.2010 will be logged in 2010_06_06 named table. When date is changed I'll create a table named 2010_06_07. But the problem is if this table is already created. Any suggestions how to check if table exists in Access?

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  • What are the benefits of left outer join vs nested aggregate selects to find the newest rows in a table?

    - by RenderIn
    I'm doing: select * from mytable y where y.year = (select max(yi.year) from mytable yi where yi.person = y.person) Is that better or worse from a performance aspect than: select y.* from mytable y left outer join mytable y2 on y.year < y2.year and y.person = y2.person where y2.year is null The explain plan/anecdotal evidence is inconclusive so I am wondering if in general one is better than the other.

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  • Should I include user_id in multiple tables?

    - by Drarok
    I'm at the planning stages of a multi-user application where each user will only have access their own data. There'll be a few tables that relate to each other, so I could use JOINs to ensure they're accessing only their data, but should I include user_id in each table? Would this be faster? It would certainly make some of the queries easier in the long run. Thanks!

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  • Select count() max() Date

    - by DAVID
    I have a table with shifts history along with emp ids. I'm using this query to retrieve a list of employees and their total shifts by specifying the range to count from: SELECT ope_id, count(ope_id) FROM operator_shift WHERE ope_shift_date >=to_date( '01-MAR-10','dd-mon-yy') and ope_shift_date <= to_date('31-MAR-10','dd-mon-yy') GROUP BY OPE_ID which gives OPE_ID COUNT(OPE_ID) 1 14 2 7 3 6 4 6 5 2 6 5 7 2 8 1 9 2 10 4 10 rows selected. How do I choose the employee with the highest number of shifts under the specified range date?

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  • Sqlserver 2005 Replication issue

    - by Francesco
    Hi, I have a peer to peer Merge Replication from two Sqlserver 2005. The first Sqlserver is both the publisher and distribuitor. All works fine but if the VPN goes down for a couple of hours the replication goes down too and I need to manually restart the sqlserver agent. In the Sqlserver Agent properties I have set the two option about the agent failover but nothing. How I can set an automatic restart of sqlserver agent when the VPN goes down? Thanks

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  • What is the proper way to create a recursive entity in the Entity Framework?

    - by Orion Adrian
    I'm currently using VS 2010 RC, and I'm trying to create a model that contains a recursive self-referencing entity. Currently when I import the entity from the model I get an error indicating that the parent property cannot be part of the association because it's set to 'Computed' or 'Identity', though I'm not sure why it does it that way. I've been hand-editing the file to get around that error, but then the model simply doesn't work. What is the proper way to get recursive entities to work in the Entity Framework. CREATE TABLE [dbo].[Appointments]( [AppointmentId] [int] IDENTITY(1,1) NOT NULL, [Description] [nvarchar](1024) NULL, [Start] [datetime] NOT NULL, [End] [datetime] NOT NULL, [Username] [varchar](50) NOT NULL, [RecurrenceRule] [nvarchar](1024) NULL, [RecurrenceState] [varchar](20) NULL, [RecurrenceParentId] [int] NULL, [Annotations] [nvarchar](50) NULL, [Application] [nvarchar](100) NOT NULL, CONSTRAINT [PK_Appointments] PRIMARY KEY CLUSTERED ( [AppointmentId] ASC ) ) GO ALTER TABLE [dbo].[Appointments] WITH CHECK ADD CONSTRAINT [FK_Appointments_ParentAppointments] FOREIGN KEY([RecurrenceParentId]) REFERENCES [dbo].[Appointments] ([AppointmentId]) GO ALTER TABLE [dbo].[Appointments] CHECK CONSTRAINT [FK_Appointments_ParentAppointments] GO

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  • Advice about insert into SQLCE

    - by Alexander
    i am inserting about 1943 records by these function into SQLCE.This is my insert function.Parameters come from StringReader(string comes from webservice).This function executes 1943 times and takes about 20 seconds.I dropped table's indexes,what can i do to improve it?I create just 1 time mycomm and sqlceresultset. Public Function Insert_Function(ByVal f_Line() As String, ByRef myComm As SqlCeCommand, ByRef rs As SqlCeResultSet) As String Try Dim rec As SqlCeUpdatableRecord = rs.CreateRecord() rec.SetInt32(0, IIf(f_Line(1) = "", DBNull.Value, f_Line(1))) rec.SetInt32(1, IIf(f_Line(2) = "", DBNull.Value, f_Line(2))) rec.SetInt32(2, IIf(f_Line(3) = "", DBNull.Value, f_Line(3))) rec.SetInt32(3, IIf(f_Line(4) = "", DBNull.Value, f_Line(4))) rec.SetValue(4, IIf(f_Line5(5) = "", DBNull.Value, f_Line(5))) rs.Insert(rec) rec = Nothing Catch ex As Exception strerr_col = ex.Message End Try Return strerr_col End Function

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  • Using outer query result in a subquery in postgresql

    - by brad
    I have two tables points and contacts and I'm trying to get the average points.score per contact grouped on a monthly basis. Note that points and contacts aren't related, I just want the sum of points created in a month divided by the number of contacts that existed in that month. So, I need to sum points grouped by the created_at month, and I need to take the count of contacts FOR THAT MONTH ONLY. It's that last part that's tricking me up. I'm not sure how I can use a column from an outer query in the subquery. I tried something like this: SELECT SUM(score) AS points_sum, EXTRACT(month FROM created_at) AS month, date_trunc('MONTH', created_at) + INTERVAL '1 month' AS next_month, (SELECT COUNT(id) FROM contacts WHERE contacts.created_at <= next_month) as contact_count FROM points GROUP BY month, next_month ORDER BY month So, I'm extracting the actual month that my points are being summed, and at the same time, getting the beginning of the next_month so that I can say "Get me the count of contacts where their created at is < next_month" But it complains that column next_month doesn't exist This is understandable as the subquery knows nothing about the outer query. Qualifying with points.next_month doesn't work either. So can someone point me in the right direction of how to achieve this? Tables: Points score | created_at 10 | "2011-11-15 21:44:00.363423" 11 | "2011-10-15 21:44:00.69667" 12 | "2011-09-15 21:44:00.773289" 13 | "2011-08-15 21:44:00.848838" 14 | "2011-07-15 21:44:00.924152" Contacts id | created_at 6 | "2011-07-15 21:43:17.534777" 5 | "2011-08-15 21:43:17.520828" 4 | "2011-09-15 21:43:17.506452" 3 | "2011-10-15 21:43:17.491848" 1 | "2011-11-15 21:42:54.759225" sum, month and next_month (without the subselect) sum | month | next_month 14 | 7 | "2011-08-01 00:00:00" 13 | 8 | "2011-09-01 00:00:00" 12 | 9 | "2011-10-01 00:00:00" 11 | 10 | "2011-11-01 00:00:00" 10 | 11 | "2011-12-01 00:00:00"

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  • ASP.NET MVC- Bizarre problem - suddennly lost all LINQTO SQL data context objects

    - by MikeD
    I was making an edit to a long existing project. Specifically I added some fields to a table and had to delete the table from the LINQTOSQL designer and re-add it. doesn't Also had to do the same for a view. Mode some other code changes and went to build . Now my project won't build because it can't resolve any of the data context objects (all tables and views) in my code. I don't know what I did or how this happeened. I have many tables and views in the project's L2S data context so I don't wont to try and do over. Please any suggestions on how to resolve this problem are greatly appreciated. Desparate! The error messages I am getting are the familiar The type or namespace name 'equipment' could not be found (are you missing a using directive or an assembly reference?)

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