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  • is NATURAL JOIN any better than SELECT FROM WHERE in terms of performance ?

    - by ashy_32bit
    Today I got into a debate with my project manager about Cartesian products. He says a 'natural join' is somehow much better than using 'select from where' because the later cause the db engine to internally perform a Cartesian product but the former uses another approach that prevents this. As far as I know, the natural join syntax is not any different in anyway than 'select from where' in terms of performance or meaning, I mean you can use either based on your taste. SELECT * FROM table1,table2 WHERE table1.id=table2.id SELECT * FROM table1 NATURAL JOIN table2 please elaborate about the first query causing a Cartesian product but the second one being somehow more smart

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  • Does the order of the columns in a SELECT statement make a difference?

    - by Frank Computer
    This question was inspired by a previous question posted on SO, "Does the order of the WHERE clause make a differnece?". Would it improve a SELECT statement's performance if the the columns used in the WHERE section are placed at the begining of the SELECT statement? example: SELECT customer.id, transaction.id, transaction.efective_date, transaction.a, [...] FROM customer, transaction WHERE customer.id = transaction.id; I do know that limiting the list of columns to only the needed ones in a SELECT statement improves performance as opposed to using SELECT * because the current list is smaller.

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  • How to handle Foreign Keys with Entity Framework

    - by Jack Marchetti
    I have two entities. Groups. Pools. A Group can create many pools. So I setup my Pool table to have a GroupID foreign key. My code: using (entity _db = new entity()) { Pool p = new Pool(); p.Name = "test"; p.Group.ID = "5"; _db.AddToPool(p); } This doesn't work. I get a null reference exception on p.Group. How do I go about creating a new "Pool" and associating a GroupID?

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  • Showing an image after laoding it from sql database

    - by user330075
    I have a problem showing the image form database in a view Details and a ImageController. Inside the view i have: img src=Url.Action("GetFile","Image", new {id= Model.id}) and in controller: public FileContentResult GetFile(int idl) { //int idl = 32; SqlDataReader rdr; byte[] fileContent = null; ........... return File(,,); } When the view is called, function GetFile it just wont work,but if i cut out the parameter int id1 and i instantiate it as a variable it'l work. public FileContentResult GetFile() { int idl = 32; SqlDataReader rdr; byte[] fileContent = null; ........... return File(,,); } Why?

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  • Transfer Data between databases with postgres

    - by user227932
    I need to transfer some data from another Database. The old database is called paw1.moviesDB and the new database is paw1. The schema of each table are the following Awards (name of the table)(new DB) Id [PK] Serial Award Nominations (name of the table) (old DB) Id [PK] Serial nominations I want to copy the data from old DB to the new DB.

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  • filter by atributs php script

    - by cosy
    I have the table : id id_products id_atribut name value 1 13 8 autdio 2.1 2 13 9 hdd 200 Gb 3 13 10 cd-rom 2 4 20 8 audio 2.1 the problem is, how can i select from this table where id_products=13 and name="audio" and value="2.1" and name="hdd" and value="200 gb" .... How can i do this?

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  • how to order string logically

    - by just_name
    Q: I have the following case : set of letters (grades) A,A+,A-,B,B+,B- stored as strings in the database i wanna to order these grades logically from the small one to the big one ,, but this not what happen in real.. because these are strings the order is: A,A+,A- i wanna ASC A-,A,A+ DESC A+,A,A- i bind those grades in drop down list and i wanna these grades with this logical order in it.. is there any idea how to do something like this..

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  • Facing trouble in retrieving relevant records

    - by Umaid
    SELECT * from MainCategory where Month = 'May' and Day in ((cast(strftime('%d',date('now','-1 day')) as Integer)),(cast(strftime('%d',date('now')) as Integer)),(cast(strftime('%d',date('now','+1 day')) as Integer))); Whenever I run this query in sqlite so it returns me 33 records instead of 3. I am insterested in fetching on 3 records of the current month but unable to do so, so plz assist. --Please note: if you can't assist so plz don't post irrelevant answer. I have also modified and try to make it simple but not achieve Select day, month from MainCategory where Month = 'May' and day in ((date('now','-1 day')),(date('now')),(date('now','+1 day')))

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  • wanted to get all dates in mysql result

    - by PankajK
    I have mysql table called user(id, name, join_on) join on is a date field what I want is to show in each day how many uses has been created I can use group by but it will only give me the dates when users get added like if date 4/12/10 5 users added 4/13/10 2 users added 4/15/10 7 users added here date 4/14/10 is missing and I want listing of all dates in one month. I have one solution for it by creating another table only for adding date and that table will left join my users table on join_on and will give total result but I don't want to do that as for creating that I need to create and add entries in date table please suggest the different approach for doing so. Thank you.

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  • Cakephp Autoconvert find() fields?

    - by Razor Storm
    In cake php I can grab a model's fields by using the find() method. What if I wish to apply a transformation function to the fields? Is there a way to directly accomplish this task? Suppose I have a model called RaceTime with the fields racerId and timeMillis RaceTime +------------+ | Field | +------------+ | id | | racerId | | timeMillis | +------------+ timeMillis is an int specifying how long the race took in milliseconds. Obviously saying a race took 15651 milliseconds isn't very useful to a human reader, and I would wish to convert this to a human readable format. Is there a way to accomplish this directly in find()? Or is the only option to loop through the results after find() finishes?

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  • MSYQL ~ Why does this query only select a single row?

    - by Joe
    SELECT * FROM tbl_houses WHERE (SELECT HousesList FROM tbl_lists WHERE tbl_lists.ID = '123') LIKE CONCAT('% ', tbl_houses.ID, '#') ^ It only selects the row from tbl_houses of the last occuring "tbl_houses.ID" inside tbl_lists.HousesList I need it to select ALL the rows where any ID from tbl_houses exists within tbl_lists.HousesList

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  • MYSQL: COUNT with GROUP BY, LEFT JOIN and WHERE clause doesn't return zero values

    - by Paul Norman
    Hi guys, thanks in advance for any help on this topic! I'm sure this has a very simply answer, but I can't seem to find it (not sure what to search on!). A standard count / group by query may look like this: SELECT COUNT(`t2`.`name`) FROM `table_1` `t1` LEFT JOIN `table_2` `t2` ON `t1`.`key_id` = `t2`.`key_id` GROUP BY `t1`.`any_col` and this works as expected, returning 0 if no rows are found. So does: SELECT COUNT(`t2`.`name`) FROM `table_1` `t1` LEFT JOIN `table_2` `t2` ON `t1`.`key_id` = `t2`.`key_id` WHERE `t1`.`another_column` = 123 However: SELECT COUNT(`t2`.`name`) FROM `table_1` `t1` LEFT JOIN `table_2` `t2` ON `t1`.`key_id` = `t2`.`key_id` WHERE `t1`.`another_column` = 123 GROUP BY `t1`.`any_col` only works if there is at least one row in table_1 and fails miserably returning an empty result set if there are zero rows. I would really like this to return 0! Anyone enlighten me on this? Beer can be provided in exchange if you are in London ;-)

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  • get index name within specific table name

    - by AmRoSH
    I need to check if this index not exist in specific table name not in all tables because this select statement select all indexes under this condition. IF NOT EXISTS (SELECT name from sysindexes WHERE name = 'IDX_InsuranceID') CREATE NONCLUSTERED INDEX [IDX_InsuranceID] ON [dbo].[QuoteInsurances] ( [InsuranceID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 80) ON [PRIMARY] GO Thanks,

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  • Entity diagram with tables that have foreign keys that point to a non-PK column do not show relation

    - by Jason Coyne
    I have two tables parent and child. If I make a foreign key on child that points to the primary key of parent, and then make an entity diagram, the relationship is shown correctly. If I make the foreign key point to a different column, the relationship is not shown. I have tried adding indexes to the column, but it does not have an effect. The database is sqlite, but I am not sure if that has an effect since its all hidden behind ADO.net. How do I get the relationship to work correctly?

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  • Check for duplicate rows in 2 columns before update

    - by user3891378
    I have a table with 4 columns, and I need to check to see if a Column Pair exists before inserting a row into the database: INSERT INTO dbo.tblCallReport_Detail (fkCallReport, fkProductCategory, Discussion, Action) VALUES (?, ?, ?, ?) The pair in question is fkCallReport and fkProductCategory. For example if the row trying to be inserted has fkCallReport = 3 and fkProductCategory = 5, and the database already has both of those values together, it should display an error and ask if they would like to combine the Disuccsion and Action with the current record. Keep in mind I'm doing this in VBA Access 2010 and am still very new.

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  • Removing part of a string in PHP

    - by Nik
    I'm trying to take a query: SHOW TABLES; which will display a bunch of tables with the chat_ prefix. I want to remove the chat_ prefix from the string, format the variable (with a link), and display it. How is this accomplished?

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  • sports league database design

    - by John
    Hello, I'm developing a database to store statistics for a sports league. I'd like to show several tables: - league table that indicates the position of the team in the current and previous fixture - table that shows the position of a team in every fixture in the championship I have a matches table: Matches (IdMatch, IdTeam1, IdTeam2, GoalsTeam1, GoalsTeam2) Whith this table I can calculate the total points of every team based on the matches the team played. But every time I want to show the league table I have to calculate the points. Also I have a problem to calculate in which position classified a team in the last 10 fixtures cause I have to make 10 queries. To store the league table for every fixture in a database table is another approach, but every time I change a match already played I have to recalculate every fixture from there... Is there a better approach for this problem? Thanks

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  • Determining child count of path

    - by sqlnewbie
    I have a table whose 'path' column has values and I would like to update the table's 'child_count' column so that I get the following output. path | child_count --------+------------- | 5 /a | 3 /a/a | 0 /a/b | 1 /a/b/c | 0 /b | 0 My present solution - which is way too inefficient - uses a stored procedure as follows: CREATE FUNCTION child_count() RETURNS VOID AS $$ DECLARE parent VARCHAR; BEGIN FOR parent IN SELECT path FROM my_table LOOP DECLARE tokens VARCHAR[] := REGEXP_SPLIT_TO_ARRAY(parent, '/'); str VARCHAR := ''; BEGIN FOR i IN 2..ARRAY_LENGTH(tokens, 1) LOOP UPDATE my_table SET child_count = child_count + 1 WHERE path = str; str := str || '/' || tokens[i]; END LOOP; END; END LOOP; END; $$ LANGUAGE plpgsql; Anyone knows of a single UPDATE statement that does the same thing?

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  • Inserting data into a Database

    - by Erebus
    SO I'm making a "basic" login file where a person logs in and the data that person entered on that form gets transfered to another form aka my database/table. I think the problems is here but I'll post the rest of the code. CREATE FUNCTION dbo.Function4 ( parameter1 int = 5, parameter2 datatype ) RETURNS Table1 TABLE (UserName, Password, Password_Confirmation, Assets) AS BEGIN INSERT INTO Table1 (UserName, Password, Password_Confirmation, Assets) VALUES (a,b,c,d); /*SELECT ... FROM ...*/ RETURN END This is the Login Form using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace Login_Basic { public partial class Form2 : Form { public Form2() { InitializeComponent(); } Form3 Delta = new Form3(); private void label3_Click(object sender, EventArgs e) { } private void Form2_Load(object sender, EventArgs e) { this.Hide(); } private void textBox6_TextChanged(object sender, EventArgs e) { } private void textBox6_KeyPress(object sender, KeyPressEventArgs e) { int i = Convert.ToInt32(e.KeyChar); if (!(Char.IsDigit(e.KeyChar) || Char.IsControl(e.KeyChar) || (e.KeyChar == '.' && this.Text.Contains(".") == false))) e.Handled = true; } private void button1_Click(object sender, EventArgs e) { Delta.Show(); //if (textBox3.Text.Equals("")) //{ // MessageBox.Show("Please enter your username"); //} //else //{ // this.Hide(); //} // if (textBox4.Text.Equals("")) //{ // MessageBox.Show("Please enter your password"); // } // else //{ // this.Hide(); // } // if (textBox5.Text.Equals("")) // { // MessageBox.Show("Please re-enter your password"); // } // else // { // this.Hide(); // } //if (textBox6.Text.Equals("")) //{ // MessageBox.Show("Please enter your amount"); // // } // else // { // this.Hide(); // } } private void button3_Click(object sender, EventArgs e) { this.Hide(); } private void textBox3_TextChanged(object sender, EventArgs e) { } private void textBox4_TextChanged(object sender, EventArgs e) { } private void textBox5_TextChanged(object sender, EventArgs e) { } private void panel2_Paint(object sender, PaintEventArgs e) { /*if (textBox3.Text.Equals("") && textBox4.Text.Equals("") && textBox5.Text.Equals("") && textBox6.Text.Equals("")) { button1.Enabled = false; } else { button1.Enabled = true; }*/ } } } Here's a "Pic" of my database http://s299.photobucket.com/albums/mm305/krsimms123/Code.jpg Thanks in advance (I'll try and check this every few hours so I can help explain anything)

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  • help with sql query - in access 2007

    - by Gold
    hi i have 2 tables table items has 144602 records table A has 27721 records code in items = BAR8 in A i want to show all records that equal i try this: SELECT Items.Code, A.BAR8 FROM Items INNER JOIN A ON Items.Code = A.BAR8; and i get 28048 records !!! i need to get 27721 , how to do it ? thank's in advance

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  • How to count number of occurences for all different values in database column?

    - by drasto
    I have a Postgre database that has say 10 columns. The fifth column is called column5. There are 100 rows in the database and possible values of column5 are c5value1, c5value2, c5value3...c5value29, c5value30. I would like to print out a table that shows how many times each value occurs. So the table would look like this: Value(of column5) number of occurrences of the value c5value1 1 c5value2 5 c5value3 3 c5value4 9 c5value5 1 c5value6 1 . . . . . . What is the command that does that? Thanks for help

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