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• How to do left joins with least-n-per-group query?

  - by Nate

  I'm trying to get a somewhat complicated query working and am not having any luck whatsoever. Suppose I have the following tables: cart_items: +--------------------------------------------+ | item_id | cart_id | movie_name | quantity | +--------------------------------------------+ | 0 | 0 | braveheart | 4 | | 1 | 0 | braveheart | 9 | | . | . | . | . | | . | . | . | . | | . | . | . | . | | . | . | . | . | +--------------------------------------------+ movies: +------------------------------+ | movie_id | movie_name | ... | +------------------------------+ | 0 | braveheart | . | | . | . | . | | . | . | . | | . | . | . | | . | . | . | +------------------------------+ pricing: +-----------------------------------------+ | id | movie_name | quantity | price_per | +-----------------------------------------+ | 0 | braveheart | 1 | 1.99 | | 1 | braveheart | 2 | 1.50 | | 2 | braveheart | 4 | 1.25 | | 3 | braveheart | 8 | 1.00 | | . | . | . | . | | . | . | . | . | | . | . | . | . | | . | . | . | . | | . | . | . | . | +-----------------------------------------+ I need to join the data from the tables, but with the added complexity that I need to get appropriate price_per from the pricing table. Only one price should be returned for each cart_item, and that should be the lowest price from the pricing table where the quantity for the cart item is at least the quantity in the pricing table. So, the query should return for each item in cart_items the following: +---------------------------------------------+ | item_id | movie_name | quantity | price_per | +---------------------------------------------+ Example 1: Variable passed to the query: cart_id = 0. Return: +---------------------------------------------+ | item_id | movie_name | quantity | price_per | +---------------------------------------------+ | 0 | braveheart | 4 | 1.25 | | 1 | braveheart | 9 | 1.00 | +---------------------------------------------+ Note that this is a minimalist example and that additional data will be pulled from the tables mentioned (particularly the movies table). How could this query be composed? I have tried using left joins and subqueries, but the difficult part is getting the price and nothing I have tried has worked. Thanks for your help. EDIT: I think this is similar to what I have working with my "real" tables: SELECT t1.item_id, t2.movie_name, t1.quantity FROM cart_items t1 LEFT JOIN movies t2 ON t2.movie_name = t1.movie_name WHERE t1.cart_id = 0 Assuming I wrote that correctly (I quickly tried to "port over" my real query), then the output would currently be: +---------------------------------+ | item_id | movie_name | quantity | +---------------------------------+ | 0 | braveheart | 4 | | 1 | braveheart | 9 | +---------------------------------+ The trouble I'm having is joining the price at a certain quantity for a movie. I simply cannot figure out how to do it.

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• How can I remove this query from within a loop?

  - by Chris

  I am currently designing a forum as a personal project. One of the recurring issues I've come across is database queries in loops. I've managed to avoid doing that so far by using table joins or caching of data in arrays for later use. Right now though I've come across a situation where I'm not sure how I can write the code in such a way that I can use either of those methods easily. However I'd still prefer to do at most 2 queries for this operation rather than 1 + 1 per group of forums, which so far has resulted in 5 per page. So while 5 isn't a huge number (though it will increase for each forum group I add) it's the principle that's important to me here, I do NOT want to write queries in loops What I'm doing is displaying forum index groupings (eg admin forums, user forums etc) and then each forum within that group on a single page index, it's the combination of both in one page that's causing me issue. If it had just been a single group per page, I'd use a table join and problem solved. But if I use a table join here, although I can potentially get all the data I need it'll be in one mass of results and it needs displaying properly. Here's the code (I've removed some of the html for clarity) <?php $sql= "select * from forum_groups"; //query 1 $result1 = $database->query($sql); while($group = mysql_fetch_assoc($result1)) //first loop {?> <table class="threads"> <tr> <td class="forumgroupheader"> <?php echo $group['group_name']; ?> </td> </tr> <tr> <td class="forumgroupheader2"> <?php echo $group['group_desc']; ?> </td> </tr> </table> <table> <tr> <th class="thforum"> Forum Name</th> <th class="thforum"> Forum Decsription</th> <th class="thforum"> Last Post </th> <tr> <?php $group_id = $group['id']; $sql = "SELECT forums.id, forums.forum_group_id, forums.forum_name, forums.forum_desc, forums.visible_rank, forums.locked, forums.lock_rank, forums.topics, forums.posts, forums.last_post, forums.last_post_id, users.username FROM forums LEFT JOIN users on forums.last_post_id=users.id WHERE forum_group_id='{$group_id}'"; //query 2 $result2 = $database->query($sql); while($forum = mysql_fetch_assoc($result2)) //second loop {?> So how can I either a) write the SQL in such a way as to remove the second query from inside the loop or b) combine the results in an array either way I need to be able to access the data as an when so I can format it properly for the page output, ie within the loops still.

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• SQL code to insert multiple rows in ms-access table

  - by Thierry

  I'm trying to speed up my code and the bottleneck seems to be the individual insert statements to a Jet MDB from outside Access via ODBC. I need to insert 100 rows at a time and have to repeat that many times. It is possible to insert multiple rows in a table with SQL code? Here is some stuff that I tried but neither of them worked. Any suggestions? INSERT INTO tblSimulation (p, cfYear, cfLocation, Delta, Design, SigmaLoc, Sigma, SampleSize, Intercept) VALUES (0, 2, 8.3, 0, 1, 0.5, 0.2, 220, 3.4), (0, 2.4, 7.8, 0, 1, 0.5, 0.2, 220, 3.4), (0, 2.3, 5.9, 0, 1, 0.5, 0.2, 220, 3.4) INSERT INTO tblSimulation (p, cfYear, cfLocation, Delta, Design, SigmaLoc, Sigma, SampleSize, Intercept) VALUES (0, 2, 8.3, 0, 1, 0.5, 0.2, 220, 3.4) UNION (0, 2.4, 7.8, 0, 1, 0.5, 0.2, 220, 3.4) UNION (0, 2.3, 5.9, 0, 1, 0.5, 0.2, 220, 3.4)

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• Insert element into a tree from a list in Standard ML

  - by vichet

  I have just started to learn SML on my own and get stuck with a question from the tutorial. Let say I have: tree data type datatype node of (tree*int*tree) | null insert function fun insert (newItem, null) = node (null, newItem, null) | insert (newItem, node (left, oldItem, right)) = if (newItem <= oldItem) then node (insert(newItem,left),oldItem, right) else node (left, oldItem, insert(newItem, right) an integer list val intList = [19,23,21,100,2]; my question is how can I add write a function to loop through each element in the list and add to a tree? Your answer is really appreciated.

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• Sql Server - INSERT INTO SELECT to avoid duplicates

  - by Ashish Gupta

  I have following two tables:- Table1 ------------- ID Name 1 A 2 B 3 C Table2 -------- ID Name 1 Z I need to insert data from Table1 to Table2 and I can use following sytax for the same:- INSERT INTO Table2(Id, Name) SELECT Id, Name FROM Table1 However, In my case duplicate Ids might exist in Table2 (In my case Its Just "1") and I dont want to copy that again as that would throw an error. I can write something like this:- IF NOT EXISTS(SELECT 1 FROM Table2 WHERE Id=1) INSERT INTO Table2 (Id, name) SELECT Id, name FROM Table1 ELSE INSERT INTO Table2 (Id, name) SELECT Id, name FROM Table1 WHERE Table1.Id<>1 Is there a better way to do this without using IF - ELSE? I want to avoid two INSERT INTO-SELECT statements based on some condition. Any help is appreciated.

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• IIS URL Rewrite Module Query String Parameters

  - by binarycoder

  Is it possible to use URL Rewrite to provide more complex query string functionality than the "Append query string" checkbox that it has? Specifically, is it possible to specify the keys for certain query string parameters and have it only append those name value pairs. For example, for the input: http://www.example.org/test?alpha=1&beta=2&gamma=3 and the list of query string parameter keys: beta gamma it should output: http://www.example.org/redirect?beta=2&gamma=3 (Note that the query string parameters in the input appear in arbitrary order.)

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• MySQL Insert not working with Date column

  - by Ian McCullough

  Hello All, I am having an issue with a simple insert query into a table. I have this PHP Code $T_MEMBER = "INSERT INTO T_MEMBER (MEMBER_IDENTIFIER,LAST_NAME,FIRST_NAME,BIRTH_DATE) VALUES ('$memberID','$last','$first','$birthdate')"; mysql_query($T_MEMBER) or die(mysql_error()); Here are a few examples of what the query looks like if i echo it: INSERT INTO T_MEMBER (MEMBER_IDENTIFIER,LAST_NAME,FIRST_NAME,BIRTH_DATE) VALUES ('2007','Hayes','Karin','1958-30-10') INSERT INTO T_MEMBER (MEMBER_IDENTIFIER,LAST_NAME,FIRST_NAME,BIRTH_DATE) VALUES ('2020','Long','Peggy','1968-29-5') INSERT INTO T_MEMBER (MEMBER_IDENTIFIER,LAST_NAME,FIRST_NAME,BIRTH_DATE) VALUES ('2021','Torres','Diane','1968-30-8') BIRTH_DATE is a date type column. The problem is, after i do any of these queries, the date shows up as 000-00-00!!!! I have been wracking my brain and i cannot seem to find the issue. Thanks, Ian

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• value of type 'string' cannot be converted to 'Devart.data.postgresql.PgSqlParameter'

  - by hector

  The following is my PostgreSQL table structure and the vb.net code to insert into the tables.Using Devart's Component For PostgreSQL Connect table gtab83 CREATE TABLE gtab83 ( orderid integer NOT NULL DEFAULT nextval('seq_gtab83_id'::regclass), acid integer, slno integer, orderdte date ) table gtab84 CREATE TABLE gtab84 ( orderdetid integer DEFAULT nextval('seq_gtab84_id'::regclass), productid integer, qty integer, orderid integer ) Code to insert into the above tables is below '1.)INSERT INTO gtab83(orderid,acid, slno, orderdte) VALUES (?, ?, ?); '2.)INSERT INTO gtab84(orderdetid,productid, qty, orderid) VALUES (?, ?, ?); Try Dim cmd As PgSqlCommand = New PgSqlCommand("", Myconnstr) cmd.CommandText = _ "INSERT INTO GTAB83(ACID,SLNO,ORDERDTE)" & _ "VALUES " & _ "(@acid,@slno,@orderdte);" Dim paramAcid As PgSqlParameter = New PgSqlParameter("@acid", PgSqlType.Int, 0) Dim paramSlno As PgSqlParameter = New PgSqlParameter("@slno", PgSqlType.Int, 0) Dim paramOrderdte As PgSqlParameter = New PgSqlParameter("@orderdte", PgSqlType.Date, 0) paramAcid = cboCust.SelectedValue paramSlno = txtOrderNO.Text #ERROR# paramOrderdte = (txtDate.Text, "yyyy-MM-dd") #ERROR# Catch ex As Exception End Try ERROR : value of type 'string' cannot be converted to 'Devart.data.postgresql.PgSqlParameter'

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• How to change Zend_Db_Table name within a Model to insert in multiple tables

  - by jwhat

  Using Zend Framework, I've created a Model to insert a record into a database. My question is, after $this->insert($data) how can I switch the active table so that I can insert a record into another table? Here's my code so far: class Model_DbTable_Foo extends Zend_Db_Table_Abstract { protected $_name = 'foo'; public function addFoo($params) { $data = array( 'foo' => $params['foo'], ); $this->insert($data); $foo_id = $this->getAdapter()->lastInsertId(); $data2 = array( 'bar' => $params['bar'] ); // I need to change the Db Table name here. $this->insert($data2); $bar_id = $this->getAdapter()->lastInsertId(); } }

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• MySQL: Is it faster to use inserts and updates instead of insert on duplicate key update?

  - by Nir

  I have a cron job that updates a large number of rows in a database. Some of the rows are new and therefore inserted and some are updates of existing ones and therefore update. I use insert on duplicate key update for the whole data and get it done in one call. But- I actually know which rows are new and which are updated so I can also do inserts and updates seperately. Will seperating the inserts and updates have advantage in terms of performance? What are the mechanics behind this ? Thanks!

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• How Serializable works with insert in SQL Server 2005

  - by Spence

  G'day I think I have a misunderstanding of serializable. I have two tables (data, transaction) which I insert information into in a serializable transaction (either they are both in, or both out, but not in limbo). SET TRANSACTION ISOLATION LEVEL SERIALIZABLE BEGIN TRANSACTION INSERT INTO dbo.data (ID, data) VALUES (@Id, data) INSERT INTO dbo.transactions(ID, info) VALUES (@ID, @info) COMMIT TRANSACTION I have a reconcile query which checks the data table for entries where there is no transaction at read committed isolation level. INSERT INTO reconciles (ReconcileID, DataID) SELECT Reconcile = @ReconcileID, ID FROM Data WHERE NOT EXISTS (SELECT 1 FROM TRANSACTIONS WHERE data.id = transactions.id) Note that the ID is actually a composite (2 column) key, so I can't use a NOT IN operator My understanding was that the second query would exclude any values written into data without their transaction as this insert was happening at serializable and the read was occurring at read committed. I have evidence that reconcile is picking up entries

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• INSERT SELECT Statement and Rollback SQL

  - by Juan Perez

  Im Working on a creation of a query who uses INSERT SELECT statement using MS SQL Server 2008: INSERT INTO TABLE1 (col1, col2) SELECT col1, col2 FROM TABLE2 Right now the excecution of this query is inside a transaction: Pseudocode: try { begin transaction; query; commit; } catch { rollback; } If TABLE2 has around 40m of rows, at the moment of making the insert on the TABLE1, if there is an error in the middle of the INSERT, will the INSERT SELECT statement make a rollback itself or I need to use a transaction to preserve data integrity? It is necessary to use a transaction? or SQL SERVER it self uses a transaction for this type of sentences.

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• how to choose which row to insert with same id in sql?

  - by user1429595

  so Basically I have a table called "table_1" : ID Index STATUS TIME DESCRIPTION 1 15 pending 1:00 Started Pending 1 16 pending 1:05 still in request 1 17 pending 1:10 still in request 1 18 complete 1:20 Transaction has been completed 2 19 pending 2:25 request has been started 2 20 pending 2:30 in progress 2 21 pending 2:35 in progess still 2 22 pending 2:40 still pending 2 23 complete 2:45 Transaction Compeleted I need to insert these data into my second table "table_2" where only start and compelete times are included, so my "table_2" should like this: ID Index STATUS TIME DESCRIPTION 1 15 pending 1:00 Started Pending 1 18 complete 1:20 Transaction has been completed 2 19 pending 2:25 request has been started 2 23 complete 2:45 Transaction Compeleted if anyone can help me write sql query for this I would highly appreciate it. Thanks in advance

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• Mistake in display and insert methods (double-ended queue)

  - by MANAL

  1) My problem when i make remove from right or left program will be remove true but when i call diplay method the content wrong like this I insert 12 43 65 23 and when make remove from left program will remove 12 but when call display method show like this 12 43 65 and when make remove from right program will remove 23 but when call display method show like this 12 43 Why ?????? ); and when i try to make insert after remove write this Can not insert right because the queue is full . first remove right and then u can insert right where is the problem ?? Please Help me please 2) My code FIRST CLASS class dqueue { private int fullsize; //number of all cells private int item_num; // number of busy cells only private int front,rear; public int j; private double [] dqarr; //========================================== public dqueue(int s) //constructor { fullsize = s; front = 0; rear = -1; item_num = 0; dqarr = new double[fullsize]; } //========================================== public void insert(double data) { if (rear == fullsize-1) rear = -1; rear++; dqarr[rear] = data; item_num++; } public double removeLeft() // take item from front of queue { double temp = dqarr[front++]; // get value and incr front if(front == fullsize) front = 0; item_num --; // one less item return temp; } public double removeRight() // take item from rear of queue { double temp = dqarr[rear--]; // get value and decr rear if(rear == -1) // rear = item_num -1; item_num --; // one less item return temp; } //========================================= public void display () //display items { for (int j=0;j<item_num;j++) // for every element System.out.print(dqarr[j] +" " ); // display it System.out.println(""); } //========================================= public int size() //number of items in queue { return item_num; } //========================================== public boolean isEmpty() // true if queue is empty { return (item_num ==0); } } SECOND CLASS import java.util.Scanner; class dqueuetest { public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println(" ***** Welcome here***** "); System.out.println(" ***** Mind Of Programming Group***** "); System.out.println(" _____________________________________________ "); System.out.println("enter size of your dqueue"); int size = input.nextInt(); dqueue mydq = new dqueue(size); System.out.println(""); System.out.println("enter your itemes"); //===================================== for(int i = 0;i<=size-1;i++) { System.out.printf("item %d:",i+1); double item = input.nextDouble(); mydq.insert(item); System.out.println(""); } //===================================== int queue =size ; int c = 0 ; while (c != 6) { System.out.println(""); System.out.println("************************************************"); System.out.println(" MAIN MENUE"); System.out.println("1- INSERT RIGHT "); System.out.println("2- REMOVE LEFT"); System.out.println("3- REMOVE RIGHT"); System.out.println("4- DISPLAY"); System.out.println("5- SIZE"); System.out.println("6- EXIT"); System.out.println("************************************************"); System.out.println("choose your operation by number(1-6)"); c = input.nextInt(); switch (c) { case 1: if (queue == size) System.out.print("Can not insert right because the queue is full . first remove right and then u can insert right "); else { System.out.print("enter your item: "); double item = input.nextDouble(); mydq.insert(item);} break; case 2: System.out.println("REMOVE FROM REAR :"); if( !mydq.isEmpty() ) { double item = mydq.removeLeft(); System.out.print(item + "\t"); } // end while System.out.println(""); mydq.display(); break; case 3: System.out.println("REMOVE FROM FRONT :"); if( !mydq.isEmpty() ) { double item = mydq.removeRight(); System.out.print(item + "\t"); } // end while System.out.println(""); mydq.display(); break; case 4: System.out.println("The items in Queue are :"); mydq.display(); break; case 5: System.out.println("The Size of the Queue is :"+mydq.size()); break; case 6: System.out.println("Good Bye"); break; default: System.out.println("wrong chiose enter again"); } //end switch } //end while } // end main }//end class

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• Repeating characters in VIM insert mode

  - by Cthutu

  Is there a way of repeating a character while in Vim's insert mode? For example, say I would like to insert 80 dashes, in something like emacs I would type: Ctrl+U 8 0 - The only way I know how to do it in VIM is to exit normal mode for the repeat argument, then go back into insert mode to type the dash, then exit to insert the actual dashes, AND then go back into insert mode to carry on typing. The sequence is a really long: <ESC> 8 0 a - <ESC> a It would be nice not to switch in and out of modes. Thanks

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• Insert into select and update in single query

  - by Ossi

  I have 4 tables: tempTBL, linksTBL and categoryTBL, extra on my tempTBL I have: ID, name, url, cat, isinserted columns on my linksTBL I have: ID, name, alias columns on my categoryTBL I have: cl_id, link_id,cat_id on my extraTBL I have: id, link_id, value How do I do a single query to select from tempTBL all items where isinsrted = 0 then insert them to linksTBL and for each record inserted, pickup ID (which is primary) and then insert that ID to categoryTBL with cat_id = 88. after that insert extraTBL ID for link_id and url for value. I know this is so confusing, put I'll post this anyhow... This is what I have so far: INSERT IGNORE INTO linksTBL (link_id,link_name,alias) VALUES(NULL,'tex2','hello'); # generate ID by inserting NULL INSERT INTO categoryTBL (link_id,cat_id) VALUES(LAST_INSERT_ID(),'88'); # use ID in second table I would like to add here somewhere that it only selects items where isinserted = 0 and iserts those records, and onse inserted, will change isinserted to 1, so when next time it runs, it will not add them again.

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• Can't INSERT INTO SELECT into a table with identity column

  - by Eran Goldin

  In SQL server, I'm using a table variable and when done manipulating it I want to insert its values into a real table that has an identity column which is also the PK. The table variable I'm making has two columns; the physical table has four, the first of which is the identity column, an integer IK. The data types for the columns I want to insert are the same as the target columns' data types. INSERT INTO [dbo].[Message] ([Name], [Type]) SELECT DISTINCT [Code],[MessageType] FROM @TempTableVariable END This fails with Cannot insert duplicate key row in object 'dbo.Message' with unique index 'IX_Message_Id'. The duplicate key value is (ApplicationSelection). But when trying to insert just Values (...) it works ok. How do I get it right?

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• Mistake in dispaly and insert method (double - ended queue)

  - by MANAL

  1) My problem when i make remove from right or left program will be remove true but when i call diplay method the content wrong like this I insert 12 43 65 23 and when make remove from left program will remove 12 but when call display method show like this 12 43 65 and when make remove from right program will remove 23 but when call display method show like this 12 43 Why ?????? ); and when i try to make insert after remove write this Can not insert right because the queue is full . first remove right and then u can insert right where is the problem ?? Please Help me please 2) My code FIRST CLASS class dqueue { private int fullsize; //number of all cells private int item_num; // number of busy cells only private int front,rear; public int j; private double [] dqarr; //========================================== public dqueue(int s) //constructor { fullsize = s; front = 0; rear = -1; item_num = 0; dqarr = new double[fullsize]; } //========================================== public void insert(double data) { if (rear == fullsize-1) rear = -1; rear++; dqarr[rear] = data; item_num++; } public double removeLeft() // take item from front of queue { double temp = dqarr[front++]; // get value and incr front if(front == fullsize) front = 0; item_num --; // one less item return temp; } public double removeRight() // take item from rear of queue { double temp = dqarr[rear--]; // get value and decr rear if(rear == -1) // rear = item_num -1; item_num --; // one less item return temp; } //========================================= public void display () //display items { for (int j=0;j //========================================= public int size() //number of items in queue { return item_num; } //========================================== public boolean isEmpty() // true if queue is empty { return (item_num ==0); } } SECOND CLASS import java.util.Scanner; class dqueuetest { public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println(" Welcome here** "); System.out.println(" * Mind Of Programming Group*** "); System.out.println(" _________________________ "); System.out.println("enter size of your dqueue"); int size = input.nextInt(); dqueue mydq = new dqueue(size); System.out.println(""); System.out.println("enter your itemes"); //===================================== for(int i = 0;i<=size-1;i++) { System.out.printf("item %d:",i+1); double item = input.nextDouble(); mydq.insert(item); System.out.println(""); } //===================================== int queue =size ; int c = 0 ; while (c != 6) { System.out.println(""); System.out.println("**************************"); System.out.println(" MAIN MENUE"); System.out.println("1- INSERT RIGHT "); System.out.println("2- REMOVE LEFT"); System.out.println("3- REMOVE RIGHT"); System.out.println("4- DISPLAY"); System.out.println("5- SIZE"); System.out.println("6- EXIT"); System.out.println("**************************"); System.out.println("choose your operation by number(1-6)"); c = input.nextInt(); switch (c) { case 1: if (queue == size) System.out.print("Can not insert right because the queue is full . first remove right and then u can insert right "); else { System.out.print("enter your item: "); double item = input.nextDouble(); mydq.insert(item);} break; case 2: System.out.println("REMOVE FROM REAR :"); if( !mydq.isEmpty() ) { double item = mydq.removeLeft(); System.out.print(item + "\t"); } // end while System.out.println(""); mydq.display(); break; case 3: System.out.println("REMOVE FROM FRONT :"); if( !mydq.isEmpty() ) { double item = mydq.removeRight(); System.out.print(item + "\t"); } // end while System.out.println(""); mydq.display(); break; case 4: System.out.println("The items in Queue are :"); mydq.display(); break; case 5: System.out.println("The Size of the Queue is :"+mydq.size()); break; case 6: System.out.println("Good Bye"); break; default: System.out.println("wrong chiose enter again"); } //end switch } //end while } // end main }//end class

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• Last element not getting insert in Tree

  - by rdk1992

  So I was asked to make a Binary Tree in Haskell taking as input a list of Integers. Below is my code. My problem is that the last element of the list is not getting inserted in the Tree. For example [1,2,3,4] it only inserts to the tree until "3" and 4 is not inserted in the Tree. data ArbolBinario a = Node a (ArbolBinario a) (ArbolBinario a) | EmptyNode deriving(Show) insert(x) EmptyNode= insert(tail x) (Node (head x) EmptyNode EmptyNode) insert(x) (Node e izq der) |x == [] = EmptyNode --I added this line to fix the Prelude.Head Empty List error, after I added this line the last element started to be ignored and not inserted in the tree |head x == e = (Node e izq der) |head x < e = (Node e (insert x izq) der) |head x > e = (Node e izq (insert x der)) Any ideas on whats going on here? Help is much appreciated

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• SQL SERVER – DMV – sys.dm_os_wait_stats Explanation – Wait Type – Day 3 of 28

  - by pinaldave

  The key Dynamic Management View (DMV) that helps us to understand wait stats is sys.dm_os_wait_stats; this DMV gives us all the information that we need to know regarding wait stats. However, the interpretation is left to us. This is a challenge as understanding wait stats can often be quite tricky. Anyway, we will cover few wait stats in one of the future articles. Today we will go over the basic understanding of the DMV. The Official Book OnLine Reference for DMV is over here: sys.dm_os_wait_stats. I suggest you all to refer this for all the accuracy. Following is a statement from the online book: “Specific types of wait times during query execution can indicate bottlenecks or stall points within the query. Similarly, high wait times, or wait counts server wide can indicate bottlenecks or hot spots in interaction query interactions within the server instance.” This is the statement which has inspired me to write this series. Let us first run the following statement from DMV. SELECT * FROM sys.dm_os_wait_stats ORDER BY wait_time_ms DESC GO Above statement will show us few of the columns. Here it is quick explanation of each of the column. wait_type – this is the name of the wait type. There can be three different kinds of wait types – resource, queue and external. waiting_tasks_count – this incremental counter is a good indication of frequent the wait is happening. If this number is very high, it is good indication for us to investigate that particular wait type. It is quite possible that the wait time is considerably low, but the frequency of the wait is much high. wait_time_ms – this is total wait accumulated for any type of wait. This is the total wait time and includes singal_wait_time_ms. max_wait_time_ms – this indicates the maximum wait type ever occurred for that particular wait type. Using this, one can estimate the intensity of the wait type in past. Again, it is not necessary that this max wait time will occur every time; so do not over invest yourself here. signal_wait_time_ms – this is the wait time when thread is marked as runnable and it gets to the running state. If the runnable queue is very long, you will find that this wait time becomes high. Additionally, please note that this DMV does not show current wait type or wait stats. This is cumulative view of the all the wait stats since server (instance) restarted or wait stats have been cleared. In future blog post, we will also cover two more DMVs which can be helpful to identify wait-related issues. ?sys.dm_os_waiting_tasks sys.dm_exec_requests Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL DMV, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• SQL SERVER – Updating Data in A Columnstore Index

  - by pinaldave

  So far I have written two articles on Columnstore Indexes, and both of them got very interesting readership. In fact, just recently I got a query on my previous article on Columnstore Index. Read the following two articles to get familiar with the Columnstore Index. They will give you a reference to the question which was asked by a certain reader: SQL SERVER – Fundamentals of Columnstore Index SQL SERVER – How to Ignore Columnstore Index Usage in Query Here is the reader’s question: ” When I tried to update my table after creating the Columnstore index, it gives me an error. What should I do?” When the Columnstore index is created on the table, the table becomes Read-Only table and it does not let any insert/update/delete on the table. The basic understanding is that Columnstore Index will be created on the table that is very huge and holds lots of data. If a table is small enough, there is no need to create a Columnstore index. The regular index should just help it. The reason why Columnstore index was needed is because the table was so big that retrieving the data was taking a really, really long time. Now, updating such a huge table is always a challenge by itself. If the Columnstore Index is created on the table, and the table needs to be updated, you need to know that there are various ways to update it. The easiest way is to disable the Index and enable it. Consider the following code: USE AdventureWorks GO -- Create New Table CREATE TABLE [dbo].[MySalesOrderDetail]( [SalesOrderID] [int] NOT NULL, [SalesOrderDetailID] [int] NOT NULL, [CarrierTrackingNumber] [nvarchar](25) NULL, [OrderQty] [smallint] NOT NULL, [ProductID] [int] NOT NULL, [SpecialOfferID] [int] NOT NULL, [UnitPrice] [money] NOT NULL, [UnitPriceDiscount] [money] NOT NULL, [LineTotal] [numeric](38, 6) NOT NULL, [rowguid] [uniqueidentifier] NOT NULL, [ModifiedDate] [datetime] NOT NULL ) ON [PRIMARY] GO -- Create clustered index CREATE CLUSTERED INDEX [CL_MySalesOrderDetail] ON [dbo].[MySalesOrderDetail] ( [SalesOrderDetailID]) GO -- Create Sample Data Table -- WARNING: This Query may run upto 2-10 minutes based on your systems resources INSERT INTO [dbo].[MySalesOrderDetail] SELECT S1.* FROM Sales.SalesOrderDetail S1 GO 100 -- Create ColumnStore Index CREATE NONCLUSTERED COLUMNSTORE INDEX [IX_MySalesOrderDetail_ColumnStore] ON [MySalesOrderDetail] (UnitPrice, OrderQty, ProductID) GO -- Attempt to Update the table UPDATE [dbo].[MySalesOrderDetail] SET OrderQty = OrderQty +1 WHERE [SalesOrderID] = 43659 GO /* It will throw following error Msg 35330, Level 15, State 1, Line 2 UPDATE statement failed because data cannot be updated in a table with a columnstore index. Consider disabling the columnstore index before issuing the UPDATE statement, then rebuilding the columnstore index after UPDATE is complete. */ A similar error also shows up for Insert/Delete function. Here is the workaround. Disable the Columnstore Index and performance update, enable the Columnstore Index: -- Disable the Columnstore Index ALTER INDEX [IX_MySalesOrderDetail_ColumnStore] ON [dbo].[MySalesOrderDetail] DISABLE GO -- Attempt to Update the table UPDATE [dbo].[MySalesOrderDetail] SET OrderQty = OrderQty +1 WHERE [SalesOrderID] = 43659 GO -- Rebuild the Columnstore Index ALTER INDEX [IX_MySalesOrderDetail_ColumnStore] ON [dbo].[MySalesOrderDetail] REBUILD GO This time it will not throw an error while the update of the table goes successfully. Let us do a cleanup of our tables using this code: -- Cleanup DROP INDEX [IX_MySalesOrderDetail_ColumnStore] ON [dbo].[MySalesOrderDetail] GO TRUNCATE TABLE dbo.MySalesOrderDetail GO DROP TABLE dbo.MySalesOrderDetail GO In the next post we will see how we can use Partition to update the Columnstore Index. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Index, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – A Puzzle Part 4 – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value

  - by pinaldave

  It seems like every weekend I get a new puzzle in my mind. Before continuing I suggest you read my previous posts here where I have shared earlier puzzles. A Puzzle – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value  A Puzzle Part 2 – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value A Puzzle Part 3 – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value After reading above three posts, I am very confident that you all will be ready for the next set of puzzles now. First execute the script which I have written here. Now guess what will be the next value as requested in the query. USE TempDB GO -- Create sequence CREATE SEQUENCE dbo.SequenceID AS DECIMAL(3,0) START WITH 1 INCREMENT BY -1 MINVALUE 1 MAXVALUE 3 CYCLE NO CACHE; GO SELECT next value FOR dbo.SequenceID; -- Guess the number SELECT next value FOR dbo.SequenceID; -- Clean up DROP SEQUENCE dbo.SequenceID; GO Please note that Starting value is 1, Increment value is the negative value of -1 and Minimum value is 3. Now let us first assume how this will work out. In our example of the sequence starting value is equal to 1 and decrement value is -1, this means the value should decrement from 1 to 0. However, the minimum value is 1. This means the value cannot further decrement at all. What will happen here? The natural assumption is that it should throw an error. How many of you are assuming about query will throw an ERROR? Well, you are WRONG! Do not blame yourself, it is my fault as I have told you only half of the story. Now if you have voted for error, let us continue running above code in SQL Server Management Studio. The above script will give the following output: Isn’t it interesting that instead of error out it is giving us result value 3. To understand the answer about the same, carefully observe the original syntax of creating SEQUENCE – there is a keyword CYCLE. This keyword cycles the values between the minimum and maximum value and when one of the range is exhausted it cycles the values from the other end of the cycle. As we have negative incremental value when query reaches to the minimum value or lower end it will cycle it from the maximum value. Here the maximum value is 3 so the next logical value is 3. If your business requirement is such that if sequence reaches the maximum or minimum value, it should throw an error, you should not use the keyword cycle, and it will behave as discussed. I hope, you are enjoying the puzzles as much as I am enjoying it. If you have any interesting puzzle to share, please do share with me and I will share this on blog with due credit to you. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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• Developer Training – 6 Online Courses to Learn SQL Server, MySQL and Technology

  - by Pinal Dave

  Video courses are the next big thing and I am so happy that I have so far authored 6 different video courses with Pluralsight. Here is the list of the courses. I have listed all of my video courses over here. Note: If you click on the courses and it does not open, you need to login to Pluralsight with a valid username and password or sign up for a FREE trial. Please leave a comment with your favorite course in the comment section. Random 10 winners will get surprise gift via email. Bonus: If you list your favorite module from the course site. SQL Server Performance: Introduction to Query Tuning SQL Server performance tuning is an in-depth topic, and an art to master. A key component of overall application performance tuning is query tuning. Writing queries in an efficient manner, and making sure they execute in the most optimal way possible, is always a challenge. The basics revolve around the details of how SQL Server carries out query execution, so the optimizations explored in this course follow along the same lines. Click to View Course SQL Server Performance: Indexing Basics Indexes are the most crucial objects of the database. They are the first stop for any DBA and Developer when it is about performance tuning. There is a good side as well evil side of the indexes. To master the art of performance tuning one has to understand the fundamentals of the indexes and the best practices associated with the same. This course is for every DBA and Developer who deals with performance tuning and wants to use indexes to improve the performance of the server. Click to View Course SQL Server Questions and Answers This course is designed to help you better understand how to use SQL Server effectively. The course presents many of the common misconceptions about SQL Server, and then carefully debunks those misconceptions with clear explanations and short but compelling demos, showing you how SQL Server really works. This course is for anyone working with SQL Server databases who wants to improve her knowledge and understanding of this complex platform. Click to View Course MySQL Fundamentals MySQL is a popular choice of database for use in web applications, and is a central component of the widely used LAMP open source web application software stack. This course covers the fundamentals of MySQL, including how to install MySQL as well as written basic data retrieval and data modification queries. Click to View Course Building a Successful Blog Expressing yourself is the most common behavior of humans. Blogging has made easy to express yourself. Just like a letter or book has a structure and formula, blogging also has structure and formula. In this introductory course on blogging we will go over a few of the basics of blogging and show the way to get started with blogging immediately. If you already have a blog, this course will be even more relevant as this will discuss many of the common questions and issue you face in your blogging routine. Click to View Course Introduction to ColdFusion ColdFusion is rapid web application development platform. In this course you will learn the basics of how to use ColdFusion platform and rapidly develop web sites. The course begins with learning basics of ColdFusion Markup Language and moves to common development language practices. From there we move to frequent database operations and advanced concepts of Forms, Sessions and Cookies. The last module sums up all the concepts covered in the course with sample application. Click to View Course Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Training, T SQL, Technology

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• SQL SERVER – Puzzle #1 – Querying Pattern Ranges and Wild Cards

  - by Pinal Dave

  Note: Read at the end of the blog post how you can get five Joes 2 Pros Book #1 and a surprise gift. I have been blogging for almost 7 years and every other day I receive questions about Querying Pattern Ranges. The most common way to solve the problem is to use Wild Cards. However, not everyone knows how to use wild card properly. SQL Queries 2012 Joes 2 Pros Volume 1 – The SQL Queries 2012 Hands-On Tutorial for Beginners Book On Amazon | Book On Flipkart Learn SQL Server get all the five parts combo kit Kit on Amazon | Kit on Flipkart Many people know wildcards are great for finding patterns in character data. There are also some special sequences with wildcards that can give you even more power. This series from SQL Queries 2012 Joes 2 Pros® Volume 1 will show you some of these cool tricks. All supporting files are available with a free download from the www.Joes2Pros.com web site. This example is from the SQL 2012 series Volume 1 in the file SQLQueries2012Vol1Chapter2.2Setup.sql. If you need help setting up then look in the “Free Videos” section on Joes2Pros under “Getting Started” called “How to install your labs” Querying Pattern Ranges The % wildcard character represents any number of characters of any length. Let’s find all first names that end in the letter ‘A’. By using the percentage ‘%’ sign with the letter ‘A’, we achieve this goal using the code sample below: SELECT * FROM Employee WHERE FirstName LIKE '%A' To find all FirstName values beginning with the letters ‘A’ or ‘B’ we can use two predicates in our WHERE clause, by separating them with the OR statement. Finding names beginning with an ‘A’ or ‘B’ is easy and this works fine until we want a larger range of letters as in the example below for ‘A’ thru ‘K’: SELECT * FROM Employee WHERE FirstName LIKE 'A%' OR FirstName LIKE 'B%' OR FirstName LIKE 'C%' OR FirstName LIKE 'D%' OR FirstName LIKE 'E%' OR FirstName LIKE 'F%' OR FirstName LIKE 'G%' OR FirstName LIKE 'H%' OR FirstName LIKE 'I%' OR FirstName LIKE 'J%' OR FirstName LIKE 'K%' The previous query does find FirstName values beginning with the letters ‘A’ thru ‘K’. However, when a query requires a large range of letters, the LIKE operator has an even better option. Since the first letter of the FirstName field can be ‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘F’, ‘G’, ‘H’, ‘I’, ‘J’ or ‘K’, simply list all these choices inside a set of square brackets followed by the ‘%’ wildcard, as in the example below: SELECT * FROM Employee WHERE FirstName LIKE '[ABCDEFGHIJK]%' A more elegant example of this technique recognizes that all these letters are in a continuous range, so we really only need to list the first and last letter of the range inside the square brackets, followed by the ‘%’ wildcard allowing for any number of characters after the first letter in the range. Note: A predicate that uses a range will not work with the ‘=’ operator (equals sign). It will neither raise an error, nor produce a result set. --Bad query (will not error or return any records) SELECT * FROM Employee WHERE FirstName = '[A-K]%' Question: You want to find all first names that start with the letters A-M in your Customer table and end with the letter Z. Which SQL code would you use? a. SELECT * FROM Customer WHERE FirstName LIKE 'm%z' b. SELECT * FROM Customer WHERE FirstName LIKE 'a-m%z' c. SELECT * FROM Customer WHERE FirstName LIKE 'a-m%z' d. SELECT * FROM Customer WHERE FirstName LIKE '[a-m]%z' e. SELECT * FROM Customer WHERE FirstName LIKE '[a-m]z%' f. SELECT * FROM Customer WHERE FirstName LIKE '[a-m]%z' g. SELECT * FROM Customer WHERE FirstName LIKE '[a-m]z%' Contest Leave a valid answer before June 18, 2013 in the comment section. 5 winners will be selected from all the valid answers and will receive Joes 2 Pros Book #1. 1 Lucky person will get a surprise gift from Joes 2 Pros. The contest is open for all the countries where Amazon ships the book (USA, UK, Canada, India and many others). Special Note: Read all the options before you provide valid answer as there is a small trick hidden in answers. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Joes 2 Pros, PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Sorting: TransientVO Vs Query/EO based VO

  - by Vijay Mohan

  In ADF, you can do a sorting on VO rows by invoking setSortBy("VOAttrName") API, but the tricky part is that, this API actually appends a clause to VO query at runtime and the actual sorting is performed after doing VO.executeQuery(), this goes fine for Query/EO based VO. But, how about the transient VO, wherein the rows are populated programmatically..?There is a way to it..:)you can actually specify the query mode on your transient VO, so that the sorting happens on already populated VO rows.Here are the steps to go about it..//Populate your transient VO rows.//VO.setSortBy("YourVOAttrName");//VO.setQueryMode(ViewObject.QUERY_MODE_SCAN_VIEW_ROWS);//VO.executeQuery();So, here the executeQuery() is actually the trigger which calls for VO rows sorting.QUERY_MODE_SCAN_VIEW_ROWS flag makes sure that the sorting is performed on the already populated VO cache.

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