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• File server share access intermittent/slow/machine unstable: win2kr2

  - by Jack B.

  I have a file server running Win2k8R2 on an older HP DL380G4. It has nothing set up on it other than file sharing. All drivers/firmware/updates installed. The file server is used as a dump for a bunch of test machines - so essentially a lot of small files are being written to it. It was working fine until it started showing the following symptoms: Shares became either very slow/intermittent or could not access them at all. Logging in the the server, you could use it like normal but windows would start freezing and eventually you had to hard reboot it because nothing was responsive. After rebooting, it would work fine for 20min-2hours and then degrade into this broken state again. Some info after investigation: HP Raid Config utility shows the Raid array as functioning properly (RAID5 btw). Event log shows a bunch of DoS attacks from the test machines, saying it has disconnected the connection a. AFAIK (not part of my job) the test machines haven't changed the way they log information to this server or the amount of them hasn't increased. b. Nothing is infected, this server was scanned fully, and the test machines are re-imaged almost daily. Nothing in performance monitor shows as anything being pegged at maximum (CPU/HD/Network/RAM) I installed MS Network Monitor and it is showing a lot of traffic The server was using one gigabit Ethernet connection, I connected the second one as well with the same results. Forgot to add - one of the commonly written to dirs on the share has over 16k subdirs in it, with a crapton of small files within those dirs. Some of the OS instability was slow access to the drive which has this directory - perfmon doesn't show much activity on the HD though so I'm not sure if this crowded dir is the cause. Here is one important fact: I ran into this issue 2-3 months ago, couldn't figure it out, but I had a spare identical machine so I swapped them out (thought it was related to the machine), and now I have the same issue. Also, the computer will be stable if I turn off file sharing. So is the server just getting DoS'd by the test machines? I've never dealt with such an issue. Is instability in the server's OS common when getting DoS'd? Is there anything I can do to confirm this before telling the owners of the test machines to optimize their traffic? (I'm not sure what they'll be able to do). Is there something within Win2k8R2 that can balance the traffic across the two NICs? Any help would be appreciated. Update: Another thought - the drive with the share is RAID5 across 6 SCSI320 300GB HDs. They are near full capacity about 100GB from 1TB left. Could the amount of tiny files could be causing some weirdness with the parity in this array? I think I've read something about this in the past but I'm no expert on RAID.

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• What are the SQL Server query syntax not supported by MySQL?

  - by ANP

  I am working in a project where we are using SQL Server database currently. But recently a decision has been taken that the database will be changed to MySQL. I am not using any stored procedures, views, triggers, user defined functions, etc. But I think even then some queries written for SQL Server will not be supported by MySQL. Can anyone help: what are the things that I have to check (and change) so that all the queries will work properly for MySQL also?

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• SQL SERVER – Create Primary Key with Specific Name when Creating Table

  - by pinaldave

  It is interesting how sometimes the documentation of simple concepts is not available online. I had received email from one of the reader where he has asked how to create Primary key with a specific name when creating the table itself. He said, he knows the method where he can create the table and then apply the primary key with specific name. The attached code was as follows: CREATE TABLE [dbo].[TestTable]( [ID] [int] IDENTITY(1,1) NOT NULL, [FirstName] [varchar](100) NULL) GO ALTER TABLE [dbo].[TestTable] ADD  CONSTRAINT [PK_TestTable] PRIMARY KEY CLUSTERED ([ID] ASC) GO He wanted to know if we can create Primary Key as part of the table name as well, and also give it a name at the same time. Though it would look very normal to all experienced developers, it can be still confusing to many. Here is the quick code that functions as the above code in one single statement. CREATE TABLE [dbo].[TestTable]( [ID] [int] IDENTITY(1,1) NOT NULL, [FirstName] [varchar](100) NULL CONSTRAINT [PK_TestTable] PRIMARY KEY CLUSTERED ([ID] ASC) ) GO Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, Readers Question, SQL, SQL Authority, SQL Constraint and Keys, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – What is Page Life Expectancy (PLE) Counter

  - by pinaldave

  During performance tuning consultation there are plenty of counters and values, I often come across. Today we will quickly talk about Page Life Expectancy counter, which is commonly known as PLE as well. You can find the value of the PLE by running following query. SELECT [object_name], [counter_name], [cntr_value] FROM sys.dm_os_performance_counters WHERE [object_name] LIKE '%Manager%' AND [counter_name] = 'Page life expectancy' The recommended value of the PLE counter is 300 seconds. I have seen on busy system this value to be as low as even 45 seconds and on unused system as high as 1250 seconds. Page Life Expectancy is number of seconds a page will stay in the buffer pool without references. In simple words, if your page stays longer in the buffer pool (area of the memory cache) your PLE is higher, leading to higher performance as every time request comes there are chances it may find its data in the cache itself instead of going to hard drive to read the data. Now check your system and post back what is this counter value for you during various time of the day. Is this counter any way relates to performance issues for your system? Note: There are various other counters which are important to discuss during the performance tuning and this counter is not everything. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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• SQL SERVER – Take the Quiz for a chance to win a Quadcopter Drone – Brain Teasers

  - by Pinal Dave

  It has been a long time since we ran quiz. So let us get ready for a quiz. The quiz has two parts. You have to get both the parts correct to win Quadcopter with Camera (we will call it drone). We will be giving away a total of 2 Quadcopters. The quiz is extremely easy and I will ship the Drone anywhere in the world where Amazon will ship it. Let us jump directly to the quiz. Please complete all the three questions of the contest.  Contest Part 1: Brain Teasers There are two questions for you in this part of the contest. Question: There are two 7s. How will you write select statement with a single operator that returns single 7? Hint: SELECT 7(Answer)7 Question: Write down the shortest code that produces 1 without using any numbers in the select statement? Hint: SELECT (Answer) Contest Part 2: Download and Activate Rapid SQL Question: Download and Activate Rapid SQL. Hint: You have to download and activate Rapid SQL. If you do not activate Rapid SQL, you will be disqualified for the contest. Why take risk, let us start! That’s it! Just answer above questions in the following comments area, in following format. Remember: Use comments area right below the blog to take participation in the contest Answer before June 5, 2014 midnight GMT. The winner will be announced on June 8. The winner will be selected randomly from all the valid answers. All the valid answers will be kept hidden till June 5, 2014. There will be a total of two winners. The contest is open for any country of the world where Amazon ships products. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• SQL SERVER – Demo Script – Keeping CPU Busy

  - by pinaldave

  Recently face very interesting situation, during presentations at event, I was asked very famous questions: “My CPU is very high all the time, how can I reduce it?” This is very interesting question and there are many answers and a single blog post is not good enough to justify this subject. I presented few situation to the person who asked the question. The member of the audience who asked question came to me afterwords and asked me few detailed questions. To answer him, I quickly wrote query which simulate high CPU. Here is the script which I wrote which increased CPU from 10% to 80%. I was wondering if there is any similar script which can simulate high CPU usage. If you have share with me and I will publish with due credit. Here is my script for the same: USE AdventureWorks GO DECLARE @Flag INT SET @Flag = 1 WHILE(@Flag < 1000) BEGIN ALTER INDEX [PK_SalesOrderDetail_SalesOrderID_SalesOrderDetailID] ON [Sales].[SalesOrderDetail] REBUILD SET @Flag = @Flag + 1 END GO   Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• RAID5 over LVM on Ubuntu Server 12.04.3

  - by April Ethereal

  I'm trying to create a RAID5 software array using LVM. I use VirtualBox as I'm only learning how LVM works. So I've created 4 virtual SCSI drives and then did the following: pvcreate /dev/sd[b-e] vgcreate /dev/sd[b-e] raid5_vg lvcreate --type raid5 -i 3 -L 1G -n raid_lv raid5_vg However, I get an error after the last command: WARNING: Unrecognised segment type raid5 Using default stripesize 64.00 KiB Rounding size (256 extents) up to stripe boundary size (258 extents) Cannot update volume group raid5_vg with unknown segments in it! So it looks like raid5 is not a valid segment type. "lvm segtypes" also doesn't contain 'raid5' entry: root@ubuntu-lvm:~# lvm segtypes striped zero error free snapshot mirror So my question is - how could I create RAID5 logical volume using LVM only? It seems that it is possible, I saw a few references (not for Ubuntu, unfortunately) for RedHat and Gentoo systems. I don't want to use mdadm for now, until I find out that it is mandatory. Some info about my system is below: root@ubuntu-lvm:~# uname -a Linux ubuntu-lvm 3.8.0I use Ubuntu Server 12.04.3 (i686)-29-generic #42~precise1-Ubuntu SMP Wed Aug 14 15:31:16 UTC 2013 i686 i686 i386 GNU/Linux root@ubuntu-lvm:~# dpkg -l | grep lvm ii lvm2 2.02.66-4ubuntu7.3 The Linux Logical Volume Manager Thanks.

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• SQL SERVER – Removing Leading Zeros From Column in Table – Part 2

  - by pinaldave

  Earlier I wrote a blog post about Remvoing Leading Zeros from Column In Table. It was a great co-incident that my friend Madhivanan (no need of introduction for him) also post a similar article over on BeyondRelational.com. I strongly suggest to read his blog as well as he has suggested some cool solutions to the same problem. On original blog post asked two questions 1) if my sample for testing is correct and 2) If there is any better method to achieve the same. The response was amazing. I am proud on our SQL Community that we all keep on improving on each other’s contribution. There are some really good suggestions as a comment. Let us go over them right now. Improving the ResultSet I had missed including all zeros in my sample set which was an overlook. Here is the new sample which includes all zero values as well. USE tempdb GO -- Create sample table CREATE TABLE Table1 (Col1 VARCHAR(100)) INSERT INTO Table1 (Col1) SELECT '0001' UNION ALL SELECT '000100' UNION ALL SELECT '100100' UNION ALL SELECT '000 0001' UNION ALL SELECT '00.001' UNION ALL SELECT '01.001' UNION ALL SELECT '0000' GO Now let us go over some of the fantastic solutions which we have received. Response from Rainmaker SELECT CASE PATINDEX('%[^0 ]%', Col1 + ' ‘') WHEN 0 THEN '' ELSE SUBSTRING(Col1, PATINDEX('%[^0 ]%', Col1 + ' '), LEN(Col1)) END FROM Table1 Response from Harsh Solution 1 SELECT SUBSTRING(Col1, PATINDEX('%[^0 ]%', Col1 + 'a'), LEN(Col1)) FROM Table1 Response from Harsh Solution 2 SELECT RIGHT(Col1, LEN(Col1)+1 -PATINDEX('%[^0 ]%', Col1 + 'a' )) FROM Table1 Response from lucazav SELECT T.Col1 , label = CAST( CAST(REPLACE(T.Col1, ' ', '') AS FLOAT) AS VARCHAR(10)) FROM Table1 AS T Response from iamAkashSingh SELECT REPLACE(LTRIM(REPLACE(col1,'0',' ')),' ','0') FROM table1 Here is the resultset of above scripts. It will remove any leading zero or space and will display the number accordingly. If you believe there is a better solution, please leave a comment. I am just glad to see so many various responses and all of them teach us something new. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Validating If Date is Last Day of the Year, Month or Day

  - by Pinal Dave

  Here is one more question I recently received in an email- “Pinal, is there any ready made function which will display if the given date is the last day or the year, month or day? For example, if a date is the last day of the Year and last day of the month, I want to display Last Day of the Year and if a date is the last date of the month and last day of the week, I want to display the last day of the week. “ Well, very interesting question and there is no such function available for the same. However, here is the function I have written earlier for my personal use where I almost accomplish same task. -- Example of Year DECLARE @Day DATETIME SET @Day = '2014-12-31' SELECT CASE WHEN CAST(@Day AS DATE) = CAST(DATEADD(ms,-3,DATEADD(yy,0,DATEADD(yy,DATEDIFF(yy,0,@Day)+1,0))) AS DATE) THEN 'LastDayofYear' WHEN CAST(@Day AS DATE) = CAST(DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,@Day)+1,0)) AS DATE) THEN 'LastDayofMonth' WHEN CAST(@Day AS DATE) = CAST(DATEADD(s,-1,DATEADD(wk, DATEDIFF(wk,0,@Day),0)) AS DATE) THEN 'LastDayofWeek' ELSE 'Day' END GO -- Example of Month DECLARE @Day DATETIME SET @Day = '2014-06-30' SELECT CASE WHEN CAST(@Day AS DATE) = CAST(DATEADD(ms,-3,DATEADD(yy,0,DATEADD(yy,DATEDIFF(yy,0,@Day)+1,0))) AS DATE) THEN 'LastDayofYear' WHEN CAST(@Day AS DATE) = CAST(DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,@Day)+1,0)) AS DATE) THEN 'LastDayofMonth' WHEN CAST(@Day AS DATE) = CAST(DATEADD(s,-1,DATEADD(wk, DATEDIFF(wk,0,@Day),0)) AS DATE) THEN 'LastDayofWeek' ELSE 'Day' END GO -- Example of Month DECLARE @Day DATETIME SET @Day = '2014-05-04' SELECT CASE WHEN CAST(@Day AS DATE) = CAST(DATEADD(ms,-3,DATEADD(yy,0,DATEADD(yy,DATEDIFF(yy,0,@Day)+1,0))) AS DATE) THEN 'LastDayofYear' WHEN CAST(@Day AS DATE) = CAST(DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,@Day)+1,0)) AS DATE) THEN 'LastDayofMonth' WHEN CAST(@Day AS DATE) = CAST(DATEADD(s,-1,DATEADD(wk, DATEDIFF(wk,0,@Day),0)) AS DATE) THEN 'LastDayofWeek' ELSE 'Day' END GO Let me know if you know any other smarter trick and we can post it here with due credit. Reference: Pinal Dave (http://blog.SQLAuthority.com)Filed under: PostADay, SQL, SQL Authority, SQL DateTime, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• SQL SERVER – Two Puzzles – Answer and Win USD 25 Gift Card

  - by pinaldave

  Today I have two simple T-SQL Puzzle. You can answer them and win USD 25 Gift card. The gift card will be sent in email to winner. You will get choice of Gift Card brand based on your preference and country location. Puzzle 1: What will be the outcome and why? DECLARE @x REAL; SET @x = 9E-40 SELECT @x; The outcome here is obvious as I have used negative number in assignment. What is the reason behind the same? Puzzle 2: Why will be the outcome different from Puzzle 1: DECLARE @y REAL; SET @y = 9E+40 SELECT @y; The outcome of this puzzle very different from puzzle 1  as I have used positive number. There is number six (6) in the resultset why? Msg 232, Level 16, State 2, Line 2 Arithmetic overflow error for type real, value = 90000000000000006000000000000000000000000.000000. How to participate To win the Gift Card USD 25 you will have to answer both of the question on my Facebook page. If you are on twitter – you can increase the chance of winning by tweeting your participation. This contest is open for any one from any country. The winner will be selected Randomly. Winner will be announced on July 7, 2011. Related Post: SQLAuthority News – Monthly list of Puzzles and Solutions on SQLAuthority.com Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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• SQL SERVER – UNION ALL and ORDER BY – How to Order Table Separately While Using UNION ALL

  - by pinaldave

  I often see developers trying following syntax while using ORDER BY. SELECT Columns FROM TABLE1 ORDER BY Columns UNION ALL SELECT Columns FROM TABLE2 ORDER BY Columns However the above query will return following error. Msg 156, Level 15, State 1, Line 5 Incorrect syntax near the keyword ‘ORDER’. It is not possible to use two different ORDER BY in the UNION statement. UNION returns single resultsetand as per the Logical Query Processing Phases. However, if your requirement is such that you want your top and bottom query of the UNION resultset independently sorted but in the same resultset you can add an additional static column and order by that column. Let us re-create the same scenario. First create two tables and populated with sample data. USE tempdb GO -- Create table CREATE TABLE t1 (ID INT, Col1 VARCHAR(100)); CREATE TABLE t2 (ID INT, Col1 VARCHAR(100)); GO -- Sample Data Build INSERT INTO t1 (ID, Col1) SELECT 1, 'Col1-t1' UNION ALL SELECT 2, 'Col2-t1' UNION ALL SELECT 3, 'Col3-t1'; INSERT INTO t2 (ID, Col1) SELECT 3, 'Col1-t2' UNION ALL SELECT 2, 'Col2-t2' UNION ALL SELECT 1, 'Col3-t2'; GO If we SELECT the data from both the table using UNION ALL . -- SELECT without ORDER BY SELECT ID, Col1 FROM t1 UNION ALL SELECT ID, Col1 FROM t2 GO We will get the data in following order. However, our requirement is to get data in following order. If we need data ordered by Column1 we can ORDER the resultset ordered by Column1. -- SELECT with ORDER BY SELECT ID, Col1 FROM t1 UNION ALL SELECT ID, Col1 FROM t2 ORDER BY ID GO Now to get the data in independently sorted in UNION ALL let us add additional column OrderKey and use ORDER BY  on that column. I think the description does not do proper justice let us see the example here. -- SELECT with ORDER BY - with ORDER KEY SELECT ID, Col1, 'id1' OrderKey FROM t1 UNION ALL SELECT ID, Col1, 'id2' OrderKey FROM t2 ORDER BY OrderKey, ID GO The above query will give the desired result. Now do not forget to clean up the database by running the following script. -- Clean up DROP TABLE t1; DROP TABLE t2; GO Here is the complete script used in this example. USE tempdb GO -- Create table CREATE TABLE t1 (ID INT, Col1 VARCHAR(100)); CREATE TABLE t2 (ID INT, Col1 VARCHAR(100)); GO -- Sample Data Build INSERT INTO t1 (ID, Col1) SELECT 1, 'Col1-t1' UNION ALL SELECT 2, 'Col2-t1' UNION ALL SELECT 3, 'Col3-t1'; INSERT INTO t2 (ID, Col1) SELECT 3, 'Col1-t2' UNION ALL SELECT 2, 'Col2-t2' UNION ALL SELECT 1, 'Col3-t2'; GO -- SELECT without ORDER BY SELECT ID, Col1 FROM t1 UNION ALL SELECT ID, Col1 FROM t2 GO -- SELECT with ORDER BY SELECT ID, Col1 FROM t1 UNION ALL SELECT ID, Col1 FROM t2 ORDER BY ID GO -- SELECT with ORDER BY - with ORDER KEY SELECT ID, Col1, 'id1' OrderKey FROM t1 UNION ALL SELECT ID, Col1, 'id2' OrderKey FROM t2 ORDER BY OrderKey, ID GO -- Clean up DROP TABLE t1; DROP TABLE t2; GO I am sure there are many more ways to achieve this, what method would you use if you have to face the similar situation? Reference: Pinal Dave (http://blog.sqlauthority.com)   Filed under: Best Practices, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Where to Perform Authentication in REST API Server?

  - by David V

  I am working on a set of REST APIs that needs to be secured so that only authenticated calls will be performed. There will be multiple web apps to service these APIs. Is there a best-practice approach as to where the authentication should occur? I have thought of two possible places. Have each web app perform the authentication by using a shared authentication service. This seems to be in line with tools like Spring Security, which is configured at the web app level. Protect each web app with a "gateway" for security. In this approach, the web app never receives unauthenticated calls. This seems to be the approach of Apache HTTP Server Authentication. With this approach, would you use Apache or nginx to protect it, or something else in between Apache/nginx and your web app? For additional reference, the authentication is similar to services like AWS that have a non-secret identifier combined with a shared secret key. I am also considering using HMAC. Also, we are writing the web services in Java using Spring. Update: To clarify, each request needs to be authenticated with the identifier and secret key. This is similar to how AWS REST requests work.

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• SQL SERVER – Function to Round Up Time to Nearest Minutes Interval

  - by pinaldave

  Though I have written more than 2300 blog posts, I always find things which I have not covered earlier in this blog post. Recently I was asked if I have written a function which rounds up or down the time based on the minute interval passed to it. Well, not earlier but it is here today. Here is a very simple example of how one can do the same. ALTER FUNCTION [dbo].[RoundTime] (@Time DATETIME, @RoundToMin INT) RETURNS DATETIME AS BEGIN RETURN ROUND(CAST(CAST(CONVERT(VARCHAR,@Time,121) AS DATETIME) AS FLOAT) * (1440/@RoundToMin),0)/(1440/@RoundToMin) END GO Above function needs two values. 1) The time which needs to be rounded up or down. 2) Time in minutes (the value passed here should be between 0 and 60 – if the value is incorrect the results will be incorrect.) Above function can be enhanced by adding functionalities like a) Validation of the parameters passed b) Accepting values like Quarter Hour, Half Hour etc. Here are few sample examples. SELECT dbo.roundtime1('17:29',30) SELECT dbo.roundtime1(GETDATE(),5) SELECT dbo.roundtime1('2012-11-02 07:27:07.000',15) When you run above code, it will return following results. Well, do you have any other way to achieve the same result? If yes, do share it here and I will be glad to share it on blog with due credit. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL DateTime, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Select Columns from Stored Procedure Resultset

  - by Pinal Dave

  It is fun to go back to basics often. Here is the one classic question: “How to select columns from Stored Procedure Resultset?” Though Stored Procedure has been introduced many years ago, the question about retrieving columns from Stored Procedure is still very popular with beginners. Let us see the solution in quick steps. First we will create a sample stored procedure. CREATE PROCEDURE SampleSP AS SELECT 1 AS Col1, 2 AS Col2 UNION SELECT 11, 22 GO Now we will create a table where we will temporarily store the result set of stored procedures. We will be using INSERT INTO and EXEC command to retrieve the values and insert into temporary table. CREATE TABLE #TempTable (Col1 INT, Col2 INT) GO INSERT INTO #TempTable EXEC SampleSP GO Next we will retrieve our data from stored procedure. SELECT * FROM #TempTable GO Finally we will clean up all the objects which we have created. DROP TABLE #TempTable DROP PROCEDURE SampleSP GO Let me know if you want me to share such back to basic tips. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Stored Procedure, SQL Tips and Tricks, T SQL

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• SQL SERVER – Technical Reference Guides for Designing Mission-Critical Solutions – A Must Read

  - by pinaldave

  Yesterday I was reading architecture reference material helping my friend who was looking for material in this respect. While working together we were searching twitter, facebook and search engines to find relevant material.While searching online we end up on very interactive reference point. Once I send the same to him, he replied he may not need anything more after referencing this material. The best part of this article was it gives access to various aspect of the technology of the image map. Here is the abstract of the original article from the site: The Technical Reference Guides for Designing Mission-Critical Solutions provide planning and architecture guidance for various mission-critical workloads deployed by users. These guides reflect the knowledge gained by Microsoft while working with customers on mission-critical deployments. Each guide provides not only the key technical concepts and information helpful for design, but also “lessons learned,” best practices, and references to customer case studies. Once you click on any of the desired topic, you will see further detailed image map of the selected topic. Personally once I ended up on this site, I was there for more than 2 hours clicking through various links. Click on image to see larger image Read more here: Technical Reference Guides for Designing Mission-Critical Solutions Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL White Papers, T SQL, Technology

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• SQL SERVER – Fix: Error: 8117: Operand data type bit is invalid for sum operator

  - by pinaldave

  Here is the very interesting error I received from a reader. He has very interesting question. He attempted to use BIT filed in the SUM aggregation function and he got following error. He went ahead with various different datatype (i.e. INT, TINYINT etc) and he was able to do the SUM but with BIT he faced the problem. Error Received: Msg 8117, Level 16, State 1, Line 1 Operand data type bit is invalid for sum operator. Reproduction of the error: Set up the environment USE tempdb GO -- Preparing Sample Data CREATE TABLE TestTable (ID INT, Flag BIT) GO INSERT INTO TestTable (ID, Flag) SELECT 1, 0 UNION ALL SELECT 2, 1 UNION ALL SELECT 3, 0 UNION ALL SELECT 4, 1 GO SELECT * FROM TestTable GO Following script will work fine: -- This will work fine SELECT SUM(ID) FROM TestTable GO However following generate error: -- This will generate error SELECT SUM(Flag) FROM TestTable GO The workaround is to convert or cast the BIT to INT: -- Workaround of error SELECT SUM(CONVERT(INT, Flag)) FROM TestTable GO Clean up the setup -- Clean up DROP TABLE TestTable GO Workaround: As mentioned in above script the workaround is to covert the bit datatype to another friendly data types like INT, TINYINT etc. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Grouping by Multiple Columns to Single Column as A String

  - by pinaldave

  One of the most common questions I receive in email is how to group multiple column data in comma separate values in a single row grouping by another column. I have previously blogged about it in following two blog posts. However, both aren’t addressing the following exact problem. Comma Separated Values (CSV) from Table Column Comma Separated Values (CSV) from Table Column – Part 2 The question comes in many different formats but in following image I am demonstrating the same question in simple words. This is the most popular question on my Facebook page as well. (Example) Here is the sample script to build the sample dataset. CREATE TABLE TestTable (ID INT, Col VARCHAR(4)) GO INSERT INTO TestTable (ID, Col) SELECT 1, 'A' UNION ALL SELECT 1, 'B' UNION ALL SELECT 1, 'C' UNION ALL SELECT 2, 'A' UNION ALL SELECT 2, 'B' UNION ALL SELECT 2, 'C' UNION ALL SELECT 2, 'D' UNION ALL SELECT 2, 'E' GO SELECT * FROM TestTable GO Here is the solution which will build an answer to the above question. -- Get CSV values SELECT t.ID, STUFF( (SELECT ',' + s.Col FROM TestTable s WHERE s.ID = t.ID FOR XML PATH('')),1,1,'') AS CSV FROM TestTable AS t GROUP BY t.ID GO I hope this is an easy solution. I am going to point to this blog post in the future for all the similar questions. Final Clean Up Act -- Clean up DROP TABLE TestTable GO Here is the question back to you - Is there any better way to write above script? Please leave a comment and I will write a separate blog post with due credit. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: SQL XML

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• Server outputs the sourcecode of PHP page

  - by Akhilesh B Chandran

  I have a Shared Hosting package with HostGator. In it, I'm hosting around 4 websites. They are just some simple sites that doesn't likely to attract more visitors. But a few days ago, when I accessed one of my sites(via a browser), it outputted the PHP code of index.php, instead of outputting it as HTML. I think, at that time, the server was a bit busy or something. I heard that, Facebook also have got a similar condition where the home page's code was made available. So, how do I take preventive measures for this ? I always use phpBB forum's style of coding. That is, each sub pages, common functions, etc. are separated into subfolders. And in PHP, I would just include_once() or require_once() it. Also, these subfolders have a .htaccess file in which I have set the deny permission to the files inside it from outside. Also, in the main page(index), I would define a constant. And the first line of the subpages(which is situated in separate folders) is to check whether this constant is set. If not, calls die(). I am looking forward for solutions to this problem of outputting raw code when the page is accessed. Thanks in advance :)

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• Ubuntu 10.04 LTS Server - fresh install - failed apt-get update

  - by user87227

  Good day and greetings to all, I just did a fresh installation of Ubuntu 10.04 LTS server without any issues. However, the apt-get update or aptitude update is giving the following errors: a. bzip2:(stdin) is not bzip2 file.ign for all lines plus the following errors : etched 3,582B in 0s (74.1kB/s) Reading package lists... W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: //security.ubuntu.com lucid-security Release: The following signatures were invalid: NODATA 1 NODATA 2 W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: //in.archive.ubuntu.com lucid Release: The following signatures were invalid: NODATA 1 NODATA 2 W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: in.archive.ubuntu.com lucid-updates Release: The following signatures were invalid: NODATA 1 NODATA 2 W: Failed to fetch security.ubuntu.com/ubuntu/dists/lucid-security/Release W: Failed to fetch in.archive.ubuntu.com/ubuntu/dists/lucid/Release W: Failed to fetch in.archive.ubuntu.com/ubuntu/dists/lucid-updates/Release W: Some index files failed to download, they have been ignored, or old ones used instead. Please guide in resolving this error. TIA Regards Venu

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• SQL SERVER – Using RAND() in User Defined Functions (UDF)

  - by pinaldave

  Here is the question I received in email. “Pinal, I am writing a function where we need to generate random password. While writing T-SQL I faced following issue. Everytime I tried to use RAND() function in my User Defined Function I am getting following error: Msg 443, Level 16, State 1, Procedure RandFn, Line 7 Invalid use of a side-effecting operator ‘rand’ within a function. Here is the simplified T-SQL code of the function which I am using: CREATE FUNCTION RandFn() RETURNS INT AS BEGIN DECLARE @rndValue INT SET @rndValue = RAND() RETURN @rndValue END GO I must use UDF so is there any workaround to use RAND function in UDF.” Here is the workaround how RAND() can be used in UDF. The scope of the blog post is not to discuss the advantages or disadvantages of the function or random function here but just to show how RAND() function can be used in UDF. RAND() function is directly not allowed to use in the UDF so we have to find alternate way to use the same function. This can be achieved by creating a VIEW which is using RAND() function and use the same VIEW in the UDF. Here is the step by step instructions. Create a VIEW using RAND function. CREATE VIEW rndView AS SELECT RAND() rndResult GO Create a UDF using the same VIEW. CREATE FUNCTION RandFn() RETURNS DECIMAL(18,18) AS BEGIN DECLARE @rndValue DECIMAL(18,18) SELECT @rndValue = rndResult FROM rndView RETURN @rndValue END GO Now execute the UDF and it will just work fine and return random result. SELECT dbo.RandFn() GO In T-SQL world, I have noticed that there are more than one solution to every problem. Is there any better solution to this question? Please post that question as a comment and I will include it with due credit. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: technology

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• Worker roles in Windows Azure to host a multiplayer server

  - by MrWiggels

  I've been doing research on where to host a simple multi-player backend for a simple game I'm developing. So as a first choice I downloaded the Windows Azure SDK, which provides a nice and simple emulator environment where you can test out your application before uploading. I also download the Azure Social Game Toolkit (Visit), and followed as far as my understanding can take me. So, down to the main question. Is there anybody with experience developing Azure applications. I'm developing a Action RPG game, in a similar vein to Diablo III. I was thinking of putting up Matchmaking, Friends Lists, etc. Is there another way to connect to Azure services via something like UDP or TCP for sending packets or does everything have to go through HTTP requests? Is it even possible to use HTTP request/response for something like this? All game commands will be simple. Because the game server and the clients will be kept in-sync and will have deterministic actions, I'm just going to send actions like "Use Primary Skill" and "Use Secondary Skill". Any hints, ideas, light bulbs or a smack-in-the-face presentation will be much appreciated.

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• Two Upcoming Server Virtualization Webcasts

  - by Chris Kawalek

  We have a couple of interesting server virtualization webcasts coming up that you might be interested in. Have a look:  Webcast 1: October 23rd, 9 am PST Virtualized Infrastructure Simplified with Oracle VM and NetApp Storage and Data Management Solutions Point-and-Click Interface Deploys Virtualized Data Infrastructure in Minutes  Provisioning and deploying a virtual data infrastructure can be costly, time-consuming, and prone to error. Oracle VM and NetApp joint solutions, however, give you a single point-and-click interface to deploy your virtualized data infrastructure seamlessly in minutes. Join us in this live webcast to learn more from product experts and view a product demo. Register (for free!) here.  Webcast 2: November 7th, 9 am PST Report Shows Oracle VM Up to 10x Faster than VMware vSphere 5 in Time to Deployment Time is your IT department’s greatest commodity. So when a new report reveals that your IT staff can deploy Oracle Real Application Clusters (Oracle RAC) up to 10 times faster than a traditional install performed with VMware vSphere 5, it’s newsworthy. Join us in this live webcast to learn how you can realize your time savings. Register (for free!) here. 

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• Ubuntu Server 11.10 boot, white terminal with garbled black text

  - by SpeedCrazy

  I just installed Ubuntu server 11.10 and the install went fine. This system is running on an Intel Pentium II board with onboard graphics. However when I try to boot into Ubuntu I get a white terminal with garbled black text. I have tried various grub 'fixes' as googling the issue seemed to suggest it was a res or grub related issue. I cannot ssh in so the issue does affect Linux as well. I have had no luck with anything thus far and am at my wits end. This was my first Ubuntu excursion as my friend told me it was better for servers than CentOS because it was easier... Not so much.... Does anyone have any ideas as to what the issue could be? When answering bear in mind I am an Ubuntu noob and Linux novice. As of 1/26/12 I have tried to add the console=ttyl line to the /etc/default/grub and run update-grub. This results in the line in the boot parameters that normally reads: linux /vmlunz-3.0.0-12-generic-pae root=/dev/mapper/dev-root rovt.handoff=7 now reads: linux /vmlunz-3.0.0-12-generic-pae root=/dev/mapper/dev-root ro console=ttyl vt.handoff=7 This does not work. Is there anyway to have console=ttyl inserted on a line by itself? I am at my wits ends, Thanks for all your help, Speed

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• How to choose a server side language / framework

  - by pllee

  I am trying to come up with a list / ranking system on determining which server language to choose for a particular website. Assume that familiarity with a certain language is not important and the implementation can be done in any language. Here are some things that might be important but I am not sure how to rank them : Maintainability. Libraries. For example, Memcached and NoSql support right out the box would be really nice addition to a particular framework. 3rd party SDK's. For example, if I need Paypal on my site they openly provide SDK's for all senarios in Java, PHP and .Net. If I choose Django I would have to rely on 3rd party libraries that are don't support everything and are not officially maintained. Would that be dealbreaker for Django? Performance This one is tricky to put on a generic list because it can be a deal breaker but for many websites performance will not be an issue that the language/framework is responsible for. Cost (hosting, open source). edit - Any reason for the votes to close? I didn't see any duplicates mentioned and the question should not drum up a flame war.

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• Client-server application design issue

  - by user2547823

  I have a collection of clients on server's side. And there are some objects that need to work with that collection - adding and removing clients, sending message to them, updating connection settings and so on. They should perform these actions simultaneously, so mutex or another synchronization primitive is required. I want to share one instance of collection between these objects, but all of them require access to private fields of collection. I hope that code sample makes it more clear[C++]: class Collection { std::vector< Client* > clients; Mutex mLock; ... } class ClientNotifier { void sendMessage() { mLock.lock(); // loop over clients and send message to each of them } } class ConnectionSettingsUpdater { void changeSettings( const std::string& name ) { mLock.lock(); // if client with this name is inside collection, change its settings } } As you can see, all these classes require direct access to Collection's private fields. Can you give me an advice about how to implement such behaviour correctly, i.e. keeping Collection's interface simple without it knowing about its users?

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