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  • Merge\Combine two datatables

    - by madlan
    I'm trying to merge\combine two datatables. I've looked at various examples and answers but they seem to create duplicate rows or require indexes (merge on datatable etc) I can't do this via SQL as one source is from a linked Oracle server accessed via MSSQL and the other from a different MSSQL Server that does not have linked access. The data is currently very simple: Name, Email, Phone DataTable1: "John Clark", "", "01522 55231" "Alex King", "[email protected]", "01522 55266" "Marcus Jones", "[email protected]", "01522 55461" DataTable2: "John Clark", "john[email protected]", "01522 55231" "Alex King", "[email protected]", "" "Marcus Jones", "[email protected]", "01522 55461" "Warren bean", "[email protected]", "01522 522311" Giving a datatable with the following: "John Clark", "john[email protected]", "01522 55231" "Alex King", "[email protected]", "01522 55266" "Marcus Jones", "[email protected]", "01522 55461" "Warren bean", "[email protected]", "01522 522311" Name is the field to match records on, with the first datatable taking priority.

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  • To ref or not to ref

    - by nmarun
    So the question is what is the point of passing a reference type along with the ref keyword? I have an Employee class as below: 1: public class Employee 2: { 3: public string FirstName { get; set; } 4: public string LastName { get; set; } 5:  6: public override string ToString() 7: { 8: return string.Format("{0}-{1}", FirstName, LastName); 9: } 10: } In my calling class, I say: 1: class Program 2: { 3: static void Main() 4: { 5: Employee employee = new Employee 6: { 7: FirstName = "John", 8: LastName = "Doe" 9: }; 10: Console.WriteLine(employee); 11: CallSomeMethod(employee); 12: Console.WriteLine(employee); 13: } 14:  15: private static void CallSomeMethod(Employee employee) 16: { 17: employee.FirstName = "Smith"; 18: employee.LastName = "Doe"; 19: } 20: }   After having a look at the code, you’ll probably say, Well, an instance of a class gets passed as a reference, so any changes to the instance inside the CallSomeMethod, actually modifies the original object. Hence the output will be ‘John-Doe’ on the first call and ‘Smith-Doe’ on the second. And you’re right: So the question is what’s the use of passing this Employee parameter as a ref? 1: class Program 2: { 3: static void Main() 4: { 5: Employee employee = new Employee 6: { 7: FirstName = "John", 8: LastName = "Doe" 9: }; 10: Console.WriteLine(employee); 11: CallSomeMethod(ref employee); 12: Console.WriteLine(employee); 13: } 14:  15: private static void CallSomeMethod(ref Employee employee) 16: { 17: employee.FirstName = "Smith"; 18: employee.LastName = "Doe"; 19: } 20: } The output is still the same: Ok, so is there really a need to pass a reference type using the ref keyword? I’ll remove the ‘ref’ keyword and make one more change to the CallSomeMethod method. 1: class Program 2: { 3: static void Main() 4: { 5: Employee employee = new Employee 6: { 7: FirstName = "John", 8: LastName = "Doe" 9: }; 10: Console.WriteLine(employee); 11: CallSomeMethod(employee); 12: Console.WriteLine(employee); 13: } 14:  15: private static void CallSomeMethod(Employee employee) 16: { 17: employee = new Employee 18: { 19: FirstName = "Smith", 20: LastName = "John" 21: }; 22: } 23: } In line 17 you’ll see I’ve ‘new’d up the incoming Employee parameter and then set its properties to new values. The output tells me that the original instance of the Employee class does not change. Huh? But an instance of a class gets passed by reference, so why did the values not change on the original instance or how do I keep the two instances in-sync all the times? Aah, now here’s the answer. In order to keep the objects in sync, you pass them using the ‘ref’ keyword. 1: class Program 2: { 3: static void Main() 4: { 5: Employee employee = new Employee 6: { 7: FirstName = "John", 8: LastName = "Doe" 9: }; 10: Console.WriteLine(employee); 11: CallSomeMethod(ref employee); 12: Console.WriteLine(employee); 13: } 14:  15: private static void CallSomeMethod(ref Employee employee) 16: { 17: employee = new Employee 18: { 19: FirstName = "Smith", 20: LastName = "John" 21: }; 22: } 23: } Viola! Now, to prove it beyond doubt, I said, let me try with another reference type: string. 1: class Program 2: { 3: static void Main() 4: { 5: string name = "abc"; 6: Console.WriteLine(name); 7: CallSomeMethod(ref name); 8: Console.WriteLine(name); 9: } 10:  11: private static void CallSomeMethod(ref string name) 12: { 13: name = "def"; 14: } 15: } The output was as expected, first ‘abc’ and then ‘def’ - proves the 'ref' keyword works here as well. Now, what if I remove the ‘ref’ keyword? The output should still be the same as the above right, since string is a reference type? 1: class Program 2: { 3: static void Main() 4: { 5: string name = "abc"; 6: Console.WriteLine(name); 7: CallSomeMethod(name); 8: Console.WriteLine(name); 9: } 10:  11: private static void CallSomeMethod(string name) 12: { 13: name = "def"; 14: } 15: } Wrong, the output shows ‘abc’ printed twice. Wait a minute… now how could this be? This is because string is an immutable type. This means that any time you modify an instance of string, new memory address is allocated to the instance. The effect is similar to ‘new’ing up the Employee instance inside the CallSomeMethod in the absence of the ‘ref’ keyword. Verdict: ref key came to the rescue and saved the planet… again!

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  • SQL group and order

    - by John Lambert
    I have multiple users with multiple entries recording times they arrive at destinations Somehow, with my select query I would like to only show the most recent entries for each unique user name. Here is the code that doesn't work: SELECT * FROM $dbTable GROUP BY xNAME ORDER BY xDATETIME DESC This does the name grouping fine, but as far as showing ONLY their most recent entry, is just shows the first entry it sees in the SQL table. I guess my question is, is this possible? Here is my data sample: john 7:00 chris 7:30 greg 8:00 john 8:15 greg 8:30 chris 9:00 and my desired result should only be john 8:15 chris 9:00 greg 8:30

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  • C# - Determine if class initializaion causes infinite recursion?

    - by John M
    I am working on porting a VB6 application to C# (Winforms 3.5) and while doing so I'm trying to break up the functionality into various classes (ie database class, data validation class, string manipulation class). Right now when I attempt to run the program in Debug mode the program pauses and then crashes with a StackOverFlowException. VS 2008 suggests a infinite recursion cause. I have been trying to trace what might be causing this recursion and right now my only hypothesis is that class initializations (which I do in the header(?) of each class). My thought is this: mainForm initializes classA classA initializes classB classB initializes classA .... Does this make sense or should I be looking elsewhere? UPDATE1 (a code sample): mainForm namespace john { public partial class frmLogin : Form { stringCustom sc = new sc(); stringCustom namespace john { class stringCustom { retrieveValues rv = new retrieveValues(); retrieveValues namespace john { class retrieveValues { stringCustom sc = new stringCustom();

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  • Oracle Transportation Management Annual Customer Conference

    - by [email protected]
    The 2010 Oracle Transportation Management (OTM) Conference will be held June 13-16 in Philadelphia, Pennsylvania. The conference brings together all things OTM: users, prospective users, development personnel, product strategy, implementation experts, and software and services partners.  With over 200 attendees, this conference is the premiere location and time to learn about OTM, build relationships with peers, and get answers to all your OTM questions.    This year's conference will be held at the: Sheraton Society Hill, One Dock St., Philadelphia, PA. 19106Companies speaking at this year's event include:AT&T Land O Lakes BlueScope Steel Baillie Lumber Kraft Sears Roseburg Forest Products Toyota Beckman CoulterLevi StraussNiagara BottlingSmurfit StonePQ CorporationOffice Depot               To register click here http://www.otmconference.com/ConfAgenda.aspx.  1

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  • struct assignment operator on arrays

    - by Django fan
    Suppose I defined a structure like this: struct person { char name [10]; int age; }; and declared two person variables: person Bob; person John; where Bob.name = "Bob", Bob.age = 30 and John.name = "John",John.age = 25. and I called Bob = John; struct person would do a Memberwise assignment and assign Johns's member values to Bob's. But arrays can't assign to arrays, so how does the assignment of the "name" array work?

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  • How do I average the difference between specific values in TSQL?

    - by jvenema
    Hey folks, sorry this is a bit of a longer question... I have a table with the following columns: [ChatID] [User] [LogID] [CreatedOn] [Text] What I need to find is the average response time for a given user id, to another specific user id. So, if my data looks like: [1] [john] [20] [1/1/11 3:00:00] [Hello] [1] [john] [21] [1/1/11 3:00:23] [Anyone there?] [1] [susan] [22] [1/1/11 3:00:43] [Hello!] [1] [susan] [23] [1/1/11 3:00:53] [What's up?] [1] [john] [24] [1/1/11 3:01:02] [Not much] [1] [susan] [25] [1/1/11 3:01:08] [Cool] ...then I need to see that Susan has an average response time of (20 + 6) / 2 = 13 seconds to John, and John has an average of (9 / 1) = 9 seconds to Susan. I'm not even sure this can be done in set-based logic, but if anyone has any ideas, they'd be much appreciated!

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  • Must I loop to search results for a specific value?

    - by tag
    I have a table in the database: name Opinion Tim Tim has an opinion John other random text Dan Dan's random text Al Al says something else I call this data and get it back in getRecords.lastResult To access John's opinion, I could use: getRecords.lastResult[1].opinion But that's only because I know that John is the second record (record 1), but this may change. So the right way is to search through the results to first find the record index for John, then access his opinion. My guess is I need some sort of a loop? Is there an easier way to search for John directly without a loop?

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  • Installing CUDA on Ubuntu 12.04 with nvidia driver 295.59

    - by johnmcd
    I have been trying to get cuda to run on a nvidia gt 650m based laptop. I am running Ubuntu 12.04 with the nvidia 295.59 driver. Also, my laptop uses Optimus so I have install the driver via bumblebee. Bumblebee is not working correctly yet -- however I believe it is possible to install CUDA independently. To install CUDA I have followed the instructions detailed here: How can I get nVidia CUDA or OpenCL working on a laptop with nVidia discrete card/Intel Integrated Graphics? However I am still running into problem building the sdk. I made the changes specified at the above link in common.mk, but I got the following (snippet) from the build process: make[2]: Entering directory `/home/john/NVIDIA_GPU_Computing_SDK/C/src/fluidsGL' /usr/bin/ld: warning: libnvidia-tls.so.302.17, needed by /usr/lib/nvidia-current/libGL.so, not found (try using -rpath or -rpath-link) /usr/bin/ld: warning: libnvidia-glcore.so.302.17, needed by /usr/lib/nvidia-current/libGL.so, not found (try using -rpath or -rpath-link) /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv018tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv012glcore' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv017glcore' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv012tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv015tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv019tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv000glcore' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv017tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv013tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv013glcore' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv018glcore' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv022tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv007tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv009tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv020tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv014glcore' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv015glcore' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv016tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv001glcore' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv006tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv021tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv011tls' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv020glcore' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv019glcore' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv002glcore' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv021glcore' /usr/lib/nvidia-current/libGL.so: undefined reference to `_nv014tls' collect2: ld returned 1 exit status make[2]: *** [../../bin/linux/release/fluidsGL] Error 1 make[2]: Leaving directory `/home/john/NVIDIA_GPU_Computing_SDK/C/src/fluidsGL' make[1]: *** [src/fluidsGL/Makefile.ph_build] Error 2 make[1]: Leaving directory `/home/john/NVIDIA_GPU_Computing_SDK/C' make: *** [all] Error 2 The libraries that ld warns about are on my system and are installed on the system: $ locate libnvidia-tls.so.302.17 libnvidia-glcore.so.302.17 /usr/lib/nvidia-current/libnvidia-glcore.so.302.17 /usr/lib/nvidia-current/libnvidia-tls.so.302.17 /usr/lib/nvidia-current/tls/libnvidia-tls.so.302.17 /usr/lib32/nvidia-current/libnvidia-glcore.so.302.17 /usr/lib32/nvidia-current/libnvidia-tls.so.302.17 /usr/lib32/nvidia-current/tls/libnvidia-tls.so.302.17 however /usr/lib/nvidia-current and /usr/lib32/nvidia-current are not being picked up by ldconfig. I have tried adding them by adding a file to /etc/ld.so.conf.d/ which gets past this error, however now I am getting the following error: make[2]: Entering directory `/home/john/NVIDIA_GPU_Computing_SDK/C/src/deviceQueryDrv' cc1plus: warning: command line option ‘-Wimplicit’ is valid for C/ObjC but not for C++ [enabled by default] obj/x86_64/release/deviceQueryDrv.cpp.o: In function `main': deviceQueryDrv.cpp:(.text.startup+0x5f): undefined reference to `cuInit' deviceQueryDrv.cpp:(.text.startup+0x99): undefined reference to `cuDeviceGetCount' deviceQueryDrv.cpp:(.text.startup+0x10b): undefined reference to `cuDeviceComputeCapability' deviceQueryDrv.cpp:(.text.startup+0x127): undefined reference to `cuDeviceGetName' deviceQueryDrv.cpp:(.text.startup+0x16a): undefined reference to `cuDriverGetVersion' deviceQueryDrv.cpp:(.text.startup+0x1f0): undefined reference to `cuDeviceTotalMem_v2' deviceQueryDrv.cpp:(.text.startup+0x262): undefined reference to `cuDeviceGetAttribute' deviceQueryDrv.cpp:(.text.startup+0x457): undefined reference to `cuDeviceGetAttribute' deviceQueryDrv.cpp:(.text.startup+0x4bc): undefined reference to `cuDeviceGetAttribute' deviceQueryDrv.cpp:(.text.startup+0x502): undefined reference to `cuDeviceGetAttribute' deviceQueryDrv.cpp:(.text.startup+0x533): undefined reference to `cuDeviceGetAttribute' obj/x86_64/release/deviceQueryDrv.cpp.o:deviceQueryDrv.cpp:(.text.startup+0x55e): more undefined references to `cuDeviceGetAttribute' follow collect2: ld returned 1 exit status make[2]: *** [../../bin/linux/release/deviceQueryDrv] Error 1 make[2]: Leaving directory `/home/john/NVIDIA_GPU_Computing_SDK/C/src/deviceQueryDrv' make[1]: *** [src/deviceQueryDrv/Makefile.ph_build] Error 2 make[1]: Leaving directory `/home/john/NVIDIA_GPU_Computing_SDK/C' make: *** [all] Error 2 I would appreciate any help that anyone can provide me with. If I can provide any further information please let me know. Thanks.

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  • Checking data of all same class elements

    - by Tiffani
    I need the code to check the data-name value of all instances of .account-select. Right now it just checks the first .account-select element and not any subsequent ones. The function right now is on click of an element such as John Smith, it checks the data-name of the .account-select lis. If the data-names are the same, it does not create a new li with the John Smith data. If no data-names are equal to John Smith, then it adds an li with John Smith. This is the JS-Fiddle I made for it so you can see what I am referring to: http://jsfiddle.net/rsxavior/vDCNy/22/ Any help would be greatly appreciated. This is the Jquery Code I am using right now. $('.account').click(function () { var acc = $(this).data("name"); var sel = $('.account-select').data("name"); if (acc === sel) { } else { $('.account-hidden-li').append('<li class="account-select" data-name="'+ $(this).data("name") +'">' + $(this).data("name") + '<a class="close bcn-close" data-dismiss="alert" href="#">&times;</a></li>'); } }); And the HTML: <ul> <li><a class="account" data-name="All" href="#">All</a></li> <li><a class="account" data-name="John Smith" href="#">John Smith</a></li> </ul> <ul class="account-hidden-li"> <ul>

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  • Pattern/Matcher in Java?

    - by user1007059
    I have a certain text in Java, and I want to use pattern and matcher to extract something from it. This is my program: public String getItemsByType(String text, String start, String end) { String patternHolder; StringBuffer itemLines = new StringBuffer(); patternHolder = start + ".*" + end; Pattern pattern = Pattern.compile(patternHolder); Matcher matcher = pattern.matcher(text); while (matcher.find()) { itemLines.append(text.substring(matcher.start(), matcher.end()) + "\n"); } return itemLines.toString(); } This code works fully WHEN the searched text is on the same line, for instance: String text = "My name is John and I am 18 years Old"; getItemsByType(text, "My", "John"); immediately grabs the text "My name is John" out of the text. However, when my text looks like this: String text = "My name\nis John\nand I'm\n18 years\nold"; getItemsByType(text, "My", "John"); It doesn't grab anything, since "My" and "John" are on different lines. How do I solve this?

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  • Parsing back to 'messy' API strcuture

    - by Eric Fail
    I'm fetching data from an online database (REDcap) via API and the data gets delivered in as comma separated string like this, RAW.API <- structure("id,event_arm,name,dob,pushed_text,pushed_calc,complete\n\"01\",\"event_1_arm_1\",\"John\",\"1979-05-01\",\"\",\"\",2\n\"01\",\"event_2_arm_1\",\"John\",\"2012-09-02\",\"abc\",\"123\",1\n\"01\",\"event_3_arm_1\",\"John\",\"2012-09-10\",\"\",\"\",2\n\"02\",\"event_1_arm_1\",\"Mary\",\"1951-09-10\",\"def\",\"456\",2\n\"02\",\"event_2_arm_1\",\"Mary\",\"1978-09-12\",\"\",\"\",2\n", "`Content-Type`" = structure(c("text/html", "utf-8"), .Names = c("", "charset"))) I have this script that nicely parses it into a data frame, (df <- read.table(file = textConnection(RAW.API), header = TRUE, sep = ",", na.strings = "", stringsAsFactors = FALSE)) id event_arm name dob pushed_text pushed_calc complete 1 1 event_1_arm_1 John 1979-05-01 <NA> NA 2 2 1 event_2_arm_1 John 2012-09-02 abc 123 1 3 1 event_3_arm_1 John 2012-09-10 <NA> NA 2 4 2 event_1_arm_1 Mary 1951-09-10 def 456 2 5 2 event_2_arm_1 Mary 1978-09-12 <NA> NA 2 I then do some calculations and write them to pushed_text and pushed_calc whereafter I need to format the data back to the messy comma separated structure it came in. I imagine something like this, API.back <- `some magic command`(df, ...) identical(RAW.API, API.back) [1] TRUE Some command that can format my data from the data frame I made, df, back to the structure that the raw API-object came in, RAW.API. Any help would be very appreciated.

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  • July, the 31 Days of SQL Server DMO’s – Day 2 (sys.dm_exec_sessions)

    - by Tamarick Hill
      This sys.dm_exec_sessions DMV is another Server-Scoped DMV which returns information for each authenticated session that is running on your SQL Server box. Lets take a look at some of the information that this DMV returns. SELECT * FROM sys.dm_exec_sessions This DMV is very similar to the DMV we reviewed yesterday, sys.dm_exec_requests, and returns some of the same information such as reads, writes, and status for a given session_id (SPID). But this DMV returns additional information such as the Host name of the machine that owns the SPID, the program that is being used to connect to SQL Server, and the Client interface name. In addition to this information, this DMV also provides useful information on session level settings that may be on or off such as quoted identifier, arithabort, ansi padding, ansi nulls, etc. This DMV will also provide information about what specific isolation level the session is executing under and if the default deadlock priority for your SPID has been changed from the default. Lastly, this DMV provides you with an Original Login Name, which comes in handy whenever you have some type of context switching taking place due to an ‘EXECUTE AS’ statement being used and you need to identify the original login that started a session. For more information on this DMV, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms176013.aspx

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  • July, the 31 Days of SQL Server DMO’s – Day 22 (sys.dm_db_index_physical_stats)

    - by Tamarick Hill
    The sys.dm_db_index_physical_stats Dynamic Management Function is used to return information about the fragmentation levels, page counts, depth, number of levels, record counts, etc. about the indexes on your database instance. One row is returned for each level in a given index, which we will discuss more later. The function takes a total of 5 input parameters which are (1) database_id, (2) object_id, (3) index_id, (4) partition_number, and (5) the mode of the scan level that you would like to run. Let’s use this function with our AdventureWorks2012 database to better illustrate the information it provides. SELECT * FROM sys.dm_db_index_physical_stats(db_id('AdventureWorks2012'), NULL, NULL, NULL, NULL) As you can see from the result set, there is a lot of beneficial information returned from this DMF. The first couple of columns in the result set (database_id, object_id, index_id, partition_number, index_type_desc, alloc_unit_type_desc) are either self-explanatory or have been explained in our previous blog sessions so I will not go into detail about these at this time. The next column in the result set is the index_depth which represents how deep the index goes. For example, If we have a large index that contains 1 root page, 3 intermediate levels, and 1 leaf level, our index depth would be 5. The next column is the index_level which refers to what level (of the depth) a particular row is referring to. Next is probably one of the most beneficial columns in this result set, which is the avg_fragmentation_in_percent. This column shows you how fragmented a particular level of an index may be. Many people use this column within their index maintenance jobs to dynamically determine whether they should do REORG’s or full REBUILD’s of a given index. The fragment count represents the number of fragments in a leaf level while the avg_fragment_size_in_pages represents the number of pages in a fragment. The page_count column tells you how many pages are in a particular index level. From my result set above, you see the the remaining columns all have NULL values. This is because I did not specify a ‘mode’ in my query and as a result it used the ‘LIMITED’ mode by default. The LIMITED mode is meant to be lightweight so it does collect information for every column in the result set. I will re-run my query again using the ‘DETAILED’ mode and you will see we now have results for these rows. SELECT * FROM sys.dm_db_index_physical_stats(db_id('AdventureWorks2012'), NULL, NULL, NULL, ‘DETAILED’)   From the remaining columns, you see we get even more detailed information such as how many records are in a particular index level (record_count). We have a column for ghost_record_count which represents the number of records that have been marked for deletion, but have not physically been removed by the background ghost cleanup process. We later see information on the MIN, MAX, and AVG record size in bytes. The forwarded_record_count column refers to records that have been updated and now no longer fit within the row on the page anymore and thus have to be moved. A forwarded record is left in the original location with a pointer to the new location. The last column in the result set is the compressed_page_count column which tells you how many pages in your index have been compressed. This is a very powerful DMF that returns good information about the current indexes in your system. However, based on the mode you select, it could be a very resource intensive function so be careful with how you use it. For more information on this Dynamic Management Function, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms188917.aspx Follow me on Twitter @PrimeTimeDBA

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  • July, the 31 Days of SQL Server DMO’s – Day 23 (sys.dm_db_index_usage_stats)

    - by Tamarick Hill
    The sys.dm_db_index_usage_stats Dynamic Management View is used to return usage information about the various indexes on your SQL Server instance. Let’s have a look at this DMV against our AdventureWorks2012 database so we can examine the information returned. SELECT * FROM sys.dm_db_index_usage_stats WHERE database_id = db_id('AdventureWorks2012') The first three columns in the result set represent the database_id, object_id, and index_id of a given row. You can join these columns back to other system tables to extract the actual database, object, and index names. The next four columns are probably the most beneficial columns within this DMV. First, the user_seeks column represents the number of times that a user query caused a seek operation against a particular index. The user_scans column represents how many times a user query caused a scan operation on a particular index. The user_lookups column represents how many times an index was used to perform a lookup operation. The user_updates column refers to how many times an index had to be updated due to a write operation that effected a particular index. The last_user_seek, last_user_scan, last_user_lookup, and last_user_update columns provide you with DATETIME information about when the last user scan, seek, lookup, or update operation was performed. The remaining columns in the result set are the same as the ones we previously discussed, except instead of the various operations being generated from user requests, they are generated from system background requests. This is an extremely useful DMV and one of my favorites when it comes to Index Maintenance. As we all know, indexes are extremely beneficial with improving the performance of your read operations. But indexes do have a downside as well. Indexes slow down the performance of your write operations, and they also require additional resources for storage. For this reason, in my opinion, it is important to regularly analyze the indexes on your system to make sure the indexes you have are being used efficiently. My AdventureWorks2012 database is only used for demonstrating or testing things, so I dont have a lot of meaningful information here, but for a Production system, if you see an index that is never getting any seeks, scans, or lookups, but is constantly getting a ton of updates, it more than likely would be a good candidate for you to consider removing. You would not be getting much benefit from the index, but yet it is incurring a cost on your system due to it constantly having to be updated for your write operations, not to mention the additional storage it is consuming. You should regularly analyze your indexes to ensure you keep your database systems as efficient and lean as possible. One thing to note is that these DMV statistics are reset every time SQL Server is restarted. Therefore it would not be a wise idea to make decisions about removing indexes after a Server Reboot or a cluster roll. If you restart your SQL Server instances frequently, for example if you schedule weekly/monthly cluster rolls, then you may not capture indexes that are being used for weekly/monthly reports that run for business users. And if you remove them, you may have some upset people at your desk on Monday morning. If you would like to begin analyzing your indexes to possibly remove the ones that your system is not using, I would recommend building a process to load this DMV information into a table on scheduled basis, depending on how frequently you perform an operation that would reset these statistics, then you can analyze the data over a period of time to get a more accurate view of what indexes are really being used and which ones or not. For more information about this DMV, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms188755.aspx Follow me on Twitter @PrimeTimeDBA

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  • July, the 31 Days of SQL Server DMO’s – Day 1 (sys.dm_exec_requests)

    - by Tamarick Hill
    The first DMO that I would like to introduce you to is one of the most common and basic DMV’s out there. I use the term DMV because this DMO is actually a view as opposed to a function. This DMV is server-scoped and it returns information about all requests that are currently executing on your SQL Server instance. To illustrate what this DMV returns, lets take a look at the results. As you can see, this DMV returns a wealth of information about requests occurring on your server. You are able to see the SPID, the start time of a request, current status, and the command the SPID is executing. In addition to this you see columns for sql_handle and plan_handle. These columns (when combined with other DMO’s we will discuss later) can return the actual sql text that is being executed on your server as well as the actual execution plan that is cached and being used. This DMV also returns information about various wait types that may be occurring for your spid. The percent_complete column displays a percentage to completion for certain database actions such as DBCC CheckDB, Database Restores, Rollback’s, etc. In addition to these, you are also able to see the amount of reads, writes, and cpu that the SPID has consumed. You will find this DMV to be one of the primary DMV’s that you use when looking for information about what is occurring on your server.

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  • July, the 31 Days of SQL Server DMO’s - Intro

    - by Tamarick Hill
    DMO’s burst onto the SQL Server scene in 2005 and when they did they unlocked a wealth of information. I’ve became a major fan of DMO’s as they tend to simplify my troubleshooting as well as provide me with valuable information about what is going on within the SQL Server engine. I would recommend that those of you who are not familiar with DMO’s, take the time to really learn more about them. For those of you who may not be familiar with DMO’s, for the month of July, I will be writing about one DMO per day. Don’t get me wrong, I’m no DMO expert or anything like that, but I’ve worked with them enough to feel that I can give you some good information about DMO’s to help you get started with using them. During these blog sessions, I will not be providing you with any complicated queries to solve all of your SQL Server problems that you may or may not have. I will be simply introducing you to various DMO’s and illustrating what type of information they provide. After you learn more about these individually, then you will be able to join whatever DMO’s you need to pull back the information you are seeking. I hope that you all benefit in some form or fashion from my next 31 DMO postings!!! Enjoy!

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  • July, the 31 Days of SQL Server DMO’s – Day 20 (sys.dm_tran_locks)

    - by Tamarick Hill
    The sys.dm_tran_locks DMV is used to return active lock resources on your server. Locking is a mechanism used by SQL Server to protect the integrity of data when you have multiple users that may potentially access the same data at the same time. Let’s run a query against this DMV so we can analyze the results. SELECT * FROM sys.dm_tran_locks As we can see, its a lot of lock information returned from this DMV. I will not go into detail about each of the columns returned, but I will touch on the ones that I feel are the most important. The first column in the output is the resource_type column which tells you the type of lock a particular row represents. It could be a PAGE lock, RID, OBJECT, DATABASE, or several other lock types. The resource_database_id represents the id of the database for a particular lock resource. The resource_lock_partition column represents the ID of a lock partition. When you have a table that is partitioned, locks can be escalated to the partition level before going to a table level lock. The request_mode column gives us information about the type of lock that is being requested. From the screenshots above we see RangeS-S locks which represent a share range lock and IS locks which represent Intent Shared locks. The request_status column displays whether the lock has been granted or whether the lock is waiting to be acquired. The request_session_id  shows the session_id that is requesting the lock. This DMV is the best place to go when you need to identify the exact locks that are being held or pending for individual requests. You might need this information when you are troubleshooting severe blocking or deadlocking problems on your server. For more information on this DMV, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms190345.aspx Follow me on Twitter @PrimeTimeDBA

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  • July, the 31 Days of SQL Server DMO’s – Day 19 (sys.dm_exec_query_stats)

    - by Tamarick Hill
    The sys.dm_exec_query_stats DMV is one of the most useful DMV’s out there when it comes to performance tuning. If you have been keeping up with this blog series this month, you know that I started out on Day 1 reviewing many of the DMV’s within the ‘exec’ namespace. I’m not sure how I missed this one considering how valuable it is, but hey, they say it’s better late than never right?? On Day 7 and Day 8 we reviewed the sys.dm_exec_procedure_stats and sys.dm_exec_trigger_stats respectively. This sys.dm_exec_query_stats DMV is very similar to these two. As a matter of fact, this DMV will return all of the information you saw in the other two DMV’s, but in addition to that, you can see stats for all queries that have cached execution plans on your server. You can even see stats for statements that are ran Ad-Hoc as long as they are still cached in the buffer pool. To better illustrate this DMV, let have a quick look at it: SELECT * FROM sys.dm_exec_query_stats As you can see, there is a lot of information returned from this DMV. I wont go into detail about each and every one of these columns, but I will touch on a few of them briefly. The first column is the ‘sql_handle’, which if you remember from Day 4 of our blog series, I explained how you can use this column to extract the actual SQL text that was executed. The next columns statement_start_offset and statement_end_offset provide you a way of extracting the exact SQL statement that was executed as part of a batch. The plan_handle column is used to extract the Execution plan that was used, which we talked about during Day 5 of this blog series. Later in the result set, you have columns to identify how many times a particular statement was executed, how much CPU time it used, how many reads/writes it performed, the duration, how many rows were returned, etc. These columns provide you with a solid avenue to begin your performance optimization. The last column I will touch on is the query_plan_hash column. A lot of times when you have Dynamic SQL running on your server, you have similar statements with different parameter values being passed in. Many times these types of statements will get similar execution plans and then a Binary hash value can be generated based on these similar plans. This query plan hash can be used to find the cost of all queries that have similar execution plans and then you can tune based on that plan to improve the performance of all of the individual queries. This is a very powerful way of identifying and tuning Ad-hoc statements that run on your server. As I stated earlier, this sys.dm_exec_query_stats DMV is a very powerful and recommended DMV for performance tuning. You are able to quickly identify statements that are running on your server and analyze their impact on system resources. Using this DMV to track down the biggest performance killers on your server will allow you to make the biggest gains once you focus your tuning efforts on those top offenders. For more information about this DMV, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms189741.aspx Follow me on Twitter @PrimeTimeDBA

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  • July, the 31 Days of SQL Server DMO’s – Day 27 (sys.dm_db_file_space_usage)

    - by Tamarick Hill
    The sys.dm_db_file_space usage DMV returns information about database file space usage.  This DMV was enhanced for the 2012 version to include 3 additional columns. Let’s query this DMV against our AdventureWorks2012 database and view the results. SELECT * FROM sys.dm_db_file_space_usage The column returned from this DMV are really self-explanatory, but I will give you a description, paraphrased from books online, below. The first three columns returned from this DMV represent the Database, File, and Filegroup for the current database context that executed the DMV query. The next column is the total_page_count which represents the total number of pages in the file. The allocated_extent_page_count represents the total number of pages in all extents that have been allocated. The unallocated_extent_page_count represents the number of pages in the unallocated extents within the file. The version_store_reserved_page_count column represents the number of pages that are allocated to the version store. The user_object_reserved_page_count represents the number of pages allocated for user objects. The internal_object_reserved_page_count represents the number of pages allocated for internal objects.  Lastly is the mixed_extent_page_count which represents the total number of pages that are part of mixed extents. This is a great DMV for retrieving usage space information from your database files. For more information about this DMV, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms174412.aspx Follow me on Twitter @PrimeTimeDBA

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  • July, the 31 Days of SQL Server DMO’s – Day 18 (sys.dm_io_virtual_file_stats)

    - by Tamarick Hill
    The sys.dm_io_virtual_file_stats Dynamic Management Function is used to return IO statistic information about each of your database files on your server. As input parameters, this function takes a database_id and a file_id. If you want to return IO statistic information for all files, you can simply pass in NULL values for both of these. Let’s have a look at this function  and examine its results: SELECT db_name(database_id) DatabaseName, * FROM sys.dm_io_virtual_file_stats(NULL, NULL) The first column in the result set is the DatabaseName which is just a column I created using the db_name() system function and the database_id column from this function. Next we have a file_id which represent the ID for the file, whether it be a data file or transaction log file. The ‘sample_ms’ column represents the total time in milliseconds that the instance has been up and running. Next we have the ‘num_of_reads’, ‘num_of_bytes_read’, and later ‘num_of_writes’, and ‘num_of_bytes_written’. These columns represent the number of reads or writes and number of bytes read or written against a particular file. These columns are beneficial when determining how often a particular file is being accessed. The ‘io_stall_read_ms’ and io_stall_write_ms’ columns each represent the the total time in milliseconds that users have had to wait for reads or writes against a file respectively. The ‘io_stall’ column is the sum of both read and write io stalls. The ‘size_on_disk_bytes’ column represents the size of the respective file on your disk subsystem. Lastly the ‘file_handle’ column is simply the Windows File handle. This Dynamic Management Function is useful when you are needing to analyze your database files for the purposes of segregating high IO databases. This DMF gives you a good view of which of your database files are being accessed the most and which ones may be generating the largest IO stalls. These could be your best candidates for moving into separate IO channels. For more information about this DMF, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms190326.aspx Follow me on Twitter @PrimeTimeDBA

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  • July, the 31 Days of SQL Server DMO’s – Day 21 (sys.dm_db_partition_stats)

    - by Tamarick Hill
    The sys.dm_db_partition_stats DMV returns page count and row count information for each table or index within your database. Lets have a quick look at this DMV so we can review some of the results. **NOTE: I am going to create an ‘ObjectName’ column in our result set so that we can more easily identify tables. SELECT object_name(object_id) ObjectName, * FROM sys.dm_db_partition_stats As stated above, the first column in our result set is an Object name based on the object_id column of this result set. The partition_id column refers to the partition_id of the index in question. Each index will have at least 1 unique partition_id and will have more depending on if the object has been partitioned. The index_id column relates back to the sys.indexes table and uniquely identifies an index on a given object. A value of 0 (zero) in this column would indicate the object is a HEAP and a value of 1 (one) would signify the Clustered Index. Next is the partition_number which would signify the number of the partition for a particular object_id. Since none of my tables in my result set have been partitioned, they all display 1 for the partition_number. Next we have the in_row_data_page_count which tells us the number of data pages used to store in-row data for a given index. The in_row_used_page_count is the number of pages used to store and manage the in-row data. If we look at the first row in the result set, we will see we have 700 for this column and 680 for the previous. This means that just to manage the data (not store it) is requiring 20 pages. The next column in_row_reserved_page_count is how many pages have been reserved, regardless if they are being used or not. The next 2 columns are used for storing LOB (Large Object) data which could be text, image, varchar(max), or varbinary(max) columns. The next two columns, row_overflow, represent pages used for data that exceed the 8,060 byte row size limit for the in-row data pages. The next columns used_page_count and reserved_page_count represent the sum of the in_row, lob, and row_overflow columns discussed earlier. Lastly is a row_count column which displays the number of rows that are in a particular index. This DMV is a very powerful resource for identifying page and row count information. By knowing the page counts for indexes within your database, you are able to easily calculate the size of indexes. For more information on this DMV, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms187737.aspx Follow me on Twitter @PrimeTimeDBA

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  • July, the 31 Days of SQL Server DMO’s – Day 24 (sys.dm_db_index_operational_stats)

    - by Tamarick Hill
    The sys.dm_db_index_operational_stats Dynamic Management Function returns information about the IO, locking, and access methods for the indexes that you currently have on your SQL Server Instance. This function takes four input parameters which are (1) database_id, (2) object_id, (3) index_id, and (4) partition_number. Let’s have a look at the results from this function against our AdventureWorks2012 database. This function returns a ton of columns, so not only will I not attempt to describe each of the columns, I wont even attempt to display all of them here. My query below will give you a subset of the columns returned from this function. SELECT database_id, object_id, index_id, partition_number, leaf_insert_count, leaf_delete_count, leaf_update_count, leaf_ghost_count, nonleaf_insert_count, nonleaf_delete_count, nonleaf_update_count, range_scan_count, forwarded_fetch_count, row_lock_count, row_lock_wait_count, page_lock_count, page_lock_wait_count, Index_lock_promotion_attempt_count, index_lock_promotion_count, page_compression_attempt_count, page_compression_success_count FROM sys.dm_db_index_operational_stats(db_id('AdventureWorks2012'), NULL, NULL, NULL) The first four columns in the result set represent the values that we passed in as our input parameters. If you use NULL’s as I did, then you will see results for every index on your system. I specified a database_id so my result set only shows those records pertaining to my AdventureWorks2012 database. The next columns in the result set provide you with information on how may inserts, deletes, or updates that have taken place on your leaf and nonleaf index levels. The nonleaf levels would refer to the intermediate and root index levels. In the middle of these you see a leaf_ghost_count column, which represents the number of records that have been logically deleted and marked as “ghosted”  and are waiting on the background ghost cleanup process to physically remove them. The range_scan_count column represents the number of range or table scans that have been performed against an index. The forwarded_fetch_count column represents the number of rows that were returned from a forwarding row pointer. The row_lock_count and row_lock_wait_count represent the number of row locks that have been requested for an index and the number of times SQL has had to wait on a row lock respectively. The page_lock_count and page_lock_wait_count represent the number of page locks that have been requested for an index and the number of times SQL has had to wait on a page lock respectively. The index_lock_promotion_attempt_count represents the number of times the database engine has attempted to promote a lock to the index level. The index_lock_promotion_count column displays how many times that index lock promotion was successful. Lastly the page_compression_attempt_count and page_compression_success_count represents how many times a page was attempted to be compressed and how many times the attempt was successful. As you can see there is a ton of information returned from this DMV. The DMV we reviewed on yesterday (sys.dm_db_index_usage_stats) provided you with good information on when and how indexes have been used, but this DMF takes an even deeper dive into these statistics. If you are interested in performing a very detailed analysis on the operational stats of your indexes, this is not only a good place to start, but more than likely the best place. For more information on this Dynamic Management Function, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms174281.aspx Follow me on Twitter @PrimeTimeDBA

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