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  • Rename INDEX Column

    - by Lee
    Hey All I have a database with around 40 tables and need to rename every index column. IE USER a table has a bunch of fields like user_id | user_username | user_password | etc... I want to rename the ID columns just to id ie id | user_username | user_password | etc... But I keep getting mysql errors on the alter table command ie. ALTER TABLE database RENAME COLUMN user_id to id; Plus many different variations. Whats the best way to do this ? Hope you can advise

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  • multiline column in data grid view. using c#

    - by syedsaleemss
    Im using c# .net windows form application. i have a datagrid view. It has two columns.I need to make all the cells on the second column as to have multiple line. i.e a multiline column. I will edit something in a cell and press enter key. the cursor should reach the next line in the same cell. It should not go to the next cell. What should i do?

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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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  • living column in instruments

    - by dubbeat
    In the context of allocations what exactly does the living column mean? Does it mean the number of times an object was created or does it mean how many instances of an object there is? I ask because I'm testing going in and out of a view. When I enter the view I create a class "myClass". When I exit the view I nil "myClass" and release it. If I go in and out of the view 6 times for example the living column in instruments for "myClass" says 6. Is this normal or is it not being released properly?

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  • SSIS - user variable used in derived column transform is not available - in some cases

    - by soo
    Unfortunately I don't have a repro for my issue, but I thought I would try to describe it in case it sounds familiar to someone... I am using SSIS 2005, SP2. My package has a package-scope user variable - let's call it user_var first step in the control flow is an Execute SQL task which runs a stored procedure. All that SP does is insert a record in a SQL table (with an identity column) and then go back and get the max ID value. The Execute SQL task saves this output into user_var the control flow then has a Data Flow Task - it goes and gets some source data, has a derived column which sets a column called run_id to user_var - and saves the data to a SQL destination In most cases (this template is used for many packages, running every day) this all works great. All of the destination records created get set with a correct run_id. However, in some cases, there is a set of the destination data that does not get run_id equal to user_var, but instead gets a value of 0 (0 is the default value for user_var). I have 2 instances where this has happened, but I can't make it happen. In both cases, it was just less that 10,000 records that have run_id = 0. Since SSIS writes data out in 10,000 record blocks, this really makes me think that, for the first set of data written out, user_var was not yet set. Then, after that first block, for the rest of the data, run_id is set to a correct value. But control passed on to my data flow from the Execute SQL task - it would have seemed reasonable to me that it wouldn't go on until the SP has completed and user_var is set. Maybe it just runs the SP, but doesn't wait for it to complete? In both cases where this has happened there seemed to be a few packages hitting the table to get a new user_var at about the same time. And in both cases lots of data was written (40 million rows, 60 million rows) - my thinking is that that means the writes were happening for a while. Sorry to be both long-winded AND vague. A winning combination! Does this sound familiar to anyone? Thanks.

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  • SQL: How to use a column that was just added

    - by sbenderli
    I am trying to add 2 columns and then I would like to set some values to them but I get a compile-error saying the column does not exist. I am using the following script: IF NOT EXISTS (select column_name from INFORMATION_SCHEMA.columns where table_name = 'SYSTM_FRM' and column_name = 'SF_Ip_TXT') ALTER TABLE SYSTM_FRM add SF_Ip_TXT NVARCHAR(20) IF NOT EXISTS (select column_name from INFORMATION_SCHEMA.columns where table_name = 'SYSTM_FRM' and column_name = 'SF_Port_NUM') ALTER TABLE SYSTM_FRM add SF_Port_NUM int Update dbo.SYSTM_FRM SET dbo.SYSTM_FRM.SF_Ip_TXT = dbo.FRM.FRM_Ip_TXT, dbo.SYSTM_FRM.SF_Port_NUM = dbo.FRM.FRM_Port_NUM FROM dbo.FRM INNER JOIN dbo.SYSTM_FRM ON dbo.FRM.FRM_RCRD_NUM = dbo.SYSTM_FRM.SF_FrameRecord_NUM Is there any way to use a column that I am adding in the same script?

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  • Search for string within text column in MySQL

    - by user94154
    I have mysql table that has a column that stores xml as a string. I need to find all tuples where the xml column contains a given string of 6 characters. Nothing else matters--all I need to know is if this 6 character string is there or not. So it probably doesn't matter that the text is formatted as xml. Question: how can I search within mysql? ie SELECT * FROM items WHERE items.xml [contains the text '123456'] Is there a way I can use the LIKE operator to do this? Thanks

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  • adding count( ) column on each row

    - by Arsenal
    I'm not sure if this is even a good question or not. I have a complex query with lot's of unions that searches multiple tables for a certain keyword (user input). All tables in which there is searched are related to the table book. There is paging on the resultset using LIMIT, so there's always a maximum of 10 results that get withdrawn. I want an extra column in the resultset displaying the total amount of results found however. I do not want to do this using a seperate query. Is it possible to add a count() column to the resultset that counts every result found? the output would look like this: ID Title Author Count(...) 1 book_1 auth_1 23 2 book_2 auth_2 23 4 book_4 auth_.. 23 ... Thanks!

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  • 2 Column Layout - Main Link Display

    - by Allyson Aguilar
    I have a basic HTML page with a 2 column layout. I created a menu page on the sidebar column and when a link is chosen from the menu I want to display it in the main section of the index.html page. I tried doing this with iframes but its basically creating a duplicate of the index page. Help! I guess I can't post a picture because I'm new to this but I basically have an index page and then a farm with a duplicate of my index page.

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  • MySQL column names and aliases

    - by user329820
    hi, I have read that after select we use column-names but I have found a statement that was like this: SELECT 'A' FROM T WHERE A = NULL; would you lease help me? thanks (A is a column- name here?) my DBMS is MySQL EDITED : the exact question is this that: Will the above statement produce a row (select all that apply)? Notice that ANSI_NULLS is OFF. I want to know that the above statement will work? because some of you said that we should write IS NULL instead of =null

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  • SQL Check Constraint cannot reference other column

    - by user1777711
    I trying to add this sql check in ALTER TABLE School add Role check_role CHECK (check_role IN ('Teaching Assistant', 'Lecturer', 'Professor')); I get the error below ERROR at line 3: ORA-02438: Column check constraint cannot reference other columns SQL> desc School; Name Null? Type ----------------------------------------- -------- ---------------------------- STAFFNUM NOT NULL VARCHAR2(12) NAME NOT NULL VARCHAR2(50) ADDRESS NOT NULL VARCHAR2(300) DOB DATE I am trying add a column call Role, with the check constraint check_role I am using Oracle SQL. Thanks for all help!

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  • Changing populated DataTable column data types

    - by TonE
    Hi, I have a System.Data.DataTable which is populated by reading a CSV file which sets the datatype of each column to string. I want to append the contents of the DataTable to an existing database table - currently this is done using SqlBulkCopy with the DataTable as the source. However, the column data types of the DataTable need to be changed to match the schema of the target database table, handling null values. I am not very familiar with ADO.NET so have been search for a clean way of doing this? Thanks.

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  • Outer select column value in joined subquery?

    - by Michael DePetrillo
    Is it possible to use a column value from an outer select within a joined subquery? SELECT table1.id, table2.cnt FROM table1 LEFT JOIN (SELECT COUNT(*) as `cnt` FROM table2 where table2.lt > table1.lt and table2.rt < table1.rt) as table2 ON 1; This results in "Unknown column 'table1.lt' in 'where clause'". Here is the db dump. CREATE TABLE IF NOT EXISTS `table1` ( `id` int(1) NOT NULL, `lt` int(1) NOT NULL, `rt` int(4) NOT NULL) ENGINE=MyISAM DEFAULT CHARSET=latin1; CREATE TABLE IF NOT EXISTS `table2` ( `id` int(1) NOT NULL, `lt` int(1) NOT NULL, `rt` int(4) NOT NULL) ENGINE=MyISAM DEFAULT CHARSET=latin1; INSERT INTO `table1` (`id`, `lt`, `rt`) VALUES (1, 1, 4); INSERT INTO `table2` (`id`, `lt`, `rt`) VALUES (2, 2, 3);

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  • July, the 31 Days of SQL Server DMO’s – Day 28 (sys.dm_db_stats_properties)

    - by Tamarick Hill
    The sys.dm_db_stats_properties Dynamic Management Function returns information about the statistics that are currently on your database objects. This function takes two parameters, an object_id and a stats_id. Let’s have a look at the result set from this function against the AdventureWorks2012.Sales.SalesOrderHeader table. To obtain the object_id and stats_id I will use a CROSS APPLY with the sys.stats system table. SELECT sp.* FROM sys.stats s CROSS APPLY sys.dm_db_stats_properties(s.object_id, s.Stats_id) sp WHERE sp.object_id = object_id('Sales.SalesOrderHeader') The first two columns returned by this function are the object_id and the stats_id columns. The next column, ‘last_updated’, gives you the date and the time that a particular statistic was last updated. The next column, ‘rows’, gives you the total number of rows in the table as of the last statistic update date. The ‘rows_sampled’ column gives you the number of rows that were sampled to create the statistic. The ‘steps’ column represents the number of specific value ranges from the statistic histogram. The ‘unfiltered_rows’ column represents the number of rows before any filters are applied. If a particular statistic is not filtered, the ‘unfiltered_rows’ column will always equal the ‘rows’ column. Lastly we have the ‘modification_counter’ column which represents the number of modification to the leading column in a given statistic since the last time the statistic was updated. Probably the most important column from this Dynamic Management Function is the ‘last_updated’ column. You want to always ensure that you have accurate and updated statistics on your database objects. Accurate statistics are vital for the query optimizer to generate efficient and reliable query execution plans. Without accurate and updated statistics, the performance of your SQL Server would likely suffer. For more information about this Dynamic Management Function, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/jj553546.aspx Folllow me on Twitter @PrimeTimeDBA

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  • SQL SERVER – Validating Unique Columnname Across Whole Database

    - by pinaldave
    I sometimes come across very strange requirements and often I do not receive a proper explanation of the same. Here is the one of those examples. Asker: “Our business requirement is when we add new column we want it unique across current database.” Pinal: “Why do you have such requirement?” Asker: “Do you know the solution?” Pinal: “Sure I can come up with the answer but it will help me to come up with an optimal answer if I know the business need.” Asker: “Thanks – what will be the answer in that case.” Pinal: “Honestly I am just curious about the reason why you need your column name to be unique across database.” (Silence) Pinal: “Alright – here is the answer – I guess you do not want to tell me reason.” Option 1: Check if Column Exists in Current Database IF EXISTS (  SELECT * FROM sys.columns WHERE Name = N'NameofColumn') BEGIN SELECT 'Column Exists' -- add other logic END ELSE BEGIN SELECT 'Column Does NOT Exists' -- add other logic END Option 2: Check if Column Exists in Current Database in Specific Table IF EXISTS (  SELECT * FROM sys.columns WHERE Name = N'NameofColumn' AND OBJECT_ID = OBJECT_ID(N'tableName')) BEGIN SELECT 'Column Exists' -- add other logic END ELSE BEGIN SELECT 'Column Does NOT Exists' -- add other logic END I guess user did not want to share the reason why he had a unique requirement of having column name unique across databases. Here is my question back to you – have you faced a similar situation ever where you needed unique column name across a database. If not, can you guess what could be the reason for this kind of requirement?  Additional Reference: SQL SERVER – Query to Find Column From All Tables of Database Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL System Table, SQL Tips and Tricks, T SQL, Technology

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  • finding numbers of days between two date to make a dynamic columns

    - by Chandradyani
    Dear all, I have a select query that currently produces the following results: DoctorName Team 1 2 3 4 5 6 7 ... 31 Visited dr. As   A                             x    x ...      2 times dr. Sc   A                          x          ...      1 times dr. Gh   B                                  x ...      1 times dr. Nd   C                                     ... x    1 times Using the following query: DECLARE @startDate = '1/1/2010', @enddate = '1/31/2010' SELECT d.doctorname, t.teamname, MAX(CASE WHEN ca.visitdate = 1 THEN 'x' ELSE NULL END) AS 1, MAX(CASE WHEN ca.visitdate = 2 THEN 'x' ELSE NULL END) AS 2, MAX(CASE WHEN ca.visitdate = 3 THEN 'x' ELSE NULL END) AS 3, ... MAX(CASE WHEN ca.visitdate = 31 THEN 'x' ELSE NULL END) AS 31, COUNT(*) AS visited FROM CACTIVITY ca JOIN DOCTOR d ON d.id = ca.doctorid JOIN TEAM t ON t.id = ca.teamid WHERE ca.visitdate BETWEEN @startdate AND @enddate GROUP BY d.doctorname, t.teamname the problem is I want to make the column of date are dynamic for example if ca.visitdate BETWEEN '2/1/2012' AND '2/29/2012' so the result will be : DoctorName Team 1 2 3 4 5 6 7 ... 29 Visited dr. As   A                             x    x ...      2 times dr. Sc   A                          x          ...      1 times dr. Gh   B                                  x ...      1 times dr. Nd   C                                     ... x    1 times Can somebody help me how to get numbers of days between two date and help me revised the query so it can looping MAX(CASE WHEN ca.visitdate = 1 THEN 'x' ELSE NULL END) AS 1 as many as numbers of days? Please please

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  • How to insert and call by row and column into sqlite3 python, great tutorial problem.

    - by user291071
    Lets say i have a simple array of x rows and y columns with corresponding values, What is the best method to do 3 things? How to insert, update a value at a specific row column? How to select a value for each row and column, import sqlite3 con = sqlite3.connect('simple.db') c = con.cursor() c.execute('''create table simple (links text)''') con.commit() dic = {'x1':{'y1':1.0,'y2':0.0},'x2':{'y1':0.0,'y2':2.0,'y3':1.5},'x3':{'y2':2.0,'y3':1.5}} ucols = {} ## my current thoughts are collect all row values and all column values from dic and populate table row and columns accordingly how to call by row and column i havn't figured out yet ##populate rows in first column for row in dic: print row c.execute("""insert into simple ('links') values ('%s')"""%row) con.commit() ##unique columns for row in dic: print row for col in dic[row]: print col ucols[col]=dic[row][col] ##populate columns for col in ucols: print col c.execute("alter table simple add column '%s' 'float'" % col) con.commit() #functions needed ##insert values into sql by row x and column y?how to do this e.g. x1 and y2 should put in 0.0 ##I tried as follows didn't work for row in dic: for col in dic[row]: val =dic[row][col] c.execute("""update simple SET '%s' = '%f' WHERE 'links'='%s'"""%(col,val,row)) con.commit() ##update value at a specific row x and column y? ## select a value at a specific row x and column y?

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  • Beware Sneaky Reads with Unique Indexes

    - by Paul White NZ
    A few days ago, Sandra Mueller (twitter | blog) asked a question using twitter’s #sqlhelp hash tag: “Might SQL Server retrieve (out-of-row) LOB data from a table, even if the column isn’t referenced in the query?” Leaving aside trivial cases (like selecting a computed column that does reference the LOB data), one might be tempted to say that no, SQL Server does not read data you haven’t asked for.  In general, that’s quite correct; however there are cases where SQL Server might sneakily retrieve a LOB column… Example Table Here’s a T-SQL script to create that table and populate it with 1,000 rows: CREATE TABLE dbo.LOBtest ( pk INTEGER IDENTITY NOT NULL, some_value INTEGER NULL, lob_data VARCHAR(MAX) NULL, another_column CHAR(5) NULL, CONSTRAINT [PK dbo.LOBtest pk] PRIMARY KEY CLUSTERED (pk ASC) ); GO DECLARE @Data VARCHAR(MAX); SET @Data = REPLICATE(CONVERT(VARCHAR(MAX), 'x'), 65540);   WITH Numbers (n) AS ( SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 0)) FROM master.sys.columns C1, master.sys.columns C2 ) INSERT LOBtest WITH (TABLOCKX) ( some_value, lob_data ) SELECT TOP (1000) N.n, @Data FROM Numbers N WHERE N.n <= 1000; Test 1: A Simple Update Let’s run a query to subtract one from every value in the some_value column: UPDATE dbo.LOBtest WITH (TABLOCKX) SET some_value = some_value - 1; As you might expect, modifying this integer column in 1,000 rows doesn’t take very long, or use many resources.  The STATITICS IO and TIME output shows a total of 9 logical reads, and 25ms elapsed time.  The query plan is also very simple: Looking at the Clustered Index Scan, we can see that SQL Server only retrieves the pk and some_value columns during the scan: The pk column is needed by the Clustered Index Update operator to uniquely identify the row that is being changed.  The some_value column is used by the Compute Scalar to calculate the new value.  (In case you are wondering what the Top operator is for, it is used to enforce SET ROWCOUNT). Test 2: Simple Update with an Index Now let’s create a nonclustered index keyed on the some_value column, with lob_data as an included column: CREATE NONCLUSTERED INDEX [IX dbo.LOBtest some_value (lob_data)] ON dbo.LOBtest (some_value) INCLUDE ( lob_data ) WITH ( FILLFACTOR = 100, MAXDOP = 1, SORT_IN_TEMPDB = ON ); This is not a useful index for our simple update query; imagine that someone else created it for a different purpose.  Let’s run our update query again: UPDATE dbo.LOBtest WITH (TABLOCKX) SET some_value = some_value - 1; We find that it now requires 4,014 logical reads and the elapsed query time has increased to around 100ms.  The extra logical reads (4 per row) are an expected consequence of maintaining the nonclustered index. The query plan is very similar to before (click to enlarge): The Clustered Index Update operator picks up the extra work of maintaining the nonclustered index. The new Compute Scalar operators detect whether the value in the some_value column has actually been changed by the update.  SQL Server may be able to skip maintaining the nonclustered index if the value hasn’t changed (see my previous post on non-updating updates for details).  Our simple query does change the value of some_data in every row, so this optimization doesn’t add any value in this specific case. The output list of columns from the Clustered Index Scan hasn’t changed from the one shown previously: SQL Server still just reads the pk and some_data columns.  Cool. Overall then, adding the nonclustered index hasn’t had any startling effects, and the LOB column data still isn’t being read from the table.  Let’s see what happens if we make the nonclustered index unique. Test 3: Simple Update with a Unique Index Here’s the script to create a new unique index, and drop the old one: CREATE UNIQUE NONCLUSTERED INDEX [UQ dbo.LOBtest some_value (lob_data)] ON dbo.LOBtest (some_value) INCLUDE ( lob_data ) WITH ( FILLFACTOR = 100, MAXDOP = 1, SORT_IN_TEMPDB = ON ); GO DROP INDEX [IX dbo.LOBtest some_value (lob_data)] ON dbo.LOBtest; Remember that SQL Server only enforces uniqueness on index keys (the some_data column).  The lob_data column is simply stored at the leaf-level of the non-clustered index.  With that in mind, we might expect this change to make very little difference.  Let’s see: UPDATE dbo.LOBtest WITH (TABLOCKX) SET some_value = some_value - 1; Whoa!  Now look at the elapsed time and logical reads: Scan count 1, logical reads 2016, physical reads 0, read-ahead reads 0, lob logical reads 36015, lob physical reads 0, lob read-ahead reads 15992.   CPU time = 172 ms, elapsed time = 16172 ms. Even with all the data and index pages in memory, the query took over 16 seconds to update just 1,000 rows, performing over 52,000 LOB logical reads (nearly 16,000 of those using read-ahead). Why on earth is SQL Server reading LOB data in a query that only updates a single integer column? The Query Plan The query plan for test 3 looks a bit more complex than before: In fact, the bottom level is exactly the same as we saw with the non-unique index.  The top level has heaps of new stuff though, which I’ll come to in a moment. You might be expecting to find that the Clustered Index Scan is now reading the lob_data column (for some reason).  After all, we need to explain where all the LOB logical reads are coming from.  Sadly, when we look at the properties of the Clustered Index Scan, we see exactly the same as before: SQL Server is still only reading the pk and some_value columns – so what’s doing the LOB reads? Updates that Sneakily Read Data We have to go as far as the Clustered Index Update operator before we see LOB data in the output list: [Expr1020] is a bit flag added by an earlier Compute Scalar.  It is set true if the some_value column has not been changed (part of the non-updating updates optimization I mentioned earlier). The Clustered Index Update operator adds two new columns: the lob_data column, and some_value_OLD.  The some_value_OLD column, as the name suggests, is the pre-update value of the some_value column.  At this point, the clustered index has already been updated with the new value, but we haven’t touched the nonclustered index yet. An interesting observation here is that the Clustered Index Update operator can read a column into the data flow as part of its update operation.  SQL Server could have read the LOB data as part of the initial Clustered Index Scan, but that would mean carrying the data through all the operations that occur prior to the Clustered Index Update.  The server knows it will have to go back to the clustered index row to update it, so it delays reading the LOB data until then.  Sneaky! Why the LOB Data Is Needed This is all very interesting (I hope), but why is SQL Server reading the LOB data?  For that matter, why does it need to pass the pre-update value of the some_value column out of the Clustered Index Update? The answer relates to the top row of the query plan for test 3.  I’ll reproduce it here for convenience: Notice that this is a wide (per-index) update plan.  SQL Server used a narrow (per-row) update plan in test 2, where the Clustered Index Update took care of maintaining the nonclustered index too.  I’ll talk more about this difference shortly. The Split/Sort/Collapse combination is an optimization, which aims to make per-index update plans more efficient.  It does this by breaking each update into a delete/insert pair, reordering the operations, removing any redundant operations, and finally applying the net effect of all the changes to the nonclustered index. Imagine we had a unique index which currently holds three rows with the values 1, 2, and 3.  If we run a query that adds 1 to each row value, we would end up with values 2, 3, and 4.  The net effect of all the changes is the same as if we simply deleted the value 1, and added a new value 4. By applying net changes, SQL Server can also avoid false unique-key violations.  If we tried to immediately update the value 1 to a 2, it would conflict with the existing value 2 (which would soon be updated to 3 of course) and the query would fail.  You might argue that SQL Server could avoid the uniqueness violation by starting with the highest value (3) and working down.  That’s fine, but it’s not possible to generalize this logic to work with every possible update query. SQL Server has to use a wide update plan if it sees any risk of false uniqueness violations.  It’s worth noting that the logic SQL Server uses to detect whether these violations are possible has definite limits.  As a result, you will often receive a wide update plan, even when you can see that no violations are possible. Another benefit of this optimization is that it includes a sort on the index key as part of its work.  Processing the index changes in index key order promotes sequential I/O against the nonclustered index. A side-effect of all this is that the net changes might include one or more inserts.  In order to insert a new row in the index, SQL Server obviously needs all the columns – the key column and the included LOB column.  This is the reason SQL Server reads the LOB data as part of the Clustered Index Update. In addition, the some_value_OLD column is required by the Split operator (it turns updates into delete/insert pairs).  In order to generate the correct index key delete operation, it needs the old key value. The irony is that in this case the Split/Sort/Collapse optimization is anything but.  Reading all that LOB data is extremely expensive, so it is sad that the current version of SQL Server has no way to avoid it. Finally, for completeness, I should mention that the Filter operator is there to filter out the non-updating updates. Beating the Set-Based Update with a Cursor One situation where SQL Server can see that false unique-key violations aren’t possible is where it can guarantee that only one row is being updated.  Armed with this knowledge, we can write a cursor (or the WHILE-loop equivalent) that updates one row at a time, and so avoids reading the LOB data: SET NOCOUNT ON; SET STATISTICS XML, IO, TIME OFF;   DECLARE @PK INTEGER, @StartTime DATETIME; SET @StartTime = GETUTCDATE();   DECLARE curUpdate CURSOR LOCAL FORWARD_ONLY KEYSET SCROLL_LOCKS FOR SELECT L.pk FROM LOBtest L ORDER BY L.pk ASC;   OPEN curUpdate;   WHILE (1 = 1) BEGIN FETCH NEXT FROM curUpdate INTO @PK;   IF @@FETCH_STATUS = -1 BREAK; IF @@FETCH_STATUS = -2 CONTINUE;   UPDATE dbo.LOBtest SET some_value = some_value - 1 WHERE CURRENT OF curUpdate; END;   CLOSE curUpdate; DEALLOCATE curUpdate;   SELECT DATEDIFF(MILLISECOND, @StartTime, GETUTCDATE()); That completes the update in 1280 milliseconds (remember test 3 took over 16 seconds!) I used the WHERE CURRENT OF syntax there and a KEYSET cursor, just for the fun of it.  One could just as well use a WHERE clause that specified the primary key value instead. Clustered Indexes A clustered index is the ultimate index with included columns: all non-key columns are included columns in a clustered index.  Let’s re-create the test table and data with an updatable primary key, and without any non-clustered indexes: IF OBJECT_ID(N'dbo.LOBtest', N'U') IS NOT NULL DROP TABLE dbo.LOBtest; GO CREATE TABLE dbo.LOBtest ( pk INTEGER NOT NULL, some_value INTEGER NULL, lob_data VARCHAR(MAX) NULL, another_column CHAR(5) NULL, CONSTRAINT [PK dbo.LOBtest pk] PRIMARY KEY CLUSTERED (pk ASC) ); GO DECLARE @Data VARCHAR(MAX); SET @Data = REPLICATE(CONVERT(VARCHAR(MAX), 'x'), 65540);   WITH Numbers (n) AS ( SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 0)) FROM master.sys.columns C1, master.sys.columns C2 ) INSERT LOBtest WITH (TABLOCKX) ( pk, some_value, lob_data ) SELECT TOP (1000) N.n, N.n, @Data FROM Numbers N WHERE N.n <= 1000; Now here’s a query to modify the cluster keys: UPDATE dbo.LOBtest SET pk = pk + 1; The query plan is: As you can see, the Split/Sort/Collapse optimization is present, and we also gain an Eager Table Spool, for Halloween protection.  In addition, SQL Server now has no choice but to read the LOB data in the Clustered Index Scan: The performance is not great, as you might expect (even though there is no non-clustered index to maintain): Table 'LOBtest'. Scan count 1, logical reads 2011, physical reads 0, read-ahead reads 0, lob logical reads 36015, lob physical reads 0, lob read-ahead reads 15992.   Table 'Worktable'. Scan count 1, logical reads 2040, physical reads 0, read-ahead reads 0, lob logical reads 34000, lob physical reads 0, lob read-ahead reads 8000.   SQL Server Execution Times: CPU time = 483 ms, elapsed time = 17884 ms. Notice how the LOB data is read twice: once from the Clustered Index Scan, and again from the work table in tempdb used by the Eager Spool. If you try the same test with a non-unique clustered index (rather than a primary key), you’ll get a much more efficient plan that just passes the cluster key (including uniqueifier) around (no LOB data or other non-key columns): A unique non-clustered index (on a heap) works well too: Both those queries complete in a few tens of milliseconds, with no LOB reads, and just a few thousand logical reads.  (In fact the heap is rather more efficient). There are lots more fun combinations to try that I don’t have space for here. Final Thoughts The behaviour shown in this post is not limited to LOB data by any means.  If the conditions are met, any unique index that has included columns can produce similar behaviour – something to bear in mind when adding large INCLUDE columns to achieve covering queries, perhaps. Paul White Email: [email protected] Twitter: @PaulWhiteNZ

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  • How to pre-configure (configure defaults for new users) KDE?

    - by luxifer
    I'm trying to figure out how to configure KDE for new users. That is: setting up KDE and make these settings default for every user upon her first login. I know that there's /etc/skel but it's not working nicely because KDE writes user- and machine-specific stuff in its users configuration files and I want this to work for every user on every machine. Also modifying stuff in /usr/share seems wrong to me as well as stuff there could get overwritten by an update or - even worse - modifications there could make auto upgrade fail. So, is there a standard way of doing this? Thanks

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  • C# Bind DataTable to Existing DataGridView Column Definitions

    - by Timothy
    I've been struggling with a NullReferenceException and hope someone here will be able to point me in the right direction. I'm trying to create and populate a DataTable and then show the results in a DataGridView control. The basic code follows, and Execution stops with a NullReferenceException at the point where I invoke the new UpdateResults_Delegate. Oddly enough, I can trace entries.Rows.Count successfully before I return it from QueryEventEntries, so I can at least show 1) entries is not a null reference, and 2) the DataTable contains rows of data. I know I have to be doing something wrong, but I just don't know what. private void UpdateResults(DataTable entries) { dataGridView.DataSource = entries; } private void button_Click(object sender, EventArgs e) { PerformQuery(); } private void PerformQuery() { DateTime start = new DateTime(dateTimePicker1.Value.Year, dateTimePicker1.Value.Month, dateTimePicker1.Value.Day, 0, 0, 0); DateTime stop = new DateTime(dateTimePicker2.Value.Year, dateTimePicker2.Value.Month, dateTimePicker2.Value.Day, 0, 0, 0); DataTable entries = QueryEventEntries(start, stop); UpdateResults(entries); } private DataTable QueryEventEntries(DateTime start, DateTime stop) { DataTable entries = new DataTable(); entries.Columns.AddRange(new DataColumn[] { new DataColumn("event_type", typeof(Int32)), new DataColumn("event_time", typeof(DateTime)), new DataColumn("event_detail", typeof(String))}); using (SqlConnection conn = new SqlConnection(DSN)) { using (SqlDataAdapter adapter = new SqlDataAdapter( "SELECT event_type, event_time, event_detail FROM event_log " + "WHERE event_time >= @start AND event_time <= @stop", conn)) { adapter.SelectCommand.Parameters.AddRange(new Object[] { new SqlParameter("@start", start), new SqlParameter("@stop", stop)}); adapter.Fill(entries); } } return entries; } Update I'd like to summarize and provide some additional information I've learned from the discussion here and debugging efforts since I originally posted this question. I am refactoring old code that retrieved records from a database, collected those records as an array, and then later iterated through the array to populate a DataGridView row by row. Threading was originally implemented to compensate and keep the UI responsive during the unnecessary looping. I have since stripped out Thread/Invoke; everything now occurs on the same execution thread (thank you, Sam). I am attempting to replace the slow, unwieldy approach using a DataTable which I can fill with a DataAdapter, and assign to the DataGridView through it's DataSource property (above code updated). I've iterated through the entries DataTable's rows to verify the table contains the expected data before assigning it as the DataGridView's DataSource. foreach (DataRow row in entries.Rows) { System.Diagnostics.Trace.WriteLine( String.Format("{0} {1} {2}", row[0], row[1], row[2])); } One of the column of the DataGridView is a custom DataGridViewColumn to stylize the event_type value. I apologize I didn't mention this before in the original post but I wasn't aware it was important to my problem. I have converted this column temporarily to a standard DataGridViewTextBoxColumn control and am no longer experiencing the Exception. The fields in the DataTable are appended to the list of fields that have been pre-specified in Design view of the DataGridView. The records' values are being populated in these appended fields. When the run time attempts to render the cell a null value is provided (as the value that should be rendered is done so a couple columns over). In light of this, I am re-titling and re-tagging the question. I would still appreciate it if others who have experienced this can instruct me on how to go about binding the DataTable to the existing column definitions of the DataGridView.

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  • If record exists in database, UPDATE a single column

    - by Doug
    I have a bulk uploading object in place that is being used to bulk upload roughly 25-40 image files at a time. Each image is about 100-150 kb in size. During the upload, I've created a for each loop that takes the file name of the image (minus the file extension) to write it into a column named "sku". Also, for each file being uploaded, the date is recorded to a column named DateUpdated, as well as some image path data. Here is my c# code: protected void graphicMultiFileButton_Click(object sender, EventArgs e) { //graphicMultiFile is the ID of the bulk uploading object ( provided by Dean Brettle: http://www.brettle.com/neatupload ) if (graphicMultiFile.Files.Length > 0) { foreach (UploadedFile file in graphicMultiFile.Files) { //strip ".jpg" from file name (will be assigned as SKU) string sku = file.FileName.Substring(0, file.FileName.Length - 4); //assign the directory where the images will be stored on the server string directoryPath = Server.MapPath("~/images/graphicsLib/" + file.FileName); //ensure that if image existes on server that it will get overwritten next time it's uploaded: file.MoveTo(directoryPath, MoveToOptions.Overwrite); //current sql that inserts a record to the db SqlCommand comm; SqlConnection conn; string connectionString = ConfigurationManager.ConnectionStrings["DataConnect"].ConnectionString; conn = new SqlConnection(connectionString); comm = new SqlCommand("INSERT INTO GraphicsLibrary (sku, imagePath, DateUpdated) VALUES (@sku, @imagePath, @DateUpdated)", conn); comm.Parameters.Add("@sku", System.Data.SqlDbType.VarChar, 50); comm.Parameters["@sku"].Value = sku; comm.Parameters.Add("@imagePath", System.Data.SqlDbType.VarChar, 300); comm.Parameters["@imagePath"].Value = "images/graphicsLib/" + file.FileName; comm.Parameters.Add("@DateUpdated", System.Data.SqlDbType.DateTime); comm.Parameters["@DateUpdated"].Value = DateTime.Now; conn.Open(); comm.ExecuteNonQuery(); conn.Close(); } } } After images are uploaded, managers will go back and re-upload images that have previously been uploaded. This is because these product images are always being revised and improved. For each new/improved image, the file name and extension will remain the same - so that when image 321-54321.jpg was first uploaded to the server, the new/improved version of that image will still have the image file name as 321-54321.jpg. I can't say for sure if the file sizes will remain in the 100-150KB range. I'll assume that the image file size will grow eventually. When images get uploaded (again), there of course will be an existing record in the database for that image. What is the best way to: Check the database for the existing record (stored procedure or SqlDataReader or create a DataSet ...?) Then if record exists, simply UPDATE that record so that the DateUpdated column gets today's date. If no record exists, do the INSERT of the record as normal. Things to consider: If the record exists, we'll let the actual image be uploaded. It will simply overwrite the existing image so that the new version gets displayed on the web. We're using SQL Server 2000 on hosted environment (DiscountAsp). I'm programming in C#. The uploading process will be used by about 2 managers a few times a month (each) - which to me is not a allot of usage. Although I'm a jr. developer, I'm guessing that a stored procedure would be the way to go. Just seems more efficient - to do this record check away from the for each loop... but not sure. I'd need extra help writing a sproc, since I don't have too much experience with them. Thank everyone...

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  • Is there a web site where I can paste a SQL Insert statement and have it break it out by column?

    - by Scott Whitlock
    I've been working on an application that has no discernable data access layer, so all the SQL statements are just built up as strings and executed. I'm constantly confronted by very long INSERT statements where I'm trying to figure out what value in the VALUES list matches up with what column in the column name list. I was about to create a little helper application where I could paste in an INSERT statement and have it show me a list of values matched up with the column names, just for debugging, and I thought, "someone else has probably done this already." Does anyone know of a web site where I can just paste in an INSERT statement and have it show me a two column table with column names in the first column and values in the second column?

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  • View all ntext column text in SQL Server Management Studio for SQL CE database

    - by Dave
    I often want to do a "quick check" of the value of a large text column in SQL Server Management Studio (SSMS). The maximum number of characters that SSMS will let you view, in grid results mode, is 65535. (It is even less in text results mode.) Sometimes I need to see something beyond that range. Using SQL Server 2005 databases, I often used the trick of converting it to XML, because SSMS lets you view much larger amounts of text that way: SELECT CONVERT(xml, MyCol) FROM MyTable WHERE ... But now I am using SQL CE, and there is no Xml data type. There is still a "Maximum Characters Retreived XML" value under Options; I suppose this is useful when connecting to other data sources. I know I can just get the full value by running a little console app or something, but is there a way within SSMS to see the entire ntext column value? [Edit] OK, this didn't get much attention the first time around (18 views?!). It's not a huge concern, but maybe I'm just obsessed with it. There has to be some good way around this, doesn't there? So a modest bounty is active. What I am willing to accept as answers, in order from best-to-worst: A solution that works just as easy as the XML trick in SQL CE. That is, a single function (convert, cast, etc.) that does the job. A not-too-invasive way to hack SSMS to get it to display more text in the results. An equivalent SQL query (perhaps something that creatively uses SUBSTRING and generates multiple ad-hoc columns??) to see the results. The solution should work with nvarchar and ntext columns of any length in SQL CE from SSMS. Any ideas?

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