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What are the differences between a clustered and a non-clustered index?
...than a clustered index
Both types of index will improve performance when select data with fields that use the index but will slow down update and insert operations.
Because of the slower insert and update clustered indexes should be set on a field that is normally incremental ie Id or Timestamp.
...
Select rows of a matrix that meet a condition
...20, ncol = 4)
colnames(m) <- letters[1:4]
The following command will select the first row of the matrix above.
subset(m, m[,4] == 16)
And this will select the last three.
subset(m, m[,4] > 17)
The result will be a matrix in both cases.
If you want to use column names to select columns...
Replace all non-alphanumeric characters in a string
I have a string with which i want to replace any character that isn't a standard character or number such as (a-z or 0-9) with an asterisk. For example, "h^&ell`.,|o w]{+orld" is replaced with "h*ell*o*w*orld". Note that multiple characters such as "^&" get replaced with one asterisk. How would I go...
iOS 7 - Failing to instantiate default view controller
...ard, click anywhere in the white area and press command-a, then command-c (select all and copy)
Open your new storyboard and press command-v to paste the same exact setup
Go to your project settings, change your "Main Interface" to the new Main_iPhoneV2 (If it's your iPad and you're writing a univer...
How can I resolve “Error: No developer directory found at /Developer”?
...
sudo xcode-select -switch /Applications/Xcode.app/Contents/Developer
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HTML for the Pause symbol in audio and video control
...y default) in order to instruct the parser how to transform the bytes into characters correctly. <meta charset="utf-8"/> should be used immediately after <head> in a HTML file, and make sure the correct HTTP headers Content-Type: text/html; charset=utf-8 are set.
Examples:
HTML
&...
What's the difference between MyISAM and InnoDB? [duplicate]
... on the table, and while that lock is held, no other session can perform a SELECT or a DML operation on the table.
Those two specific engines you asked about (InnoDB and MyISAM) have different design goals. MySQL also has other storage engines, with their own design goals.
So, in choosing between In...
SQL-Server: Is there a SQL script that I can use to determine the progress of a SQL Server backup or
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I found this sample script here that seems to be working pretty well:
SELECT r.session_id,r.command,CONVERT(NUMERIC(6,2),r.percent_complete)
AS [Percent Complete],CONVERT(VARCHAR(20),DATEADD(ms,r.estimated_completion_time,GetDate()),20) AS [ETA Completion Time],
CONVERT(NUMERIC(10,2),r.total_el...
SQL Server Management Studio, how to get execution time down to milliseconds
...able in your proc:
DECLARE @EndTime datetime
DECLARE @StartTime datetime
SELECT @StartTime=GETDATE()
-- Write Your Query
SELECT @EndTime=GETDATE()
--This will return execution time of your query
SELECT DATEDIFF(ms,@StartTime,@EndTime) AS [Duration in millisecs]
AND see this
Measuring Quer...
How to get a substring of text?
I have text with length ~700. How do I get only ~30 of its first characters?
5 Answers
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