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What Does Question Mark Mean in Xcode Project Navigator?
... the file and goto Source Control->Add. This will turn ? to A. So, basically: ? means not part of source control. A means added to source control, but not modified. M means it is added to source control and is modified.
– Farhan Hafeez
Feb 13 '13 at 6:44
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Check for installed packages before running install.packages() [duplicate]
...h several users on different computers. One of its lines contains the install.packages("xtable") command.
16 Answers
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Vim - how to run a command immediately when starting vim?
...itializations
9. Read the viminfo file
10. Read the quickfix file
11. Open all windows
12. Execute startup commands
As you can see, your .vimrc will be loaded before plugins. If you put :FindFileCache . in it an error will occur, since that command does not exist yet. (It will exist once the plugi...
Simulate limited bandwidth from within Chrome?
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If you are running Linux, the following command is really useful for this:
trickle -s -d 50 -w 100 firefox
The -s tells the command to run standalone, the -d 50 tells it to limit bandwidth to 50 KB/s, the -w 100 set the peak detection window size to 100 KB. firefox tells the...
Rails extending ActiveRecord::Base
...the ActiveSupport::Concern documentation for more details.
Create a file called active_record_extension.rb in the lib directory.
require 'active_support/concern'
module ActiveRecordExtension
extend ActiveSupport::Concern
# add your instance methods here
def foo
"foo"
end
# add y...
Android add placeholder text to EditText
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Thanks! I didn't know what they call it in android, I just know that on iOS it's called placeholder.
– Mona
Nov 22 '11 at 4:24
40
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Difference between Key, Primary Key, Unique Key and Index in MySQL
...would use indexes to improve the speed of data retrieval. An index is typically created on columns used in JOIN, WHERE, and ORDER BY clauses.
Imagine you have a table called users and you want to search for all the users which have the last name 'Smith'. Without an index, the database would have t...
What are the disadvantages of using persistent connection in PDO
... parent process to let the connection die when the script terminates abnormally.
If the dead script locked tables, those tables will remain locked until the connection dies or the next script that gets the connection unlocks the tables itself.
If the dead script was in the middle of a transaction,...
Can a foreign key be NULL and/or duplicate?
...at field must exist first in a different table (the parent table). That is all an FK is by definition. Null by definition is not a value. Null means that we do not yet know what the value is.
Let me give you a real life example. Suppose you have a database that stores sales proposals. Suppose furth...
How to impose maxlength on textArea in HTML using JavaScript
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@JoshStodola - Indeed you cannot. It would really annoy me as a user if I had pasted a whole piece of something in a textarea, clicked submit, and only saw a small portion of it go through without any response.
– Travis J
Apr 30 '1...