大约有 800 项符合查询结果（耗时：0.0126秒） [XML]
What is an index in SQL?
...s relevant for other SQL servers as well):
http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html
An index can be used to efficiently find all rows matching some column in your query and then walk through only that subset of the table to find exact matches. If you don't have indexes on any colum...
How can you detect the version of a browser?
...cebook app on Android). The useragent string looks something like: Mozilla/5.0 (Linux; Android 5.0; Nexus 9 Build/LRX21R; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/45.0.2454.95 Safari/537.36 [FB_IAB/FB4A;FBAV/50.0.0.10.54;] This is a very prominent user agent unfortunately so can...
How to reset or change the MySQL root password?
...
Worked with mysql v 5.0 as well... sudo dpkg-reconfigure mysql-server-5.0
– dsghi
Feb 24 '15 at 3:19
...
How to set a default value for a datetime column to record creation time in a migration?
...ere is a sample migration:
class CreatePosts < ActiveRecord::Migration[5.0]
def change
create_table :posts do |t|
t.datetime :modified_at, default: -> { 'CURRENT_TIMESTAMP' }
t.timestamps
end
end
end
See discussion at https://github.com/rails/rails/issues/27077 and ...
Can overridden methods differ in return type?
...
Yes it may differ but their are some limitations.
Before Java 5.0, when you override a method, both parameters and return type must match exactly. In Java 5.0, it introduces a new facility called covariant return type. You can override a method with the same signature but returns a subc...
Xcode 4 - “Valid signing identity not found” error on provisioning profiles on a new Macintosh insta
...port/import sequence.
Picture for XCode 4.6 added by WP
Edit for XCode 5.0 or newer:
Open XCode -> Preferences ('Command' + ',')
Select the Apple ID from the list.
Click on the SETTING icon near the bottom-left corner of window, and choose EXPORT ACCOUNTS... Xcode asks you to choose a file...
How to Detect if I'm Compiling Code with a particular Visual Studio version?
...7 version 15.3)
MSVC++ 14.1 _MSC_VER == 1910 (Visual Studio 2017 version 15.0)
MSVC++ 14.0 _MSC_VER == 1900 (Visual Studio 2015 version 14.0)
MSVC++ 12.0 _MSC_VER == 1800 (Visual Studio 2013 version 12.0)
MSVC++ 11.0 _MSC_VER == 1700 (Visual Studio 2012 version 11.0)
MSVC++ 10.0 _MSC_VER == 160...
How to properly import a selfsigned certificate into Java keystore that is available to all Java app
...
D:\Java\jdk1.5.0_10\bin\keytool -import -file "D:\Certificates\SDS services\Dev\dev-sdsservices-was8.infavig.com.cer" -keystore "D:\Java\jdk1.5.0_10\jre\lib\security\cacerts" -alias "sds certificate"
...
MySQL remove all whitespaces from the entire column
...ol_name` = REPLACE(`col_name`, '\n', '')
http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_replace
To remove first and last space(s) of column :
UPDATE `table` SET `col_name` = TRIM(`col_name`)
http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_trim
...
Flat file databases [closed]
...
SQLite was build into 5.0+ by default, but discountinued (!) from PHP 5.4+ on !!! As I write this in July 2012, SQLite will not work on up-to-date systems anymore by default. Official statement here
– Sliq
Ju...