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SQL Server indexes - ascending or descending, what difference does it make?
...TE INDEX ix_index ON mytable (col1, col2 DESC);
can be used for either:
SELECT *
FROM mytable
ORDER BY
col1, col2 DESC
or:
SELECT *
FROM mytable
ORDER BY
col1 DESC, col2
, but not for:
SELECT *
FROM mytable
ORDER BY
col1, col2
An index on a single colum...
Convert data.frame column format from character to factor
...yr::mutate_if() to convert all character columns or dplyr::mutate_at() for select named character columns to factors:
library(dplyr)
# all character columns to factor:
df <- mutate_if(df, is.character, as.factor)
# select character columns 'char1', 'char2', etc. to factor:
df <- mutate_at(d...
How to export data as CSV format from SQL Server using sqlcmd?
...
You can run something like this:
sqlcmd -S MyServer -d myDB -E -Q "select col1, col2, col3 from SomeTable"
-o "MyData.csv" -h-1 -s"," -w 700
-h-1 removes column name headers from the result
-s"," sets the column seperator to ,
-w 700 sets the row width to 700 chars (this will nee...
Do HTML WebSockets maintain an open connection for each client? Does this scale?
... limitation that is usually encountered is the maximum number of file descriptors (sockets consume file descriptors) that can be open simultaneously. This often defaults to 1024 but can easily be configured higher.
Ever tried configuring a web server to support tens of thousands of simultaneous AJA...
Nginx 403 error: directory index of [folder] is forbidden
... rewrite ^/(.+)/$ /$1 permanent;
}
# pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
location ~ \.php$ {
fastcgi_split_path_info ^(.+\.php)(/.+)$;
# # NOTE: You should have "cgi.fix_pathinfo = 0;" in php.ini
# # With php5-fpm:
...
How to use NULL or empty string in SQL
...
Select *
From Table
Where (col is null or col = '')
Or
Select *
From Table
Where IsNull(col, '') = ''
share
|
improve t...
How to color System.out.println output? [duplicate]
...7 | white |
| 39 | 49 | default |
+~~~~~~+~~~~~~+~~~~~~~~~~~+
Select Graphic Rendition (SGR)
SGR just allows you to change the text. Many of these do not work in certain terminals, so use these sparingly in production-level projects. However, they can be useful for making program outpu...
How to check if a particular service is running on Ubuntu
...
For Ubuntu (checked with 12.04)
You can get list of all services and select by color one of them with 'grep':
sudo service --status-all | grep postgres
Or you may use another way if you know correct name of service:
sudo service postgresql status
...
httpd: Could not reliably determine the server's fully qualified domain name, using 127.0.0.1 for Se
...m
Choose an FQDN and include it both in your /etc/hosts file on both the IPv4 and IPv6 addresses you are using (in your case, localhost or 127.0.0.1), and change your ServerName in your httpd configuration to match.
/etc/hosts:
127.0.0.1 localhost.localdomain localhost host.server4-245.com
::...
Windows远程桌面授权错误（授权超时）等报错信息疑难解答 - 更多技术 - 清...
...器可以通讯。要完成上述操作，请在每台计算机上使用 IP 地址、FQDN 和 NetBIOS 名称分别针对其他两台计算机运行ping命令。如果任何ping命令失败，请验证网络上的 DNS 配置。
4. 在终端服务器上，设置一个要连接到的首选授权...