Wednesday 12 September 2018

Finding duplicate values in MySQL

Do a SELECT with a GROUP BY clause. Let's say name is the column you want to find duplicates in:
SELECT name, COUNT(*) c FROM table GROUP BY name HAVING c > 1;
This will return a result with the name value in the first column, and a count of how many times that value appears in the second

How do I escape ampersands in batch files?

How do I escape ampersands in a batch file (or from the Windows command line) in order to use the start command to open web pages with ampersands in the URL?
Double quotes will not work with start; this starts a new command-line window instead.
Update 1: Wael Dalloul's solution works. In addition, if there are URL encoded characters (e.g. space is encoded as %20) in the URL and it is in a batch file then '%' must be encoded as '%%'. This is not the case in the example.
Example, from the command line (CMD.EXE):
start http://www.google.com/search?client=opera&rls=en&q=escape+ampersand&sourceid=opera&ie=utf-8&oe=utf-8
will result in
http://www.google.com/search?client=opera 
being opened in the default browser and these errors in the command line window:
'rls' is not recognized as an internal or external command,
operable program or batch file.
'q' is not recognized as an internal or external command,
operable program or batch file.
'sourceid' is not recognized as an internal or external command,
operable program or batch file.
'ie' is not recognized as an internal or external command,
operable program or batch file.
'oe' is not recognized as an internal or external command,
operable program or batch file.
Platform: Windows XP 64 bit SP2.



From a cmd:
  • & is escaped like this: ^& (based on @Wael Dalloul's answer)
  • % does not need to be escaped
An example:
start http://www.google.com/search?client=opera^&rls=en^&q=escape+ampersand%20and%20percentage+in+cmd^&sourceid=opera^&ie=utf-8^&oe=utf-8
From a batch file
  • & is escaped like this: ^& (based on @Wael Dalloul's answer)
  • % is escaped like this: %% (based on the OPs update)
An example:
start http://www.google.com/search?client=opera^&rls=en^&q=escape+ampersand%%20and%%20percentage+in+batch+file^&sourceid=opera^&ie=utf-8^&oe=utf-8