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How to concatenate columns in a Postgres SELECT?
...catenated to NULL is NULL. If NULL values can be involved and the result shall not be NULL, use concat_ws() to concatenate any number of values (Postgres 9.1 or later):
SELECT concat_ws(', ', a, b) AS ab FROM foo;
Or concat() if you don't need separators:
SELECT concat(a, b) AS ab FROM foo;
No...
How to quit scala 2.11.0 REPL?
...
I ran into the same issue on upgrade, just use colon q.
:q
Additionally, exit was deprecated in 2.10.x with sys.exit suggested instead, so this works as well:
sys.exit
As a side note, I think they did this so you can distinguish between exiting the scala console in sbt and exiting sbt its...
How to replace a character by a newline in Vim
...s a newline (more precisely, it’s treated as the input CR). Here’s a small, non-interactive example to illustrate this, using the Vim command line feature (in other words, you can copy and paste the following into a terminal to run it). xxd shows a hexdump of the resulting file.
echo bar > te...
Pointer expressions: *ptr++, *++ptr and ++*ptr
...ting not to the entire string, but only to the first character, 'H'. After all, p is a pointer to one char, not to the entire string. The value of p is the address of the 'H' in "Hello".
Then you set up a loop:
while (*p++)
What does the loop condition *p++ mean? Three things are at work here t...
Logging best practices [closed]
...s until after Filter.ShouldTrace() has succeeded. This means no expensive calls to ToString() on parameter values until after the system has confirmed message will actually be logged.
The Trace.CorrelationManager allows you to correlate log statements about the same logical operation (see below)....
How to make the division of 2 ints produce a float instead of another int?
...ppens before the division.
The other operand will be effectively automatically cast to a float by the compiler because the rules say that if either operand is of floating point type then the operation will be a floating point operation, even if the other operand is integral. Java Language Specific...
Synchronous request in Node.js
If I need to call 3 http API in sequential order, what would be a better alternative to the following code:
18 Answers
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Duplicate symbols for architecture x86_64 under Xcode
...at defines an Objective-C class or category. While this option will
typically result in a larger executable (due to additional object code
loaded into the application), it will allow the successful creation of
effective Objective-C static libraries that contain categories on
existing classes...
What's the difference between EscapeUriString and EscapeDataString?
...)*+,;=
For completeness, the unreserved characters are alphanumeric and -._~
Both methods escape characters that are neither reserved nor unreserved.
I disagree with the general notion that EscapeUriString is evil. I think a method that escapes only illegal characters (such as spaces) and not res...
What is the email subject length limit?
How many characters are allowed to be in the subject line of Internet email?
I had a scan of The RFC for email but could not see specifically how long it was allowed to be.
I have a colleague that wants to programmatically validate for it.
...