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What are bitwise operators?
... several cases.
x << y
is the same as
x * 2y
if you need to quickly multiply by a power of two, but watch out for shifting a 1-bit into the top bit - this makes the number negative unless it's unsigned. It's also useful when dealing with different sizes of data. For example, reading...
SQL Server: What is the difference between CROSS JOIN and FULL OUTER JOIN?
... often faster when there are few matches between the two tables, as use of indexes means it doesn't bother reading all the rows on one of the tables. a full outer join must always read all rows in both tables (or the relevant indexes). In the case where indexes are not enough, or an underlying heap ...
How do you get the list of targets in a makefile?
...al order - i.e.: invoke as make list:
.PHONY: list
list:
@$(MAKE) -pRrq -f $(lastword $(MAKEFILE_LIST)) : 2>/dev/null | awk -v RS= -F: '/^# File/,/^# Finished Make data base/ {if ($$1 !~ "^[#.]") {print $$1}}' | sort | egrep -v -e '^[^[:alnum:]]' -e '^$@$$'
Important: On pasting this, make...
How to get the separate digits of an int number?
...you would like to maintain the order of the digits from least significant (index[0]) to most significant (index[n]), the following updated getDigits() is what you need:
/**
* split an integer into its individual digits
* NOTE: digits order is maintained - i.e. Least significant digit is at index[...
Unique constraint that allows empty values in MySQL
...
Yes, you can do this. See the MySQL reference (version 5.5).
A UNIQUE index creates a constraint such that all values in the index must be distinct. An error occurs if you try to add a new row with a key value that matches an existing row. For all engines, a UNIQUE index allows multiple NULL v...
Trim string in JavaScript?
... this only trims whitespace (newline) .. it does not work like php trim , where you can trim characters as well
– Jeffz
Jun 22 '13 at 20:43
...
Select row with most recent date per user
...posted by Justin, may be more optimal. The accepted answer uses a backward index scan on the primary key of the table, followed by a limit, followed by a sequence scan of the table. Therefore, the accepted answer can be greatly optimized with an additional index. This query could be optimized by an ...
How to get list of all installed packages along with version in composer?
... write this anyone trying to get this using composer.phar and php
– Yashrajsinh Jadeja
Nov 12 '14 at 8:29
9
...
Get list of passed arguments in Windows batch script (.bat)
...
%~dp0 - drive and path to the script (d:\scripts)
%~dpnx0 - is the fully qualified path name of the script (d:\scripts\some-batch.bat)
More info examples at https://www.ss64.com/nt/syntax-args.html and https://www.robvanderwoude.com/parameters.html
...
Python list subtraction operation
...ting and using bisect:
ys = sorted(y)
def bisect_contains(seq, item):
index = bisect.bisect(seq, item)
return index < len(seq) and seq[index] == item
[item for item in x if bisect_contains(ys, item)]
If your items are neither hashable nor comparable, then you're stuck with the quadra...