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What is the difference between square brackets and parentheses in a regex?
...nt, you would code (?:7|8|9) to make it a non capturing group.
[abc] is a "character class" that means "any character from a,b or c" (a character class may use ranges, e.g. [a-d] = [abcd])
The reason these regexes are similar is that a character class is a shorthand for an "or" (but only for singl...
LEFT OUTER joins in Rails 3
...OUTER JOIN users ON users.id = posts.user_id").
joins(:blog).select
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MySQL get the date n days ago as a timestamp
...
DATE_SUB will do part of it depending on what you want
mysql> SELECT DATE_SUB(NOW(), INTERVAL 30 day);
2009-06-07 21:55:09
mysql> SELECT TIMESTAMP(DATE_SUB(NOW(), INTERVAL 30 day));
2009-06-07 21:55:09
mysql> SELECT UNIX_TIMESTAMP(DATE_SUB(NOW(), INTERVAL 30 day));
1244433347
...
How to drop a PostgreSQL database if there are active connections to it?
...Query pg_stat_activity and get the pid values you want to kill, then issue SELECT pg_terminate_backend(pid int) to them.
PostgreSQL 9.2 and above:
SELECT pg_terminate_backend(pg_stat_activity.pid)
FROM pg_stat_activity
WHERE pg_stat_activity.datname = 'TARGET_DB' -- ← change this to your DB
AN...
Tree view of a directory/folder in Windows? [closed]
...all descending files & folders.
In File Explorer under Windows 8.1:
Select folder
Press Shift, right-click mouse, and select "Open command window here"
Type tree /f > tree.txt and press Enter
Use MS Word to open "tree.txt"
The dialog box "File Conversion - tree.txt" will open
For "Text enc...
Equivalent of *Nix 'which' command in PowerShell?
...or of giving you the path you'll need to pipe the output of get-command to select -expandproperty Path.
– Casey
Jul 29 '15 at 12:37
6
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Parse JSON in TSQL
...ing
The article and code is here: Consuming Json strings in SQL server.
Select * from parseJSON('{
"Person":
{
"firstName": "John",
"lastName": "Smith",
"age": 25,
"Address":
{
"streetAddress":"21 2nd Street",
"city":"New York",
"state":"NY",
...
Default filter in Django admin
...lookup, title in self.lookup_choices:
yield {
'selected': self.value() == lookup,
'query_string': cl.get_query_string({
self.parameter_name: lookup,
}, []),
'display': title,
}
def querys...
Can you organize imports for an entire project in eclipse with a keystroke?
...
Select the project in the package explorer and press Ctrl + Shift + O (same keystroke as the single class version). Should work for packages, etc.
s...
Is “else if” a single keyword?
...s section on keywords.
The grammar in section 6.4 also makes this clear:
selection-statement:
if ( condition ) statement
if ( condition ) statement else statement
The if in else if is a statement following the else term. The section also says:
[...]The substatement in a selection-statement...