大约有 40,000 项符合查询结果（耗时：0.0368秒） [XML]
postgresql COUNT(DISTINCT …) very slow
...48.07 rows=1 width=4) (actual time=1766.472..1766.472 rows=1 loops=1)
-> Seq Scan on one (cost=0.00..32698.45 rows=1499845 width=4) (actual time=31.371..185.914 rows=1499845 loops=1)
Total runtime: 1766.642 ms
(3 rows)
group by+count(*)
...
What is cardinality in MySQL?
...` (`i`),
KEY `c` (`c`,`i`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1
mysql> select count(distinct c) from antest;
+-------------------+
| count(distinct c) |
+-------------------+
| 101 |
+-------------------+
1 row in set (0.36 sec)
mysql> select count(distinct i) from antest;...
Test if number is odd or even
...) instead of array_search :
$value = "1024";// A Number
$even = array(0 => 1, 2 => 1, 4 => 1, 6 => 1, 8 => 1);
if(isset($even[substr($value, -1)]){
// Even Number
}else{
// Odd Number
}
Or to make it more faster (beats mod operator at times) :
$even = array(0, 2, 4, 6, 8);
if(...
Removing App ID from Developer Connection
...Please check this stack link. we CAN delete the app by . go to AppId Edit > Delete. [1]: stackoverflow.com/a/24008521/2098690
– Esha
Nov 26 '14 at 4:24
...
How do I manually create a file with a . (dot) prefix in Windows? For example, .htaccess
...
If you start Notepad and then File -> Save As -> Write .htaccess and choose "All Files" as the type - then it will create the .htaccess file for you.
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...
What does ||= (or-equals) mean in Ruby?
... not evaluated, and no assignment takes place. For example:
a ||= nil # => nil
a ||= 0 # => 0
a ||= 2 # => 0
foo = false # => false
foo ||= true # => true
foo ||= false # => true
Confusingly, it looks similar to other assignment operators (such as +=), but behaves differently.
...
Visual Studio 2010 annoyingly opens documents in wrong MDI pane
...ry resetting the window layout and see if that fixes it.
First, Window -> Close All Documents
Then, Window -> Reset Window Layout
Exit VS to be sure, then go back in.
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improve this a...
Working with time DURATION, not time of day
...b 1st. You can get this with a formula: =TEXT(A1,"0")&" day"&IF(A1>1,"s "," ")&TEXT(HOUR(A1),"0")&" hours "&MINUTE(A1)&" minutes"
– Peter Albert
Jun 15 '18 at 13:36
...
Why does datetime.datetime.utcnow() not contain timezone information?
...tetime.timezone.utc) does return UTC time with tzinfo set.
So you can do:
>>> import datetime
>>> datetime.datetime.now(datetime.timezone.utc)
datetime.datetime(2014, 7, 10, 2, 43, 55, 230107, tzinfo=datetime.timezone.utc)
...
sqlite3.ProgrammingError: Incorrect number of bindings supplied. The current statement uses 1, and t
...en Python sees that as 74 separate bind values, each one character long.
>>> len(img)
74
>>> len((img,))
1
If you find it easier to read, you can also use a list literal:
cursor.execute('INSERT INTO images VALUES(?)', [img])
...