大约有 2,300 项符合查询结果（耗时：0.0178秒） [XML]
SQL query for finding records where count > 1
...p int(11) not null,
dt date not null
);
insert into payment values
(1,123,55555,'2009-12-12'),
(1,123,66666,'2009-12-12'),
(1,123,77777,'2009-12-13'),
(2,456,77777,'2009-12-14'),
(2,456,77777,'2009-12-14'),
(2,789,77777,'2009-12-14'),
(2,789,77777,'2009-12-14');
select foo.user_id, foo.cnt fro...
What does the “yield” keyword do?
...one, etc. And generators return... well that's where yield comes in:
def f123():
yield 1
yield 2
yield 3
for item in f123():
print item
Instead of yield statements, if you had three return statements in f123() only the first would get executed, and the function would exit. But f1...
Remove duplicated rows using dplyr
...ction for this purpose.
Original answer below:
library(dplyr)
set.seed(123)
df <- data.frame(
x = sample(0:1, 10, replace = T),
y = sample(0:1, 10, replace = T),
z = 1:10
)
One approach would be to group, and then only keep the first row:
df %>% group_by(x, y) %>% filter(row_nu...
Checking if a string can be converted to float in Python
... ------------
print(isfloat("")) False
print(isfloat("1234567")) True
print(isfloat("NaN")) True nan is also float
print(isfloat("NaNananana BATMAN")) False
print(isfloat("123.456")) True
print(isfloat("123.E4")) ...
Lua简明教程 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...行的字符串）
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a = 'alo\n123"'
a = "alo\n123\""
a = '\97lo\10\04923"'
a = [[alo
123"]]
C语言中的NULL在Lua中是nil，比如你访问一个没有声明过的变量，就是nil，比如下面的v的值就是nil
...
Dynamic SQL - EXEC(@SQL) versus EXEC SP_EXECUTESQL(@SQL)
...
EXEC('SELECT * FROM FOO WHERE ID=?', 123) will replace the parameter placeholder "?" with the value 123 and then execute the query, returning a result for SELECT * FROM FOO WHERE ID=123
– Peter Wone
Jun 1 '10 at 23:27
...
sed: print only matching group
...it with a 2nd grep.
# To extract \1 from /xx([0-9]+)yy/
$ echo "aa678bb xx123yy xx4yy aa42 aa9bb" | grep -Eo 'xx[0-9]+yy' | grep -Eo '[0-9]+'
123
4
# To extract \1 from /a([0-9]+)b/
$ echo "aa678bb xx123yy xx4yy aa42 aa9bb" | grep -Eo 'a[0-9]+b' | grep -Eo '[0-9]+'
678
9
...
module.exports vs exports in Node.js
...:
var x = require('file1.js');
contents of file1.js:
module.exports = '123';
When the above statement is executed, a Module object is created. Its constructor function is:
function Module(id, parent) {
this.id = id;
this.exports = {};
this.parent = parent;
if (parent &&...
What's the difference between Task.Start/Wait and Async/Await?
...Thread.Sleep(1000);
WriteOutput("B - Completed something");
return 123;
}
static void WriteOutput(string message)
{
Console.WriteLine("[{0}] {1}", Thread.CurrentThread.ManagedThreadId, message);
}
DoAsTask Output:
[1] Program Begin
[1] 1 - Starting
[1] 2 - Task started
[3] A - Start...
Regex Named Groups in Java
...atching Strings with Balanced Parentheses slide)
Example:
String:
"TEST 123"
RegExp:
"(?<login>\\w+) (?<id>\\d+)"
Access
matcher.group(1) ==> TEST
matcher.group("login") ==> TEST
matcher.name(1) ==> login
Replace
matcher.replaceAll("aaaaa_$1_sssss_$2____") ==> aaa...