大约有 45,000 项符合查询结果（耗时：0.0715秒） [XML]
Is there a way to 'uniq' by column?
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sort -u -t, -k1,1 file
-u for unique
-t, so comma is the delimiter
-k1,1 for the key field 1
Test result:
overflow@domain2.com,2009-11-27 00:58:29.793000000,xx3.net,255.255.255.0
stack2@domain.com,2009-11-27 01:05:47.893000000,xx2.n...
Add new row to dataframe, at specific row-index, not appended?
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159
Here's a solution that avoids the (often slow) rbind call:
existingDF <- as.data.frame(mat...
Why does this go into an infinite loop?
...ent(MutableInt x) {
int valueBeforeIncrement = x.intValue();
x.add(1);
return new MutableInt(valueBeforeIncrement);
}
Right? Increment the value passed and return the original value: that's the definition of the postincrement operator.
Now, let's see how this behavior plays out in you...
Insert a line at specific line number with sed or awk
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edited Nov 9 '14 at 0:18
answered Jun 30 '11 at 15:54
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How to round the minute of a datetime object
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17 Answers
17
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COUNT(*) vs. COUNT(1) vs. COUNT(pk): which is better? [duplicate]
...T(tableHere) or COUNT(tableHere.*), use that.
In short, don't use COUNT(1) for anything. It's a one-trick pony, which rarely does what you want, and in those rare cases is equivalent to count(*)
Use count(*) for counting
Use * for all your queries that need to count everything, even for joins, ...
Rename Pandas DataFrame Index
...ut with df.rename() only the column name is renamed. Bug? I'm on version 0.12.0
9 Answers
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MySQL: What's the difference between float and double?
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106
They both represent floating point numbers. A FLOAT is for single-precision, while a DOUBLE is...