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Postgres: Distinct but only for one column
... to order:
select distinct on (name)
name, col1, col2
from names
order by name, col1
Will return the first row when ordered by col1.
distinct on:
SELECT DISTINCT ON ( expression [, ...] ) keeps only the first row of each set of rows where the given expressions evaluate to equal. The DISTINCT O...
Sort a list by multiple attributes?
...swered Nov 20 '10 at 15:32
Mark ByersMark Byers
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扩展App Inventor：具有多点触控和手势检测功能
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What are the rules about using an underscore in a C++ identifier?
...on macros:
identifiers beginning with an underscore followed immediately by an uppercase letter
identifiers containing adjacent underscores (or "double underscore")
Reserved in the global namespace:
identifiers beginning with an underscore
Also, everything in the std namespace is reserved. (Yo...
lexers vs parsers
.... But it
has to be of symbols which are atomic for the language
understood by parser/lexer.
Symbols for the lexer: ASCII characters.
Symbols for the parser: the particular tokens, which are terminal symbols of their grammar.
They analyse these symbols and try to match them with the grammar of the l...
How do I import CSV file into a MySQL table?
... database:
mysqlimport --ignore-lines=1 \
--fields-terminated-by=, \
--local -u root \
-p Database \
TableName.csv
I found it at http://chriseiffel.com/everything-linux/how-to-import-a-large-csv-file-to-mysql/
To make the delimiter a tab, use --fi...
How to sort a dataframe by multiple column(s)
I want to sort a data.frame by multiple columns. For example, with the data.frame below I would like to sort by column z (descending) then by column b (ascending):
...
Delete all documents from index/type without deleting type
I know one can delete all documents from a certain type via deleteByQuery.
15 Answers
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Is it more efficient to copy a vector by reserving and copying, or by creating and swapping? [duplic
...
Your second example does not work if you send the argument by reference. Did you mean
void copyVecFast(vec<int> original) // no reference
{
vector<int> new_;
new_.swap(original);
}
That would work, but an easier way is
vector<int> new_(original);
...
Which is better option to use for dividing an integer number by 2?
...ich of the following techniques is the best option for dividing an integer by 2 and why?
23 Answers
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