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c++ boost::multi_index composite keys efficiency - c++1y / stl - 清泛IT社区,为创新赋能!
...cumentation states that "Composite keys are sorted by lexicographical order, i.e. sorting is performed by the first key, then the second key if the first one is equal, etc". Does this mean that the structure is stored such that a lookup for a specific 2-part composite key will take O(n=1) ...
Sorting data based on second column of a file
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Faced issue with "wrong" ordering. Pay attention to man "*** WARNING *** The locale specified by the environment affects sort order. Set LC_ALL=C to get the traditional sort order that uses native byte values." (for string match case without -n)
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Operator precedence with Javascript Ternary operator
...ach type of operator in a language is evaluated in a particular predefined order (and not just left-to-right).
Reference: Javascript Operator Precedence
How to change the order of evaluation:
Now we know why it fails, you need to know how to make it work.
Some other answers talk about changing t...
Comparing two collections for equality irrespective of the order of items in them
...valent if they
have the same elements in the same
quantity, but in any order. Elements
are equal if their values are equal,
not if they refer to the same object.
Using reflector, I modified the code behind AreEquivalent() to create a corresponding equality comparer. It is more complete tha...
Why can't C compilers rearrange struct members to eliminate alignment padding? [duplicate]
...
There are multiple reasons why the C compiler cannot automatically reorder the fields:
The C compiler doesn't know whether the struct represents the memory structure of objects beyond the current compilation unit (for example: a foreign library, a file on disc, network data, CPU page tables,...
How to get Last record from Sqlite?
...LE);
OR
you can also used following solution:
SELECT * FROM tablename ORDER BY column DESC LIMIT 1;
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MySQL convert date string to Unix timestamp
... After so many trials your solution worked for me: select * from (SELECT order_increment_id, FROM_UNIXTIME(UNIX_TIMESTAMP(STR_TO_DATE(order_date, '%d %M %Y %h:%i:%s %p')),'%Y-%m-%d') as order_date, email_sent FROM `packingslip_header` where email_sent=0) t where order_date >= '2019-11-13' O...
PostgreSQL: Modify OWNER on all tables simultaneously in PostgreSQL
...ROM pg_tables WHERE NOT schemaname IN ('pg_catalog', 'information_schema')
ORDER BY schemaname, tablename;
Sequences
SELECT 'ALTER SEQUENCE '|| sequence_schema || '.' || sequence_name ||' OWNER TO my_new_owner;'
FROM information_schema.sequences WHERE NOT sequence_schema IN ('pg_catalog', 'inform...
Merge and interleave two arrays in Ruby
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This won't give a result array in the order Chris asked for, but if the order of the resulting array doesn't matter, you can just use a |= b. If you don't want to mutate a, you can write a | b and assign the result to a variable.
See the set union documentation ...
GROUP BY with MAX(DATE) [duplicate]
...e FROM (
SELECT train, dest, time,
RANK() OVER (PARTITION BY train ORDER BY time DESC) dest_rank
FROM traintable
) where dest_rank = 1
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