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COUNT(*) vs. COUNT(1) vs. COUNT(pk): which is better? [duplicate]
...e on subordinate.boss_id = boss.boss_id
GROUP BY boss.id
So what's the meaning of COUNT(1) here?
SELECT boss.boss_id, COUNT(1)
FROM boss
LEFT JOIN subordinate on subordinate.boss_id = boss.boss_id
GROUP BY boss.id
Is it this...?
-- counting all the subordinates only
SELECT boss.boss_id, COUNT(...
How can a string be initialized using “ ”?
...d in the call stack, which require less storage spaces and are cheaper to manipulate. On the other hand, objects are stored in the program heap, which require complex memory management and more storage spaces.
For performance reason, Java's String is designed to be in between a primitive and a ...
Why should I declare a virtual destructor for an abstract class in C++?
... edited Aug 19 '16 at 10:37
Daniel Kamil Kozar
15k44 gold badges4040 silver badges6060 bronze badges
answered Nov 7 '08 at 1:01
...
How to get year, month, day, hours, minutes, seconds and milliseconds of the current moment in Java?
...s at the LocalDateTime.parse( "2018-12-25T00:00:00" ). That value has no meaning until you apply a time zone (a ZoneId) to get a ZonedDateTime. Christmas happens first in Kiribati, then later in New Zealand and far east Asia. Hours later Christmas starts in India. More hour later in Africa & Eur...
Any way to delete in vim without overwriting your last yank? [duplicate]
I love vim, but one common gotcha is:
13 Answers
13
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Amazon SimpleDB vs Amazon DynamoDB
...ocument Database on AWS.
SimpleDb is no longer really "iterated on". Meaning that there is no
new development in the future for simpledb. It is "maintained and
supported", but it won't be getting any better.
share
...
How to import a class from default package
...ed Sep 29 '16 at 9:38
Mohammad BanisaeidMohammad Banisaeid
1,5101818 silver badges2929 bronze badges
...
Semaphore vs. Monitors - what's the difference?
...lly when the monitor operation is completed.
A monitor has a built-in mechanism for condition synchronisation in the form of condition variable before proceeding. If the condition is not satisfied, the process has to wait until it is notified of a change in the condition. When a process is waiting ...
How to reverse a singly linked list using only two pointers?
I wonder if there exists some logic to reverse a singly-linked list using only two pointers.
33 Answers
...
Is D a credible alternative to Java and C++? [closed]
...as for C++, while most agree the language is too complex, thousands of companies are successfully using C++ as part of a healthy mix of languages by allowing only a smaller, well-defined subset of the language. It's still hard to beat C++ when both raw performance and small memory usage are require...