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Can I have multiple primary keys in a single table?
...,'lax'),('mammal','whale'),
('bird','ostrich');
SELECT * FROM animals ORDER BY grp,id;
Which returns:
+--------+----+---------+
| grp | id | name |
+--------+----+---------+
| fish | 1 | lax |
| mammal | 1 | dog |
| mammal | 2 | cat |
| mammal | 3 | whale |
| bird ...
Advantages and disadvantages of GUID / UUID database keys
...a clash.
Disadvantages:
Larger space use, but space is cheap(er)
Can't order by ID to get the insert order.
Can look ugly in a URL, but really, WTF are you doing putting a REAL DB key in a URL!? (This point disputed in comments below)
Harder to do manual debugging, but not that hard.
Personall...
What does the “__block” keyword mean?
...
It tells the compiler that any variable marked by it must be treated in a special way when it is used inside a block. Normally, variables and their contents that are also used in blocks are copied, thus any modification done to these variables don't show outside the block...
How to add external library in IntelliJ IDEA?
...have a smaller
screen like me, you may have to drag resize to the right in order to
see it)
From the dropdown of Add options, choose "Library". A "Choose
Libraries" dialog will appear.
Press "New Library..."
Choose a suitable title for the library
Press "Attach Classes..."
Choose the Jar from your l...
How do I sort a list by different parameters at different timed
...esult, which is the idea of decending (the opposite of the usual ascending order), while leaving it as zero if they were equal.
– Yishai
Dec 4 '13 at 14:05
5
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How to elegantly check if a number is within a range?
...
As others said, use a simple if.
You should think about the ordering.
e.g
1 <= x && x <= 100
is easier to read than
x >= 1 && x <= 100
share
|
impro...
Best way to merge two maps and sum the values of same key?
...mutable.Map[Int,Int] = Map(1 -> 109, 3 -> 300, 2 -> 20)
Specifically, the binary operator for Map[K, V] combines the keys of the maps, folding V's semigroup operator over any duplicate values. The standard semigroup for Int uses the addition operator, so you get the sum of values for eac...
Group by multiple columns in dplyr, using string vector input
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Does the call to one_of() do anything here? I think it is redundant in this context, as the expression is wrapped in a call to vars().
– knowah
Aug 15 '19 at 14:13
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Mongoose populate after save
I cannot manually or automatically populate the creator field on a newly saved object ... the only way I can find is to re-query for the objects I already have which I would hate to do.
...
How is the default submit button on an HTML form determined?
...A form element's default button is the
first submit button in
tree order whose form owner is that
form element.
If the user agent supports letting the user submit a form
implicitly (for example, on some platforms hitting the "enter" key
while a text field is focused implicit...