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What's wrong with nullable columns in composite primary keys?
...s version the "ext" part of the tuple is NOT NULL but defaults to an empty string -- which is semantically (and practically) different from a NULL. A NULL is an unknown, whereas an empty string is a deliberate record of "something not being present". In other words, "empty" and "null" are different ...
Using union and order by clause in mysql
...organize.
But this way has the advantage of being fast, not introducing extra variables, and making it easy to separate out each query including the sort. The ability to add a limit is simply an extra bonus.
And of course feel free to turn the union all into a union and add a sort for the whole...
How are software license keys generated?
...t a matter of making up an algorithm for which CD keys (which could be any string) are easy to generate and easy to verify, but the ratio of valid-CD-keys to invalid-CD-keys is so small that randomly guessing CD keys is unlikely to get you a valid one.
INCORRECT WAY TO DO IT:
Starcraft and Half-li...
No submodule mapping found in .gitmodule for a path that's not a submodule
...
in the file .gitmodules, I replaced string
"path = thirdsrc\boost"
with
"path = thirdsrc/boost",
and it solved! - -
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Use of alloc init instead of new
...selected ones are:
new doesn't support custom initializers (like initWithString)
alloc-init is more explicit than new
General opinion seems to be that you should use whatever you're comfortable with.
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Disabling swap files creation in vim
...ing which is a large part of vim use for a lot of people, it seems like an extra bookeeping job better left out. I personally prefer for all jobs to just have no swaps or other auto-backups. If I really need to develop something, I'd rather have a more high level framework to protect me, preferably ...
RabbitMQ and relationship between channel and connection
... a Channel are serialized, with only one thread being able to run a
command on the Channel at a time. Even so, applications should prefer
using a Channel per thread instead of sharing the same Channel across
multiple threads.
There is no direct relation between Channel and Queue. A Channel ...
What is a good reason to use SQL views?
... T_NEW) but one that has data for both active and inactive users, with one extra column active.
If your system(s) have gazillion queries that do SELECT whatever FROM T_OLD WHERE whatever, you have two choices for the roll-out:
1) Cold Turkey - Change the DB, and at the same time, change, test and ...
Determine the data types of a data frame's columns
...integer" "logical" "factor"
Using str() gets you that information plus extra goodies (such as the levels of your factors and the first few values of each variable):
str(my.data)
'data.frame': 5 obs. of 4 variables:
$ y : num 1.03 1.599 -0.818 0.872 -2.682
$ x1: int 1 2 3 4 5
$ x2: logi T...
What is JavaScript garbage collection?
...called a "scavenger". A scavenger
may refer to a number, an object, a
string, whatever. We maintain a list
of scavengers -- variables are moved
on to the scav list when they come
into scope and off the scav list when
they go out of scope.
Every now and then the garbage
collector ru...