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JPA: How to have one-to-many relation of the same Entity type
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herau
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answered Aug 3 '10 at 4:54
Dan LaRocqueDan LaRocque
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What makes a keychain item unique (in iOS)?
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+50
The primary keys are as follows (derived from open source files from Apple, see Schema.m4, KeySchema.m4 and SecItem.cpp):
For a key...
When do I need to use Begin / End Blocks and the Go keyword in SQL Server?
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MatBailieMatBailie
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Integer division with remainder in JavaScript?
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15 Answers
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What does .SD stand for in data.table in R
...=c(1,3), v=1:6)
setkey(DT, y)
DT
# x y v
# 1: a 1 1
# 2: b 1 3
# 3: c 1 5
# 4: a 3 2
# 5: b 3 4
# 6: c 3 6
Doing this may help you see what .SD is:
DT[ , .SD[ , paste(x, v, sep="", collapse="_")], by=y]
# y V1
# 1: 1 a1_b3_c5
# 2: 3 a2_b4_c6
Basically, the by=y statement breaks the ...
Why and How to avoid Event Handler memory leaks?
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Jon SkeetJon Skeet
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Why does X[Y] join of data.tables not allow a full outer join, or a left join?
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## t b a
## 1: 1 NA 1
## 2: 2 NA 4
## 3: 3 9 9
## 4: 4 16 16
## 5: 5 25 NA
## 6: 6 36 NA
# The following will give the same with the column order X,Y
X[Y[J(unique_keys)]]
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Perl build, unit testing, code coverage: A complete working example
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5 Answers
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What's “wrong” with C++ wchar_t and wstrings? What are some alternatives to wide characters?
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What is wchar_t?
wchar_t is defined such that any locale's char encoding can be converted to a wchar_t representation where every wc...
Element-wise addition of 2 lists?
...> from operator import add
>>> list( map(add, list1, list2) )
[5, 7, 9]
or zip with a list comprehension:
>>> [sum(x) for x in zip(list1, list2)]
[5, 7, 9]
Timing comparisons:
>>> list2 = [4, 5, 6]*10**5
>>> list1 = [1, 2, 3]*10**5
>>> %timeit fr...