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How to create an object for a Django model with a many to many field?
...fetch the two Bars, we save two SELECT statements, resulting in a total of 5:
INSERT INTO "app_foo" ("name") VALUES ()
SELECT "app_foo_bars"."id", "app_foo_bars"."foo_id", "app_foo_bars"."bar_id" FROM "app_foo_bars" WHERE "app_foo_bars"."foo_id" = 1
SELECT "app_foo_bars"."bar_id" FROM "app_foo_bars...
What does the thread_local mean in C++11?
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155
Thread-local storage duration is a term used to refer to data that is seemingly global or stati...
Transaction isolation levels relation with locks on table
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159
I want to understand the lock each transaction isolation takes on the table
For example, y...
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...
Integer division with remainder in JavaScript?
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15 Answers
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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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Why and How to avoid Event Handler memory leaks?
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Jon SkeetJon Skeet
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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 does X[Y] join of data.tables not allow a full outer join, or a left join?
...]]
## 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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