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Difference between EXISTS and IN in SQL?
... will tell you whether a query returned any results. e.g.:
SELECT *
FROM Orders o
WHERE EXISTS (
SELECT *
FROM Products p
WHERE p.ProductNumber = o.ProductNumber)
IN is used to compare one value to several, and can use literal values, like this:
SELECT *
FROM Orders
WHERE Produ...
Do try/catch blocks hurt performance when exceptions are not thrown?
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Can you try them in reverse order as well to be sure that JIT compilation hasn't had an effect on the former?
– JoshJordan
Aug 20 '09 at 20:04
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How can I include a YAML file inside another?
... consume an inordinate amount of time because of recursive search.
In order to enable recursive argument, we shall write the !include tag in Mapping or Sequence mode:
Arguments in Sequence mode:
!include [tests/data/include.d/**/*.yaml, true]
Arguments in Mapping mode:
!include {pathna...
How do I set the UI language in vim?
...ystem, but with German semantics for letters, except that the default sort order is ASCIIbetical (ie. sort by codepoint, not according to language conventions). You could use a different variation; see man 7 locale for more.
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How to verify if a file exists in a batch file?
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Multiple variables in a 'with' statement?
... differs from the standard nested with blocks. The managers are created in order before entering the with blocks: m1, m2, m3 = A(), B(), C() If B() or C() fails with exception, then your only hope of properly finalizing A() is the garbage collector.
– Rafał Dowgird
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Ways to implement data versioning in MongoDB
..., content: "bar" }
]
}
data contains all versions. The data array is ordered, new versions will only get $pushed to the end of the array. data.vid is the version id, which is an incrementing number.
Get the most recent version:
find(
{ "_id":ObjectId("...") },
{ "data":{ $slice:-1 } ...
How exactly does the callstack work?
...called function prologue and epilogue, respectively.
Inside the frame the order of the variables is completely unspecified; Compilers "reorder" the positions of local variables inside a frame appropriately to optimize their alignment so the processor can fetch them as quickly as possible. The cruci...
Delete column from pandas DataFrame
...das has a quite wildly grown architecture that needs to be reconsidered in order for this kind of cognitive dissonance not to occur to its users.
Protip:
Don't use df.column_name, It may be pretty, but it causes cognitive dissonance
Zen of Python quotes that fits in here:
There are multiple ways of ...
How to import the class within the same directory or sub directory?
...
I just learned (thanks to martineau's comment) that, in order to import classes from files within the same directory, you would now write in Python 3:
from .user import User
from .dir import Dir
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