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Compiler Ambiguous invocation error - anonymous method and method group with Func or Action
... the conversion will succeed without error.
This line is fascinating. It means that there are implicit conversions which exist, but which are subject to being turned into errors! This is a bizarre rule of C#. To digress a moment, here's an example:
void Q(Expression<Func<string>> f){}...
DISTINCT for only one column
... Server 2005 or above use this:
SELECT *
FROM (
SELECT ID,
Email,
ProductName,
ProductModel,
ROW_NUMBER() OVER(PARTITION BY Email ORDER BY ID DESC) rn
FROM Produ...
How do I find a default constraint using INFORMATION_SCHEMA?
...l_columns
INNER JOIN
sys.tables
ON all_columns.object_id = tables.object_id
INNER JOIN
sys.schemas
ON tables.schema_id = schemas.schema_id
INNER JOIN
sys.default_constraints
ON all_columns.default_object_id = default_constraints.object_...
Can't connect to MySQL server error 111 [closed]
...
It probably means that your MySQL server is only listening the localhost interface.
If you have lines like this :
bind-address = 127.0.0.1
In your my.cnf configuration file, you should comment them (add a # at the beginning of the li...
Does pandas iterrows have performance issues?
...and thus very fast. A pandas DataFrame is a "column-oriented table", which means that each column is really just an array. So the native actions you can perform on a DataFrame (like summing all the elements in a column) are going to have few cache misses.
More opportunities for parallelism: A simple...
What does (x ^ 0x1) != 0 mean?
...
The XOR operation (x ^ 0x1) inverts bit 0. So the expression effectively means: if bit 0 of x is 0, or any other bit of x is 1, then the expression is true.
Conversely the expression is false if x == 1.
So the test is the same as:
if (x != 1)
and is therefore (arguably) unnecessarily obfuscat...
Is 161803398 A 'Special' Number? Inside of Math.Random()
...r any integer N, the value N/phi-int(N/phi) >= 1/N/sqrt(5). That would mean that even if one generated a sequence of numbers N/phi-int(N/phi), the distance between the the closest pair will be within a factor of sqrt(5) of the largest possible uniform spacing in the interval (0..1)
...
What is the difference between association, aggregation and composition?
...d as association..
Aggregation and Composition are subsets of association meaning they are specific cases of association.
In both aggregation and composition object of one class "owns" object of another class.
But there is a subtle difference. In Composition the object of class that is owned by...
returning a Void object
...tion. It is better to return a much more constrained type that conveys the meaning much clearer. Having something that returns an Optional<Void> is unnecessary for the same reason that you give, you always get an Optional<Void> that is empty and so all the other methods are pointless. Th...
SQLAlchemy IN clause
...
How about
session.query(MyUserClass).filter(MyUserClass.id.in_((123,456))).all()
edit: Without the ORM, it would be
session.execute(
select(
[MyUserTable.c.id, MyUserTable.c.name],
MyUserTable.c.id.in_((123, 456))
)
).fetchall()
select() takes two pa...