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What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
The "N+1 selects problem" is generally stated as a problem in Object-Relational mapping (ORM) discussions, and I understand that it has something to do with having to make a lot of database queries for something that seems simple in the object world.
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quick random row selection in Postgres
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You might want to experiment with OFFSET, as in
SELECT myid FROM mytable OFFSET floor(random()*N) LIMIT 1;
The N is the number of rows in mytable. You may need to first do a SELECT COUNT(*) to figure out the value of N.
Update (by Antony Hatchkins)
You must use floor he...
Changing selection in a select with the Chosen plugin
I'm trying to change the currently selected option in a select with the Chosen plugin.
4 Answers
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Getting value of select (dropdown) before change
The thing I want to achieve is whenever the <select> dropdown is changed I want the value of the dropdown before change. I am using 1.3.2 version of jQuery and using on change event but the value I am getting over there is after change.
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In Ruby, is there an Array method that combines 'select' and 'map'?
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I usually use map and compact together along with my selection criteria as a postfix if. compact gets rid of the nils.
jruby-1.5.0 > [1,1,1,2,3,4].map{|n| n*3 if n==1}
=> [3, 3, 3, nil, nil, nil]
jruby-1.5.0 > [1,1,1,2,3,4].map{|n| n*3 if n==1}.compact
=> ...
Convert a list of characters into a string
If I have a list of chars:
9 Answers
9
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Define variable to use with IN operator (T-SQL)
... VALUES (2)
INSERT INTO @MyList VALUES (3)
INSERT INTO @MyList VALUES (4)
SELECT *
FROM MyTable
WHERE MyColumn IN (SELECT Value FROM @MyList)
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Index of Currently Selected Row in DataGridView
It's that simple. How do I get the index of the currently selected Row of a DataGridView ? I don't want the Row object, I want the index (0 .. n).
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Is bool a native C type?
...C90.
Here's a list of keywords in standard C (not C99):
auto
break
case
char
const
continue
default
do
double
else
enum
extern
float
for
goto
if
int
long
register
return
short
signed
static
struct
switch
typedef
union
unsigned
void
volatile
while
Here's an article discussing some other differen...
std::string to float or double
...e temp = winOpacity.toDouble();
Extra note:
If the input data is a const char*, QByteArray::toDouble will be faster.
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