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MySQL select 10 random rows from 600K rows fast
How can I best write a query that selects 10 rows randomly from a total of 600k?
26 Answers
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On select change, get data attribute value
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You need to find the selected option:
$(this).find(':selected').data('id')
or
$(this).find(':selected').attr('data-id')
although the first method is preferred.
shar...
What is a unix command for deleting the first N characters of a line?
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Use cut. Eg. to strip the first 4 characters of each line (i.e. start on the 5th char):
tail -f logfile | grep org.springframework | cut -c 5-
share
|
impr...
C++ where to initialize static const
... static const string s; // Can never be initialized here.
static const char* cs; // Same with C strings.
static const int i = 3; // Integral types can be initialized here (*)...
static const int j; // ... OR in cpp.
};
foo.cpp
#include "foo.h"
const string foo::s = "foo string";
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How to select unique records by SQL
When I perform "SELECT * FROM table" I got results like below:
8 Answers
8
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How do I create a Java string from the contents of a file?
...eserving line terminators:
String content = Files.readString(path, StandardCharsets.US_ASCII);
For versions between Java 7 and 11, here's a compact, robust idiom, wrapped up in a utility method:
static String readFile(String path, Charset encoding)
throws IOException
{
byte[] encoded = Files.re...
Escape double quotes in parameter
...ve all the quotes here and place the parameter value in a string used in a select query filter? Can someone help?
– SFDC_Learner
Nov 24 '15 at 16:21
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When should I use cross apply over inner join?
...APPLY works better on things that have no simple JOIN condition.
This one selects 3 last records from t2 for each record from t1:
SELECT t1.*, t2o.*
FROM t1
CROSS APPLY
(
SELECT TOP 3 *
FROM t2
WHERE t2.t1_id = t1.id
ORDER BY
t2.ran...
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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How to see if an object is an array without using reflection?
...d have to check if the object is an instanceof boolean[], byte[], short[], char[], int[], long[], float[], double[], or Object[], if you want to detect all array types.
Also, an int[][] is an instanceof Object[], so depending on how you want to handle nested arrays, it can get complicated.
For the t...