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What are the differences between poll and select?
I am referring to the POSIX standard select and poll system C API calls.
3 Answers
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What's faster, SELECT DISTINCT or GROUP BY in MySQL?
...'t, then use DISTINCT.
GROUP BY in MySQL sorts results. You can even do:
SELECT u.profession FROM users u GROUP BY u.profession DESC
and get your professions sorted in DESC order.
DISTINCT creates a temporary table and uses it for storing duplicates. GROUP BY does the same, but sortes the disti...
Oracle SQL: Update a table with data from another table
...his is called a correlated update
UPDATE table1 t1
SET (name, desc) = (SELECT t2.name, t2.desc
FROM table2 t2
WHERE t1.id = t2.id)
WHERE EXISTS (
SELECT 1
FROM table2 t2
WHERE t1.id = t2.id )
Assuming the join results in a key-pr...
Java: Clear the console
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System.out.println(new String(new char[50]).replace("\0", "\r\n")); will do the job faster and better.
– Aaron Esau
Dec 30 '17 at 0:28
1
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boost多索引容器multi_index_container实战 - C/C++ - 清泛网 - 专注C/C++及内核技术
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typedef std::vector<Person::ptr> Persons;
int main(int argc, char *argv[]) {
if (argc != 2) {
printf("Usage: program count\n");
return 0;
}
PersonContainer container;
IdPersons idPersons;
NamePersons namePersons;
p...
postgresql: INSERT INTO … (SELECT * …)
...ostgres
CREATE TABLE tblA (id serial, time integer);
INSERT INTO tblA
SELECT id, time
FROM dblink('dbname=dbtest', 'SELECT id, time FROM tblB')
AS t(id integer, time integer)
WHERE time > 1000;
TABLE tblA;
id | time
----+------
1 | 5000
2 | 2000
(2 rows)
PostgreSQL has ...
How do I use variables in Oracle SQL Developer?
... other stuff didn't work for me, but this did:
define value1 = 'sysdate'
SELECT &&value1 from dual;
Also it's the slickest way presented here, yet.
(If you omit the "define"-part you'll be prompted for that value)
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Select text on input focus
I have a text input. When the input receives focus I want to select the text inside of the input.
10 Answers
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Insert a string at a specific index
...ice() method changes the content of a string by removing a range of
* characters and/or adding new characters.
*
* @this {String}
* @param {number} start Index at which to start changing the string.
* @param {number} delCount An integer indicating the number of old chars to ...
jQuery count child elements
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You can use .length with just a descendant selector, like this:
var count = $("#selected li").length;
If you have to use .children(), then it's like this:
var count = $("#selected ul").children().length;
You can test both versions here.
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