大约有 41,000 项符合查询结果（耗时：0.0625秒） [XML]
What are named pipes?
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#include <sys/types.h>
#include <sys/stat.h>
int mkfifo(const char *pathname, mode_t mode);
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Difference between Select Unique and Select Distinct
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SELECT UNIQUE is old syntax supported by Oracle's flavor of SQL. It is synonymous with SELECT DISTINCT.
Use SELECT DISTINCT because this is standard SQL, and SELECT UNIQUE is non-standard, and in database brands other than ...
Replace all 0 values to NA
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but what if in the columns 6 and 7 - the datatype is char and no replacement should be done. In my problem, I need replacement only in columns 12 to 15 but the whole df has 21 columns (many must not be touched at all).
– userJT
Feb 20 '15 ...
Set selected option of select box
I want to set a option that was selected previously to be displayed on page load. I tried it with the following code:
16 An...
How to reset postgres' primary key sequence when it falls out of sync?
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-- Login to psql and run the following
-- What is the result?
SELECT MAX(id) FROM your_table;
-- Then run...
-- This should be higher than the last result.
SELECT nextval('your_table_id_seq');
-- If it's not higher... run this set the sequence last to your highest id.
-- (wise to run...
How to filter SQL results in a has-many-through relation
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Results:
Total runtimes from EXPLAIN ANALYZE.
1) Martin 2: 44.594 ms
SELECT s.stud_id, s.name
FROM student s
JOIN student_club sc USING (stud_id)
WHERE sc.club_id IN (30, 50)
GROUP BY 1,2
HAVING COUNT(*) > 1;
2) Erwin 1: 33.217 ms
SELECT s.stud_id, s.name
FROM student s
JOIN ...
Can you create nested WITH clauses for Common Table Expressions?
..., the form of the statement you are looking for would be
WITH x AS
(
SELECT * FROM MyTable
),
y AS
(
SELECT * FROM x
)
SELECT * FROM y
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Which is fastest? SELECT SQL_CALC_FOUND_ROWS FROM `table`, or SELECT COUNT(*)
...irm this - I just updated a query with 4 joins on a 168,000 row database. Selecting just the first 100 rows with a SQL_CALC_FOUND_ROWS took over 20 seconds; using a separate COUNT(*) query took under 5 seconds (for both count + results queries).
– Sam Dufel
Ju...
Semicolon before self-invoking function? [duplicate]
...eventing the ui tabs from working properly.
The error message was Invalid character in jquery.all.ui.js Line: 1. Char: 1.
I stumbled on the semi-colon completely by chance.
When I removed the ; from the ;(function($) it worked, seemingly without side-effects or loss of functionality.
I am using ...
How can I find the latitude and longitude from address?
... while ((b = stream.read()) != -1) {
stringBuilder.append((char) b);
}
} catch (ClientProtocolException e) {
} catch (IOException e) {
}
JSONObject jsonObject = new JSONObject();
try {
jsonObject = new JSONObject(string...