大约有 44,000 项符合查询结果（耗时：0.0291秒） [XML]
Only read selected columns
...from the data.table-package:
You can specify the desired columns with the select parameter from fread from the data.table package. You can specify the columns with a vector of column names or column numbers.
For the example dataset:
library(data.table)
dat <- fread("data.txt", select = c("Year...
Implement paging (skip / take) functionality with this query
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In SQL Server 2012 it is very very easy
SELECT col1, col2, ...
FROM ...
WHERE ...
ORDER BY -- this is a MUST there must be ORDER BY statement
-- the paging comes here
OFFSET 10 ROWS -- skip 10 rows
FETCH NEXT 10 ROWS ONLY; -- take 10 rows
If we want...
PHP code to convert a MySQL query to CSV [closed]
...
SELECT * INTO OUTFILE "c:/mydata.csv"
FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
LINES TERMINATED BY "\n"
FROM my_table;
(the documentation for this is here: http://dev.mysql.com/doc/refman/5.0/en/select.html)
or:...
Unbound classpath container in Eclipse
... or 4. goto Properties -> Java Build Path -> Libraries Tab -> Select the erroneous system library -> Edit (On the right) -> Select alternate JRE -> Finish.
– Rajkiran
Jun 26 '14 at 12:11
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How does MySQL process ORDER BY and LIMIT in a query?
...e LIMIT clause can be used to constrain the number of rows returned by the SELECT statement. LIMIT takes one or two numeric arguments, which must both be nonnegative integer constants (except when using prepared statements).
With two arguments, the first argument specifies the offset of the first ...
python list in sql query as parameter
...I paramstyle.
placeholders= ', '.join(placeholder for unused in l)
query= 'SELECT name FROM students WHERE id IN (%s)' % placeholders
cursor.execute(query, l)
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What is the dual table in Oracle?
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It's a sort of dummy table with a single record used for selecting when you're not actually interested in the data, but instead want the results of some system function in a select statement:
e.g. select sysdate from dual;
See http://www.adp-gmbh.ch/ora/misc/dual.html
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Store query result in a variable using in PL/pgSQL
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I think you're looking for SELECT INTO:
select test_table.name into name from test_table where id = x;
That will pull the name from test_table where id is your function's argument and leave it in the name variable. Don't leave out the table name pre...
IN clause and placeholders
...mes = { "name1", "name2" }; // do whatever is needed first
String query = "SELECT * FROM table"
+ " WHERE name IN (" + makePlaceholders(names.length) + ")";
Cursor cursor = mDb.rawQuery(query, names);
Just make sure to pass exactly as many values as places. The default maximum limit of host pa...
LEFT JOIN only first row
...rtist_id) will be the earliest.
So try something like this (untested...)
SELECT *
FROM feeds f
LEFT JOIN artists a ON a.artist_id = (
SELECT
MIN(fa.artist_id) a_id
FROM feeds_artists fa
WHERE fa.feed_id = f.feed_id
) a
...