大约有 41,000 项符合查询结果（耗时：0.0449秒） [XML]
Aggregate function in an SQL update query?
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UPDATE t1
SET t1.field1 = t2.field2Sum
FROM table1 t1
INNER JOIN (select field3, sum(field2) as field2Sum
from table2
group by field3) as t2
on t2.field3 = t1.field3
share
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improve...
add column to mysql table if it does not exist
...rade_database_1_0_to_2_0()
BEGIN
-- rename a table safely
IF NOT EXISTS( (SELECT * FROM information_schema.COLUMNS WHERE TABLE_SCHEMA=DATABASE()
AND TABLE_NAME='my_old_table_name') ) THEN
RENAME TABLE
my_old_table_name TO my_new_table_name,
END IF;
-- add a column safely
IF NO...
Difference between UTF-8 and UTF-16?
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Both UTF-8 and UTF-16 are variable length encodings. However, in UTF-8 a character may occupy a minimum of 8 bits, while in UTF-16 character length starts with 16 bits.
Main UTF-8 pros:
Basic ASCII characters like digits, Latin characters with no accents, etc. occupy one byte which is identical...
Android Eclipse - Could not find *.apk
...is might help you out:
Right-click your app project and go to Properties
Select Android from left-hand side list
Uncheck the "Is Library" checkbox
If your app project relies on library projects which are in your workspace, those of course need to have the "Is Library" box checked.
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jQuery: find element by text
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You can use the :contains selector to get elements based on their content.
Demo here
$('div:contains("test")').css('background-color', 'red');
<div>This is a test</div>
<div>Another Div</div>
<script src="https://...
Inserting multiple rows in mysql
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it's also possible to use INSERT INTO Table SELECT 1, '14/05/2012', 3 UNION SELECT 2, '05/14/2012', 3. of course, this will only be better of the inserted values are coming from different tables.
– Zohar Peled
Jun 1 '15 at 9:18
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List of encodings that Node.js supports
...r.gz
gyp http 200 http://nodejs.org/dist/v0.10.1/node-v0.10.1.tar.gz
xcode-select: Error: No Xcode is selected. Use xcode-select -switch <path-to-xcode>, or see the xcode-select manpage (man xcode-select) for further information.
fs.readFileSync() returns a Buffer if no encoding is specified...
Split a List into smaller lists of N size
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@HaraldCoppoolse the OP didn't ask for selecting, only to split lists
– Phate01
Mar 22 '18 at 16:11
1
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How many database indexes is too many?
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It depends on the operations that occur on the table.
If there's lots of SELECTs and very few changes, index all you like.... these will (potentially) speed the SELECT statements up.
If the table is heavily hit by UPDATEs, INSERTs + DELETEs ... these will be very slow with lots of indexes since t...
How to find children of nodes using BeautifulSoup
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This answers the question how to select <a>link1</a> in the HTML given in the question, but this will FAIL when the first <li class="test"> will contain no <a> elements and there are other li elements with test class that contains<...