大约有 47,000 项符合查询结果（耗时：0.0311秒） [XML]
Which machine learning classifier to choose, in general? [closed]
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Model selection using cross validation may be what you need.
Cross validation
What you do is simply to split your dataset into k non-overlapping subsets (folds), train a model using k-1 folds and predict its performance using the...
How to do SELECT COUNT(*) GROUP BY and ORDER BY in Django?
...lvaro has answered the Django's direct equivalent for GROUP BY statement:
SELECT actor, COUNT(*) AS total
FROM Transaction
GROUP BY actor
is through the use of values() and annotate() methods as follows:
Transaction.objects.values('actor').annotate(total=Count('actor')).order_by()
However ...
How do I change db schema to dbo
...which will generate a set of ALTER sCHEMA statements for all your talbes:
SELECT 'ALTER SCHEMA dbo TRANSFER ' + TABLE_SCHEMA + '.' + TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'jonathan'
You then have to copy and run the statements in query analyzer.
Here's an older script t...
Copying text with color from Notepad++
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In NPP v6.7.7 you can do this by selecting your text, right clicking on it, select "Plugin commands" and then "Copy text with syntax highlighting".
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Standard alternative to GCC's ##__VA_ARGS__ trick?
...ine REST_HELPER_TWOORMORE(first, ...) , __VA_ARGS__
#define NUM(...) \
SELECT_10TH(__VA_ARGS__, TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE,\
TWOORMORE, TWOORMORE, TWOORMORE, TWOORMORE, ONE, throwaway)
#define SELECT_10TH(a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, ...) a10
int
main...
SQL: How to perform string does not equal
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Try the following query
select * from table
where NOT (tester = 'username')
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What's the fastest way to do a bulk insert into Postgres?
...200, 300]),
UNNEST(ARRAY['a', 'b', 'c'])
);
without VALUES using subselect with additional existance check:
INSERT INTO tablename (fieldname1, fieldname2, fieldname3)
SELECT * FROM (
SELECT UNNEST(ARRAY[1, 2, 3]),
UNNEST(ARRAY[100, 200, 300]),
UNNEST(ARRAY['a', 'b...
Selecting last element in JavaScript array [duplicate]
...gth less 1.
Mozilla Docs on Slice
Performance of the various methods for selecting last array element
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How do I delete a fixed number of rows with sorting in PostgreSQL?
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You could try using the ctid:
DELETE FROM logtable
WHERE ctid IN (
SELECT ctid
FROM logtable
ORDER BY timestamp
LIMIT 10
)
The ctid is:
The physical location of the row version within its table. Note that although the ctid can be used to locate the row version very quickly,...
Indenting code in Sublime text 2?
...gs": { "single_line": false } } will reindent all document without need to select what you want
– Alexis
Apr 22 '15 at 11:43
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