大约有 13,000 项符合查询结果（耗时：0.0203秒） [XML]
Apply pandas function to column to create multiple new columns?
...3 1.100880 -0.899120
4 1.017859 -0.982141
Editing for completeness
pd.concat([df, df.textcol.apply(lambda s: pd.Series({'feature1':s+1, 'feature2':s-1}))], axis=1)
textcol feature1 feature2
0 0.626524 1.626524 -0.373476
1 0.119967 1.119967 -0.880033
2 0.803650 1.803650 -0.196350
3 0.10...
LINQ order by null column where order is ascending and nulls should be last
... descending
orderby p.LowestPrice descending
select p;
will be translated by the compiler to
var products = _context.Products
.Where(p => p.ProductTypeId == 1)
.OrderByDescending(p => p.LowestPrice.HasValue)
...
Method Overloading for null argument
... an explicit "null" (yet implicit null type) argument always unambiguously selects a specific overload ??
– peterk
Jul 18 '17 at 21:43
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How do I escape a single quote in SQL Server?
...lue] VARCHAR(200)
)
INSERT INTO @my_table VALUES ('hi, my name''s tim.')
SELECT * FROM @my_table
Results
value
==================
hi, my name's tim.
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In log4j, does checking isDebugEnabled before logging improve performance?
...g statement you will already have the check in place.
2- You don't have to selectively include the statement on "complex" debug statements. All statements are included that way.
3- Calling log.debug executes the following before logging:
if(repository.isDisabled(Level.DEBUG_INT))
retur...
String Concatenation using '+' operator
... see the operators == and != overloaded. So how is it able to perform concatenation for the ' + ' operator?
1 Answer
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Find and extract a number from a string
...n(string.Empty, Regex.Matches(subjectString, @"\d+").OfType<Match>().Select(m => m.Value));
– Markus
Jul 26 '14 at 4:53
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T-SQL CASE Clause: How to specify WHEN NULL
...
Given your query you can also do this:
SELECT first_name + ' ' + ISNULL(last_name, '') AS Name FROM dbo.person
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Dynamic Sorting within SQL Stored Procedures
...eing duplicated twice in the order by, and is a little more readable IMO:
SELECT
s.*
FROM
(SELECT
CASE @SortCol1
WHEN 'Foo' THEN t.Foo
WHEN 'Bar' THEN t.Bar
ELSE null
END as SortCol1,
CASE @SortCol2
WHEN 'Foo' THEN t.Foo
WHEN 'Bar' THEN t.Bar
ELSE...
MySQL error 1449: The user specified as a definer does not exist
...finer for views
Run this SQL to generate the necessary ALTER statements
SELECT CONCAT("ALTER DEFINER=`youruser`@`host` VIEW ",
table_name, " AS ", view_definition, ";")
FROM information_schema.views
WHERE table_schema='your-database-name';
Copy and run the ALTER statements
How to change the...