大约有 45,000 项符合查询结果（耗时：0.0371秒） [XML]
How to Join to first row
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SELECT Orders.OrderNumber, LineItems.Quantity, LineItems.Description
FROM Orders
JOIN LineItems
ON LineItems.LineItemGUID =
(
SELECT TOP 1 LineItemGUID
FROM LineItems
W...
Why does PEP-8 specify a maximum line length of 79 characters? [closed]
...his millennium should Python PEP-8 specify a maximum line length of 79 characters?
9 Answers
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MYSQL OR vs IN performance
...for future Googlers. Total count of returned results is 7264 out of 10000
SELECT * FROM item WHERE id = 1 OR id = 2 ... id = 10000
This query took 0.1239 seconds
SELECT * FROM item WHERE id IN (1,2,3,...10000)
This query took 0.0433 seconds
IN is 3 times faster than OR
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How to drop a table if it exists?
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Is it correct to do the following?
IF EXISTS(SELECT *
FROM dbo.Scores)
DROP TABLE dbo.Scores
No. That will drop the table only if it contains any rows (and will raise an error if the table does not exist).
Instead, for a permanent table you can use
I...
Using Regex to generate Strings rather than match them
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I am not sure Xeger is that good. It cannot handle character classes. It fails to recognize a simple [\w]. A look at the last line of their wiki tells us that.
– John Red
Feb 13 '17 at 12:38
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Checkbox for nullable boolean
...ents your null, whatever the semantics of null means. You could use a <select><option> drop down list to save real estate, but the user has to click twice and the choices aren't nearly as instantaneously clear.
1 0 null
True False Not Set
Yes No Undecided
Male Fema...
C++ new int[0] — will it allocate memory?
...t be reasonable to say that a computer executing a while(!exitRequested) { char *p = new char[0]; delete [] p; } loop without recycling pointers would collapse into dust before it could possibly run out of address space, but on a platform with 32-bit pointers that would be a far less reasonable assu...
Array versus List: When to use which?
...rable is not suitable.
For example,
var str = "This is a string";
var strChars = str.ToCharArray(); // returns array
It is clear that modification of "strChars" will not mutate the original "str" object, irrespective implementation-level knowledge of "str"'s underlying type.
But suppose that
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How do I append one string to another in Python?
... _Py_ForgetReference(v);
*pv = (PyObject *)
PyObject_REALLOC((char *)v, PyBytesObject_SIZE + newsize);
if (*pv == NULL) {
PyObject_Del(v);
PyErr_NoMemory();
return -1;
}
_Py_NewReference(*pv);
sv = (PyBytesObject *) *pv;
Py_SIZE(sv) = newsize;...
C#: Printing all properties of an object [duplicate]
... string)
return string.Format("\"{0}\"", o);
if (o is char && (char)o == '\0')
return string.Empty;
if (o is ValueType)
return (o.ToString());
if (o is IEnumerable)
return ("...");
return ("{ }");
}
}
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