大约有 43,000 项符合查询结果（耗时：0.0405秒） [XML]
What are the main performance differences between varchar and nvarchar SQL Server data types?
... AND ([URLa] IS NULL OR [URLu] IS NULL))
);
In this model you only SELECT from the [URL] computed column. For inserting and updating, you determine which field to use by seeing if converting alters the incoming value, which has to be of NVARCHAR type:
INSERT INTO TableName (..., URLa, URLu)...
Reading a string with scanf
...tring[0]). On the other hand, scanf("%s", &string) passes a pointer-to-char[256], but it points to the same place.
Then scanf, when processing the tail of its argument list, will try to pull out a char *. That's the Right Thing when you've passed in string or &string[0], but when you've pas...
How to convert a number to string and vice versa in C++
...ersion succeeded and idx is not 0, idx will contain the index of the first character that was not used for decoding. This could be an index behind the last character.
Finally, the integral types allow to specify a base, for digits larger than 9, the alphabet is assumed (a=10 until z=35). You can fi...
How can I use “sizeof” in a preprocessor macro?
...ou can use following macro:
#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
Usage:
BUILD_BUG_ON( sizeof(someThing) != PAGE_SIZE );
This article explains in details why it works.
3. MS-specific
On Microsoft C++ compiler you can use C_ASSERT macro (requires #include &...
Simple C example of doing an HTTP POST and consuming the response
...lude <netdb.h> /* struct hostent, gethostbyname */
void error(const char *msg) { perror(msg); exit(0); }
int main(int argc,char *argv[])
{
/* first what are we going to send and where are we going to send it? */
int portno = 80;
char *host = "api.somesite.com";
...
print call stack in C or C++
...oid my_func_1(int i) {
(void)i;
my_func_2();
}
int main(int argc, char **argv) {
long long unsigned int n;
if (argc > 1) {
n = strtoul(argv[1], NULL, 0);
} else {
n = 1;
}
for (long long unsigned int i = 0; i < n; ++i) {
my_func_1(1); // l...
How to open, read, and write from serial port in C?
...ed);
tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8; // 8-bit chars
// disable IGNBRK for mismatched speed tests; otherwise receive break
// as \000 chars
tty.c_iflag &= ~IGNBRK; // disable break processing
tty.c_lflag = 0; // n...
What is the size of column of int(11) in mysql in bytes?
...ytes (64 bit).
The length just specifies how many characters to pad when selecting data with the mysql command line client. 12345 stored as int(3) will still show as 12345, but if it was stored as int(10) it would still display as 12345, but you would have the option to pad the first five digits. ...
Differences between INDEX, PRIMARY, UNIQUE, FULLTEXT in MySQL?
...e - which are typically implemented internally using b-trees (allowing for selecting, sorting or ranges starting from left most column) or hash tables (allowing for selection starting from left most column).
Where the other index types are general-purpose, a FULLTEXT index is specialised, in that it...
Using 'starts with' selector on individual class names
...thought of using space in there. Can one use boolean operators in a jquery selector? Ideally, the above would be 'OR' to avoid the (rare and likely avoidable) case where there are more than one class staring with 'apple-'
– DA.
Feb 1 '10 at 17:12
...