大约有 40,000 项符合查询结果（耗时：0.0530秒） [XML]
Filter rows which contain a certain string
... @MySchizoBuddy: If the column name contains white space, you can select the variable using backticks. Modifying the example above: mtcars$`my type` <- rownames(mtcars) and then mtcars %>% filter(grepl('Toyota|Mazda', `my type`))
– alex23lemm
Ju...
Case in Select Statement
I have an SQL statement that has a CASE from SELECT and I just can't get it right. Can you guys show me an example of CASE where the cases are the conditions and the results are from the cases. For example:
...
Select objects based on value of variable in object using jq
...
Adapted from this post on Processing JSON with jq, you can use the select(bool) like this:
$ jq '.[] | select(.location=="Stockholm")' json
{
"location": "Stockholm",
"name": "Walt"
}
{
"location": "Stockholm",
"name": "Donald"
}
...
mmap() vs. reading blocks
... way faster. You might write a simple benchmark to prove it to yourself:
char data[0x1000];
std::ifstream in("file.bin");
while (in)
{
in.read(data, 0x1000);
// do something with data
}
versus:
const int file_size=something;
const int page_size=0x1000;
int off=0;
void *data;
int fd = open...
Overloaded method selection based on the parameter's real type
...
I expect the method selection to take
in consideration the real (not the
declared) parameter type. Am I missing
something?
Yes. Your expectation is wrong. In Java, dynamic method dispatch happens only for the object the method is called ...
How do I execute a stored procedure once for each row returned by query?
...
declare @field1 int
declare @field2 int
declare cur CURSOR LOCAL for
select field1, field2 from sometable where someotherfield is null
open cur
fetch next from cur into @field1, @field2
while @@FETCH_STATUS = 0 BEGIN
--execute your sproc on each row
exec uspYourSproc @field1, @fiel...
How should you build your database from source control?
... I'm assuming "look up lists" means the data that is used to populuate <select> boxes? That may not always be possible, since that data might be modified by users (in some way) on production. Keeping backups makes sense in this case. You also suggest recreating the database from scratch as ...
Why is this F# code so slow?
...C# and F#. The C# version is 10 times faster for two strings of about 1500 chars. C#: 69 ms, F# 867 ms. Why? As far as I can tell, they do the exact same thing? Doesn't matter if it is a Release or a Debug build.
...
How to POST raw whole JSON in the body of a Retrofit request?
...erted to a JSONObject (that won't fly with @FieldMap, neither does special chars, some get converted), so following @bnorms hint, and as stated by Square:
An object can be specified for use as an HTTP request body with the @Body annotation.
The object will also be converted using a converter specif...
Passing arguments to C# generic new() of templated type
...itialize object array argument.
var constructorParameters = parameters.Select((paramType, index) =>
// convert the object[index] to the right constructor parameter type.
Expression.Convert(
// read a value from the object[index]
Expression.ArrayAccess(
...