大约有 40,000 项符合查询结果（耗时：0.0544秒） [XML]
Rails find record with zero has_many records associated [duplicate]
..._joins(:photos).where(photos: {id: nil})
which will result in SQL like:
SELECT cities.*
FROM cities LEFT OUTER JOIN photos ON photos.city_id = city.id
WHERE photos.id IS NULL
Using includes:
City.includes(:photos).where(photos: {id: nil})
will have the same result, but will result in much ug...
libpthread.so.0: error adding symbols: DSO missing from command line
...ends on distribution / compiler version:
Ubuntu Saucy:
/usr/bin/ld: /mnt/root/ffmpeg-2.1.1//libavformat/libavformat.a(http.o): undefined reference to symbol 'inflateInit2_'
/lib/x86_64-linux-gnu/libz.so.1: error adding symbols: DSO missing from command line
Ubuntu Raring: (more informative)
/us...
What is a Shim?
...s often times the use and or miss use of different acronyms for the same root concept that causes people confusion. Using the word “shim” to describe the more specific “Structural” design patterns "Proxy", "Adapter" and "Facade" certainly is a clear example of this type of situation. A "sh...
How to delete a row by reference in data.table?
...el.idxs' vs. 'keep.idxs'
keep.idxs <- setdiff(DT[, .I], del.idxs); # select row indexes to keep
cols = names(DT);
DT.subset <- data.table(DT[[1]][keep.idxs]); # this is the subsetted table
setnames(DT.subset, cols[1]);
for (col in cols[2:length(cols)]) {
DT.subset[, (col) := DT[...
DropDownList in MVC 4 with Razor
...
@{
List<SelectListItem> listItems= new List<SelectListItem>();
listItems.Add(new SelectListItem
{
Text = "Exemplo1",
Value = "Exemplo1"
});
listItems.Add(new SelectListItem
{...
Xcode : failed to get the task for process
...two Provisioning Profiles for the same name, Xcode5 will only allow you to select one of them. To work around this, you have to use iPhone Configuration Utility to find the Profile you want, find the 30-digit "Profile Identifier" and copy/paste it into the "Other" value of the Provisioning Profile d...
Mac OSX Lion DNS lookup order [closed]
...
mv /tmp/hosts.$$ /etc/hosts
# fix up permissions while we are at it
chown root:wheel /etc/hosts
chmod 644 /etc/hosts
credit for this fix to:
http://techpatio.com/2011/guides-how-to/fixed-mac-osx-lion-etc-hosts-bugs-dns
s...
SQL Server IN vs. EXISTS Performance
...execution operation, to get their results.
An example:
Query 1 ( plan )
select * from dt where dt.customer in (select c.code from customer c where c.active=0)
Query 2 ( plan )
select * from dt where exists (select 1 from customer c where c.code=dt.customer and c.active=0)
...
Distinct not working with LINQ to Objects
...ey were hit during the foreach loop. This is because the var temp = books.SelectMany(book => book.Authors).Distinct(); returns an IEnumerable, meaning that the request is not executed right away, it is only executed when the data is used. If you would like an example of this firing right away, ...
Could not load file or assembly 'System.Web.Mvc'
...
In VS2010, right click the project in the Solution Explorer and select 'Add Deployable Dependencies'. Then check the MVC related check boxes in the following dialog.
This creates a '_bin_deployableAssemblies' folder in the project which contains all the .dll files mentioned in other answ...