大约有 31,400 项符合查询结果（耗时：0.0392秒） [XML]
Want to find records with no associated records in Rails
...).where( :friends => { :person_id => nil } )
For the hmt it's basically the same thing, you rely on the fact that a person with no friends will also have no contacts:
Person.includes(:contacts).where( :contacts => { :person_id => nil } )
Update
Got a question about has_one in the c...
How to calculate date difference in JavaScript?
... 24 hours, and any 'variation' in that due to Daylight Savings Time is actually a switch of timezones. If you don't distinguish between timezones already, trying to figure out a time difference is going to put you in a world of hurt, not least because the DST switchover 'repeats' time. Stay in one t...
What are '$$' used for in PL/pgSQL
...c to function definitions. It can be used to replace single quotes practically anywhere in SQL scripts.
The body of a function happens to be a string literal which has to be enclosed in single quotes. Dollar-quoting is a PostgreSQL-specific substitute for single quotes to avoid quoting issues insi...
Scala type programming resources
...programming, the computation occurs at compile time. I will try to draw parallels between programming at the value-level and programming at the type-level.
Paradigms
There are two main paradigms in type-level programming: "object-oriented" and "functional". Most examples linked to from here follow...
MySQL connection not working: 2002 No such file or directory
...dPress. I have Apache and MySQL running, and the accounts and database are all set up. I tried to make a simple connection:
...
How to construct a REST API that takes an array of id's for the resources
...
If you are passing all your parameters on the URL, then probably comma separated values would be the best choice. Then you would have an URL template like the following:
api.com/users?id=id1,id2,id3,id4,id5
...
Using the rJava package on Win7 64 bit with R
I'm trying to install rJava on a computer with Win 7 64 bit. When I run
12 Answers
1...
Best practices for overriding isEqual: and hash
...ly attributed to Dan Bernstein or Chris Torek. That older algorithm originally floated around on Usenet, and certain attribution is difficult. For example, there is some interesting commentary in this Apache code (search for their names) that references the original source.
Bottom line is, this i...
Eclipse interface icons very small on high resolution screen in Windows 8.1
...rious icons and buttons in the Eclipse (Kepler) interface are very, very small on a laptop with a 3200x1800px screen. The red error decoration that appears to indicate errors on files is difficult to see unless my nose a few cm from the screen.
...
Is there a MySQL command to convert a string to lowercase?
...of keywords that are presently mixed-case. However, I want to convert them all to lowercase. Is there an easy command to do this, either using MySQL or MySQL and PHP?
...