大约有 40,000 项符合查询结果（耗时：0.0344秒） [XML]
How to install mongoDB on windows?
...d as an Administrator. For example, to move the folder to C:\mongodb:
Select Start Menu > All Programs > Accessories.
Right-click Command Prompt and select Run as Administrator from the popup menu.
Issue the following commands:
cd \
move C:\mongodb-win32-* C:\mongodb
...
SQL Server equivalent to MySQL enum data type?
Does SQL Server 2008 have a a data-type like MySQL's enum ?
5 Answers
5
...
How to get last N records with activerecord?
...e-wise - at least not up to Rails 3.1. SomeModel.last(5) will execute the select statement without a limit, returning all records of SomeModel to Ruby as an array, after which Ruby will pick out the last (5) elements. Efficiency-wise, currently, you want to use limit - particularly if you have pote...
How do you uninstall MySQL from Mac OS X?
I accidentally installed the PowerPC version of MySQL on my Intel Mac in Snow Leopard, and it installed without a problem but of course doesn't run properly. I just didn't pay enough attention. Now when I try to install the correct x86 version it says that it can't install because a newer version is...
Delete sql rows where IDs do not have a match from another table
...HERE f.id IS NULL
Using NOT EXISTS:
DELETE FROM BLOB
WHERE NOT EXISTS(SELECT NULL
FROM FILES f
WHERE f.id = fileid)
Using NOT IN:
DELETE FROM BLOB
WHERE fileid NOT IN (SELECT f.id
FROM FILES f)
Warning
Whenever possible, per...
Is there a way to get a collection of all the Models in your Rails app?
....
EDIT: Just for fun, I found a way to list all classes
Module.constants.select { |c| (eval c).is_a? Class }
EDIT: Finally succeeded in listing all models without looking at directories
Module.constants.select do |constant_name|
constant = eval constant_name
if not constant.nil? and constan...
What is the equivalent of 'describe table' in SQL Server?
...
use Select * From INFORMATION_SCHEMA.COLUMNS Where TABLE_NAME = 'TABLENAME' if you don't want to use a stored procedure
– Matias Elorriaga
Aug 4 '14 at 18:21
...
List all sequences in a Postgres db 8.1 with SQL
...
The following query gives names of all sequences.
SELECT c.relname FROM pg_class c WHERE c.relkind = 'S';
Typically a sequence is named as ${table}_id_seq. Simple regex pattern matching will give you the table name.
To get last value of a sequence use the following query:...
App Inventor 2 DynamicComponents 拓展：动态创建AI2组件对象 · App Inventor 2 中文网
...
通过 JSON 字符串创建组件。请参阅Wiki，了解如何创建自己的模板。
从屏幕和组件列表中移除指定 ID 的组件。由于该组件已被删除，因此你可以再次使用该 ID...
What is sharding and why is it important?
... a DBMS for which the locality is quite restricted (say, a user only fires selects with a 'where username = $my_username') it makes sense to put all the usernames starting with A-M on one server and all from N-Z on the other. By this you get near linear scaling for some queries.
Long story short: S...