大约有 3,551 项符合查询结果（耗时：0.0269秒） [XML]
How to do SELECT COUNT(*) GROUP BY and ORDER BY in Django?
...ango 2.1.4). In the example, total is the name given and the count used in sql is COUNT('actor') which in this case doesn't matter, but if e.g. values('x', 'y').annotate(count=Count('x')), you'll get COUNT(x), not COUNT(*) or COUNT(x, y), just tried it in ./manage.py shell
– ti...
MySQL: Transactions vs Locking Tables
...rg/wiki/ACID, en.wikipedia.org/wiki/Isolation_(database_systems) and dev.mysql.com/doc/refman/5.1/en/…
– Nikola Svitlica
Sep 6 '15 at 21:52
...
Remove duplicate rows in MySQL
...
This is no longer support in 5.7.4, dev.mysql.com/doc/refman/5.7/en/alter-table.html
– Ray Baxter
Nov 25 '15 at 20:59
|
...
Does Redis persist data?
... power outage..). Redis trades data safety versus performance, like most NoSQL-DBs do.
Most NoSQL-databases follow a concept of replication among multiple nodes to minimize this risk. Redis is considered more a speedy cache instead of a database that guarantees data consistency. Therefore its use c...
switch / pattern matching idea
...s or other involved (often heavily generic) code blocks. Extending LINQ-to-SQL fits in here too.
Tuples, to some extent.
** But do note: The lack of automatic generalization and type inference really hinder the use of even these features. **
All this said, as someone else mentioned, on a small t...
Difference between attr_accessor and attr_accessible
... "users" that contains three columns "firstname", "lastname" and "role" :
SQL instructions :
CREATE TABLE users (
firstname string,
lastname string
role string
);
I assumed that you set the option config.active_record.whitelist_attributes = true in your config/environment/production.rb to ...
windows service vs scheduled task
...ication. OR .. they are continuously-running heavyweight applications like SQL Server, BizTalk, RPC Connections, IIS (even though IIS technically offloads work to other processes).
Personally, I favour scheduled tasks over Window Services for repititive maintenance tasks and applications such as fi...
Entity framework linq query Include() multiple children entities
... .FirstOrDefault(co => co.companyID == companyID);
The Sql generated in both instances is still by no means intuitive, but seems performant enough. I've put a small example on GitHub here
EF Core
EF Core has a new extension method, .ThenInclude(), although the syntax is slightl...
Two single-column indexes vs one two-column index in MySQL?
...
"MySQL can use multiple-column indexes for queries that test all the columns in the index, or queries that test just the first column, the first two columns, the first three columns, and so on. If you specify the columns in the ...
What is scope/named_scope in rails?
...call
Zombie.rotting.fresh.recent.limit(3)
It translates to the below in SQL,
select "zombies.*" from "zombies" where "zombies"."rotting" = 't' and (age<20) order by create_at desc limit 3
Example above is based on rails 4 syntax
...