大约有 40,000 项符合查询结果（耗时：0.0425秒） [XML]
MySQL Great Circle Distance (Haversine formula)
...ude, and then asks for only rows where the distance value is less than 25, orders the whole query by distance, and limits it to 20 results. To search by kilometers instead of miles, replace 3959 with 6371.
SELECT id, ( 3959 * acos( cos( radians(37) ) * cos( radians( lat ) )
* cos( radians( lng )...
Difference between Repository and Service Layer?
...ce layer This part operates on view models.
EDIT:
Example of flow for /Orders/ByClient/5 (we want to see order for specific client):
public class OrderController
{
private IOrderService _orderService;
public OrderController(IOrderService orderService)
{
_orderService = orde...
SELECT DISTINCT on one column
... ID, SKU, Product,
ROW_NUMBER() OVER (PARTITION BY PRODUCT ORDER BY ID) AS RowNumber
FROM MyTable
WHERE SKU LIKE 'FOO%') AS a
WHERE a.RowNumber = 1
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What is scope/named_scope in rails?
... scope :fresh, -> { where('age < ?', 25) }
scope :recent, -> { order(created_at: :desc) }
end
And you 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 de...
ActiveRecord OR query
... to use arrays as arguments, the following code works in Rails 4:
query = Order.where(uuid: uuids, id: ids)
Order.where(query.where_values.map(&:to_sql).join(" OR "))
#=> Order Load (0.7ms) SELECT "orders".* FROM "o
How do I remove duplicate items from an array in Perl?
...een; grep !$seen{$_}++, @_ } is a better implementation since it preserves order at no cost. Or even better, use the one from List::MoreUtils.
– ikegami
Nov 6 '12 at 18:51
...
What is a magic number, and why is it bad? [closed]
... update.
For example, let's say you have a Page that displays the last 50 Orders in a "Your Orders" Overview Page. 50 is the Magic Number here, because it's not set through standard or convention, it's a number that you made up for reasons outlined in the spec.
Now, what you do is you have the 50 ...
MySQL Creating tables with Foreign Keys giving errno: 150
...ine a foreign key to reference it. You must define the tables in the right order: Parent table first, then the Child table. If both tables references each other, you must create one table without FK constraints, then create the second table, then add the FK constraint to the first table with ALTER T...
SQLite Concurrent Access
...y fast read/write access, use an in-memory SQLite database. RAM is several orders of magnitude faster than disk.
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How to convert all tables from MyISAM into InnoDB?
...ABASE_NAME
AND `ENGINE` = 'MyISAM'
AND `TABLE_TYPE` = 'BASE TABLE'
ORDER BY table_name DESC;
Then, copy the output and run as a new SQL query.
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